Programs & Examples On #Edges

What does 'index 0 is out of bounds for axis 0 with size 0' mean?

Essentially it means you don't have the index you are trying to reference. For example:

df = pd.DataFrame()
df['data'][0]=5 #I haven't yet assigned how long df[data] should be!

will give me the error you are referring to, because I haven't told Pandas how long my dataframe is. Whereas if I do the exact same code but I DO assign an index length, I don't get an error:

df = pd.DataFrame(index=[0,1,2,3,4])
df['data'][0]=5 #since I've properly labelled my index, I don't run into this problem!

Hope that answers your question!

What is the difference between 'SAME' and 'VALID' padding in tf.nn.max_pool of tensorflow?

When stride is 1 (more typical with convolution than pooling), we can think of the following distinction:

  • "SAME": output size is the same as input size. This requires the filter window to slip outside input map, hence the need to pad.
  • "VALID": Filter window stays at valid position inside input map, so output size shrinks by filter_size - 1. No padding occurs.

In CSS Flexbox, why are there no "justify-items" and "justify-self" properties?

I know this is not an answer, but I'd like to contribute to this matter for what it's worth. It would be great if they could release justify-self for flexbox to make it truly flexible.

It's my belief that when there are multiple items on the axis, the most logical way for justify-self to behave is to align itself to its nearest neighbours (or edge) as demonstrated below.

I truly hope, W3C takes notice of this and will at least consider it. =)

enter image description here

This way you can have an item that is truly centered regardless of the size of the left and right box. When one of the boxes reaches the point of the center box it will simply push it until there is no more space to distribute.

enter image description here

The ease of making awesome layouts are endless, take a look at this "complex" example.

enter image description here

Error: " 'dict' object has no attribute 'iteritems' "

In Python2, we had .items() and .iteritems() in dictionaries. dict.items() returned list of tuples in dictionary [(k1,v1),(k2,v2),...]. It copied all tuples in dictionary and created new list. If dictionary is very big, there is very big memory impact.

So they created dict.iteritems() in later versions of Python2. This returned iterator object. Whole dictionary was not copied so there is lesser memory consumption. People using Python2 are taught to use dict.iteritems() instead of .items() for efficiency as explained in following code.

import timeit

d = {i:i*2 for i in xrange(10000000)}  
start = timeit.default_timer()
for key,value in d.items():
    tmp = key + value #do something like print
t1 = timeit.default_timer() - start

start = timeit.default_timer()
for key,value in d.iteritems():
    tmp = key + value
t2 = timeit.default_timer() - start


Time with d.items(): 9.04773592949
Time with d.iteritems(): 2.17707300186

In Python3, they wanted to make it more efficient, so moved dictionary.iteritems() to dict.items(), and removed .iteritems() as it was no longer needed.

You have used dict.iteritems() in Python3 so it has failed. Try using dict.items() which has the same functionality as dict.iteritems() of Python2. This is a tiny bit migration issue from Python2 to Python3.

Graphviz's executables are not found (Python 3.4)

For all those who are facing this issue in windows 10 even after trying the above mentiond steps, this worked for me - For Windows 10 users trying to debug this same error, launch CMD as administrator (important!) and run dot -c and then run dot -v
This fixed the issue for me

No such keg: /usr/local/Cellar/git

Had a similar issue while installing "Lua" in OS X using homebrew. I guess it could be useful for other users facing similar issue in homebrew.

On running the command:

$ brew install lua

The command returned an error:

Error: /usr/local/opt/lua is not a valid keg
(in general the error can be of /usr/local/opt/ is not a valid keg

FIXED it by deleting the file/directory it is referring to, i.e., deleting the "/usr/local/opt/lua" file.

root-user # rm -rf /usr/local/opt/lua

And then running the brew install command returned success.

CardView not showing Shadow in Android L

Simply add this tags:


So its become:

    app:contentPadding="1dp" />

How to make a view with rounded corners?

Difference from Jaap van Hengstum's answer:

  1. Use BitmapShader instead of mask bitmap.
  2. Create bitmap only once.
public class RoundedFrameLayout extends FrameLayout {
    private Bitmap mOffscreenBitmap;
    private Canvas mOffscreenCanvas;
    private BitmapShader mBitmapShader;
    private Paint mPaint;
    private RectF mRectF;

    public RoundedFrameLayout(Context context) {

    public RoundedFrameLayout(Context context, AttributeSet attrs) {
        super(context, attrs);

    public RoundedFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);

    private void init() {

    public void draw(Canvas canvas) {
        if (mOffscreenBitmap == null) {
            mOffscreenBitmap = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), Bitmap.Config.ARGB_8888);
            mOffscreenCanvas = new Canvas(mOffscreenBitmap);
            mBitmapShader = new BitmapShader(mOffscreenBitmap, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
            mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
            mRectF = new RectF(0f, 0f, canvas.getWidth(), canvas.getHeight());

        canvas.drawRoundRect(mRectF, 8, 8, mPaint);

Blur the edges of an image or background image with CSS

I'm not entirely sure what visual end result you're after, but here's an easy way to blur an image's edge: place a div with the image inside another div with the blurred image.

Working example here:



<div class="placeholder">
     <!-- blurred background image for blurred edge -->
     <div class="bg-image-blur"></div>
     <!-- same image, no blur -->
     <div class="bg-image"></div>
     <!-- content -->
     <div class="content">Blurred Image Edges</div>


.placeholder {
    margin-right: auto;
    margin-top: 20px;
    width: 200px;
    height: 200px;
    position: relative;
    /* this is the only relevant part for the example */
/* both DIVs have the same image */
 .bg-image-blur, .bg-image {
    background-image: url('');
    width: 100%;
/* blur the background, to make blurred edges that overflow the unblurred image that is on top */
 .bg-image-blur {
    -webkit-filter: blur(20px);
    -moz-filter: blur(20px);
    -o-filter: blur(20px);
    -ms-filter: blur(20px);
    filter: blur(20px);
/* I added this DIV in case you need to place content inside */
 .content {
    position: absolute;
    width: 100%;
    height: 100%;
    color: #fff;
    text-shadow: 0 0 3px #000;
    text-align: center;
    font-size: 30px;

Notice the blurred effect is using the image, so it changes with the image color.

I hope this helps.

Python Key Error=0 - Can't find Dict error in code

The defaultdict solution is better. But for completeness you could also check and create empty list before the append. Add the + lines:

+ if not u in self.adj.keys():
+     self.adj[u] = []

how to draw directed graphs using networkx in python?

I only put this in for completeness. I've learned plenty from marius and mdml. Here are the edge weights. Sorry about the arrows. Looks like I'm not the only one saying it can't be helped. I couldn't render this with ipython notebook I had to go straight from python which was the problem with getting my edge weights in sooner.

import networkx as nx
import numpy as np
import matplotlib.pyplot as plt
import pylab

G = nx.DiGraph()

G.add_edges_from([('A', 'B'),('C','D'),('G','D')], weight=1)
G.add_edges_from([('D','A'),('D','E'),('B','D'),('D','E')], weight=2)
G.add_edges_from([('B','C'),('E','F')], weight=3)
G.add_edges_from([('C','F')], weight=4)

val_map = {'A': 1.0,
                   'D': 0.5714285714285714,
                              'H': 0.0}

values = [val_map.get(node, 0.45) for node in G.nodes()]
                 for u,v,d in G.edges(data=True)])
red_edges = [('C','D'),('D','A')]
edge_colors = ['black' if not edge in red_edges else 'red' for edge in G.edges()]

nx.draw(G,pos, node_color = values, node_size=1500,edge_color=edge_colors,

enter image description here

Getting distance between two points based on latitude/longitude

For people (like me) coming here via search engine and just looking for a solution which works out of the box, I recommend installing mpu. Install it via pip install mpu --user and use it like this to get the haversine distance:

import mpu

# Point one
lat1 = 52.2296756
lon1 = 21.0122287

# Point two
lat2 = 52.406374
lon2 = 16.9251681

# What you were looking for
dist = mpu.haversine_distance((lat1, lon1), (lat2, lon2))
print(dist)  # gives 278.45817507541943.

An alternative package is gpxpy.

If you don't want dependencies, you can use:

import math

def distance(origin, destination):
    Calculate the Haversine distance.

    origin : tuple of float
        (lat, long)
    destination : tuple of float
        (lat, long)

    distance_in_km : float

    >>> origin = (48.1372, 11.5756)  # Munich
    >>> destination = (52.5186, 13.4083)  # Berlin
    >>> round(distance(origin, destination), 1)
    lat1, lon1 = origin
    lat2, lon2 = destination
    radius = 6371  # km

    dlat = math.radians(lat2 - lat1)
    dlon = math.radians(lon2 - lon1)
    a = (math.sin(dlat / 2) * math.sin(dlat / 2) +
         math.cos(math.radians(lat1)) * math.cos(math.radians(lat2)) *
         math.sin(dlon / 2) * math.sin(dlon / 2))
    c = 2 * math.atan2(math.sqrt(a), math.sqrt(1 - a))
    d = radius * c

    return d

if __name__ == '__main__':
    import doctest

The other alternative package is [haversine][1]

from haversine import haversine, Unit

lyon = (45.7597, 4.8422) # (lat, lon)
paris = (48.8567, 2.3508)

haversine(lyon, paris)
>> 392.2172595594006  # in kilometers

haversine(lyon, paris, unit=Unit.MILES)
>> 243.71201856934454  # in miles

# you can also use the string abbreviation for units:
haversine(lyon, paris, unit='mi')
>> 243.71201856934454  # in miles

haversine(lyon, paris, unit=Unit.NAUTICAL_MILES)
>> 211.78037755311516  # in nautical miles

They claim to have performance optimization for distances between all points in two vectors

from haversine import haversine_vector, Unit

lyon = (45.7597, 4.8422) # (lat, lon)
paris = (48.8567, 2.3508)
new_york = (40.7033962, -74.2351462)

haversine_vector([lyon, lyon], [paris, new_york], Unit.KILOMETERS)

>> array([ 392.21725956, 6163.43638211])

How to get coordinates of an svg element?

The way to determine the coordinates depends on what element you're working with. For circles for example, the cx and cy attributes determine the center position. In addition, you may have a translation applied through the transform attribute which changes the reference point of any coordinates.

Most of the ways used in general to get screen coordinates won't work for SVGs. In addition, you may not want absolute coordinates if the line you want to draw is in the same container as the elements it connects.


In your particular code, it's quite difficult to get the position of the node because its determined by a translation of the parent element. So you need to get the transform attribute of the parent node and extract the translation from that.


Working jsfiddle here.

HTML5 Canvas Resize (Downscale) Image High Quality?

Fast canvas resample with good quality:

Update: version 2.0 (faster, web workers + transferable objects) -

 * Hermite resize - fast image resize/resample using Hermite filter. 1 cpu version!
 * @param {HtmlElement} canvas
 * @param {int} width
 * @param {int} height
 * @param {boolean} resize_canvas if true, canvas will be resized. Optional.
function resample_single(canvas, width, height, resize_canvas) {
    var width_source = canvas.width;
    var height_source = canvas.height;
    width = Math.round(width);
    height = Math.round(height);

    var ratio_w = width_source / width;
    var ratio_h = height_source / height;
    var ratio_w_half = Math.ceil(ratio_w / 2);
    var ratio_h_half = Math.ceil(ratio_h / 2);

    var ctx = canvas.getContext("2d");
    var img = ctx.getImageData(0, 0, width_source, height_source);
    var img2 = ctx.createImageData(width, height);
    var data =;
    var data2 =;

    for (var j = 0; j < height; j++) {
        for (var i = 0; i < width; i++) {
            var x2 = (i + j * width) * 4;
            var weight = 0;
            var weights = 0;
            var weights_alpha = 0;
            var gx_r = 0;
            var gx_g = 0;
            var gx_b = 0;
            var gx_a = 0;
            var center_y = (j + 0.5) * ratio_h;
            var yy_start = Math.floor(j * ratio_h);
            var yy_stop = Math.ceil((j + 1) * ratio_h);
            for (var yy = yy_start; yy < yy_stop; yy++) {
                var dy = Math.abs(center_y - (yy + 0.5)) / ratio_h_half;
                var center_x = (i + 0.5) * ratio_w;
                var w0 = dy * dy; //pre-calc part of w
                var xx_start = Math.floor(i * ratio_w);
                var xx_stop = Math.ceil((i + 1) * ratio_w);
                for (var xx = xx_start; xx < xx_stop; xx++) {
                    var dx = Math.abs(center_x - (xx + 0.5)) / ratio_w_half;
                    var w = Math.sqrt(w0 + dx * dx);
                    if (w >= 1) {
                        //pixel too far
                    //hermite filter
                    weight = 2 * w * w * w - 3 * w * w + 1;
                    var pos_x = 4 * (xx + yy * width_source);
                    gx_a += weight * data[pos_x + 3];
                    weights_alpha += weight;
                    if (data[pos_x + 3] < 255)
                        weight = weight * data[pos_x + 3] / 250;
                    gx_r += weight * data[pos_x];
                    gx_g += weight * data[pos_x + 1];
                    gx_b += weight * data[pos_x + 2];
                    weights += weight;
            data2[x2] = gx_r / weights;
            data2[x2 + 1] = gx_g / weights;
            data2[x2 + 2] = gx_b / weights;
            data2[x2 + 3] = gx_a / weights_alpha;
    //clear and resize canvas
    if (resize_canvas === true) {
        canvas.width = width;
        canvas.height = height;
    } else {
        ctx.clearRect(0, 0, width_source, height_source);

    ctx.putImageData(img2, 0, 0);

iOS 7: UITableView shows under status bar

This is how to write it in "Swift" An adjustment to @lipka's answer:

tableView.contentInset = UIEdgeInsetsMake(20.0, 0.0, 0.0, 0.0)

Change values on matplotlib imshow() graph axis

I had a similar problem and google was sending me to this post. My solution was a bit different and less compact, but hopefully this can be useful to someone.

Showing your image with matplotlib.pyplot.imshow is generally a fast way to display 2D data. However this by default labels the axes with the pixel count. If the 2D data you are plotting corresponds to some uniform grid defined by arrays x and y, then you can use matplotlib.pyplot.xticks and matplotlib.pyplot.yticks to label the x and y axes using the values in those arrays. These will associate some labels, corresponding to the actual grid data, to the pixel counts on the axes. And doing this is much faster than using something like pcolor for example.

Here is an attempt at this with your data:

import matplotlib.pyplot as plt

# ... define 2D array hist as you did

plt.imshow(hist, cmap='Reds')
x = np.arange(80,122,2) # the grid to which your data corresponds
nx = x.shape[0]
no_labels = 7 # how many labels to see on axis x
step_x = int(nx / (no_labels - 1)) # step between consecutive labels
x_positions = np.arange(0,nx,step_x) # pixel count at label position
x_labels = x[::step_x] # labels you want to see
plt.xticks(x_positions, x_labels)
# in principle you can do the same for y, but it is not necessary in your case

Colorplot of 2D array matplotlib

Here is the simplest example that has the key lines of code:

import numpy as np 
import matplotlib.pyplot as plt

H = np.array([[1, 2, 3, 4],
          [5, 6, 7, 8],
          [9, 10, 11, 12],
          [13, 14, 15, 16]])

plt.imshow(H, interpolation='none')

enter image description here

Subscript out of bounds - general definition and solution?

Only an addition to the above responses: A possibility in such cases is that you are calling an object, that for some reason is not available to your query. For example you may subset by row names or column names, and you will receive this error message when your requested row or column is not part of the data matrix or data frame anymore. Solution: As a short version of the responses above: you need to find the last working row name or column name, and the next called object should be the one that could not be found. If you run parallel codes like "foreach", then you need to convert your code to a for loop to be able to troubleshoot it.

Center Oversized Image in Div

Building on @yunzen's great answer:

I'm guessing many people searching for this topic are trying use a large image as a "hero" background image, for example on a homepage. In this case, they would often want text to appear over the image and to have it scale down well on mobile devices.

Here is the perfect CSS for such a background image (use it on the <img> tag):

/* Set left edge of inner element to 50% of the parent element */
margin-left: 50%;

/* Move to the left by 50% of own width */
transform: translateX(-50%);

/* Scale image...(101% - instead of 100% - avoids possible 1px white border on left of image due to rounding error */
width: 101%;

/* ...but don't scale it too small on mobile devices - adjust this as needed */
min-width: 1086px;

/* allow content below image to appear on top of image */
position: absolute;
z-index: -1;

/* OPTIONAL - try with/without based on your needs */
top: 0;

/* OPTIONAL - use if your outer element containing the img has "text-align: center" */
left: 0;

SVG gradient using CSS

2019 Answer

With brand new css properties you can have even more flexibility with variables aka custom properties

.shape {

.shape .gradient-bg {
  fill: url(#header-shape-gradient) #fff;

#header-shape-gradient {
  --color-stop: #f12c06;
  --color-bot: #faed34;
<svg viewBox="0 0 100 100" xmlns="" preserveAspectRatio="none" class="shape">
    <linearGradient id="header-shape-gradient" x2="0.35" y2="1">
        <stop offset="0%" stop-color="var(--color-stop)" />
        <stop offset="30%" stop-color="var(--color-stop)" />
        <stop offset="100%" stop-color="var(--color-bot)" />
    <polygon class="gradient-bg" points="0,0 100,0 0,66" />

Just set a named variable for each stop in gradient and then customize as you like in css. You can even change their values dynamically with javascript, like:

document.querySelector('#header-shape-gradient').style.setProperty('--color-stop', "#f5f7f9");

Why doesn't Dijkstra's algorithm work for negative weight edges?

Dijkstra's Algorithm assumes that all edges are positive weighted and this assumption helps the algorithm run faster ( O(V^2) ) than others which take into account the possibility of negative edges (e.g bellman ford's algorithm with complexity of O(V^3)).

This algorithm wont give the correct result in the following case where A is the source vertex:

enter image description here

Also, Dijkstra's Algorithm may sometimes give correct solution even if there are negative edges. Following is an example of such a case:

enter image description here

It will never detect a negative cycle and always produce a result which will always be incorrect if a negative weight cycle is reachable from the source, as in such a case there exists no shortest path in the graph from the source vertex.

Escaping ampersand character in SQL string

set escape on
... node_name = 'Geometric Vectors \& Matrices' ...

or alternatively:

set define off
... node_name = 'Geometric Vectors & Matrices' ...

The first allows you to use the backslash to escape the &.

The second turns off & "globally" (no need to add a backslash anywhere). You can turn it on again by set define on and from that line on the ampersands will get their special meaning back, so you can turn it off for some parts of the script and not for others.

No numeric types to aggregate - change in groupby() behaviour?

I got this error generating a data frame consisting of timestamps and data:

df = pd.DataFrame({'data':value}, index=pd.DatetimeIndex(timestamp))

Adding the suggested solution works for me:

df = pd.DataFrame({'data':value}, index=pd.DatetimeIndex(timestamp), dtype=float))

Thanks Chang She!


2005-01-01 00:10:00  7.53
2005-01-01 00:20:00  7.54
2005-01-01 00:30:00  7.62
2005-01-01 00:40:00  7.68
2005-01-01 00:50:00  7.81
2005-01-01 01:00:00  7.95
2005-01-01 01:10:00  7.96
2005-01-01 01:20:00  7.95
2005-01-01 01:30:00  7.98
2005-01-01 01:40:00  8.06
2005-01-01 01:50:00  8.04
2005-01-01 02:00:00  8.06
2005-01-01 02:10:00  8.12
2005-01-01 02:20:00  8.12
2005-01-01 02:30:00  8.25
2005-01-01 02:40:00  8.27
2005-01-01 02:50:00  8.17
2005-01-01 03:00:00  8.21
2005-01-01 03:10:00  8.29
2005-01-01 03:20:00  8.31
2005-01-01 03:30:00  8.25
2005-01-01 03:40:00  8.19
2005-01-01 03:50:00  8.17
2005-01-01 04:00:00  8.18
2005-01-01 00:00:00  7.636000
2005-01-01 01:00:00  7.990000
2005-01-01 02:00:00  8.165000
2005-01-01 03:00:00  8.236667
2005-01-01 04:00:00  8.180000

Defined Edges With CSS3 Filter Blur

You can try adding the border on an other element:


<div><img src="#" /></div>


div {
   border: 1px solid black;
img {
    filter: blur(5px);

Why is the time complexity of both DFS and BFS O( V + E )

I think every edge has been considered twice and every node has been visited once, so the total time complexity should be O(2E+V).

Webfont Smoothing and Antialiasing in Firefox and Opera

I found the solution with this link :

Step by step method :

  • send your font to a WebFontGenerator and get the zip
  • find the TTF font on the Zip file
  • then, on linux, do this command (or install by apt-get install ttfautohint):
    ttfautohint --strong-stem-width=g neosansstd-black.ttf neosansstd-black.changed.ttf
  • then, one more, send the new TTF file (neosansstd-black.changed.ttf) on the WebFontGenerator
  • you get a perfect Zip with all your webfonts !

I hope this will help.

Twitter Bootstrap modal on mobile devices

For me just $('[data-toggle="modal"]').click(function(){}); is working fine.

Image scaling causes poor quality in firefox/internet explorer but not chrome

This is possible! At least now that css transforms have good support:

You need to use a CSS transform to scale the image - the trick is not just to use a scale(), but also to apply a very small rotation. This triggers IE to use a smoother interpolation of the image:

img {
    /* double desired size */
    width: 56px; 
    height: 56px;

    /* margins to reduce layout size to match the transformed size */ 
    margin: -14px -14px -14px -14px; 

    /* transform to scale with smooth interpolation: */
    transform: scale(0.5) rotate(0.1deg);

How to remove margin space around body or clear default css styles

try to ad the following in your CSS:

body, html{

image processing to improve tesseract OCR accuracy

Three points to improve the readability of the image:

  1. Resize the image with variable height and width(multiply 0.5 and 1 and 2 with image height and width).

  2. Convert the image to Gray scale format(Black and white).

  3. Remove the noise pixels and make more clear(Filter the image).

Refer below code :


public Bitmap Resize(Bitmap bmp, int newWidth, int newHeight)
                Bitmap temp = (Bitmap)bmp;
                Bitmap bmap = new Bitmap(newWidth, newHeight, temp.PixelFormat);
                double nWidthFactor = (double)temp.Width / (double)newWidth;
                double nHeightFactor = (double)temp.Height / (double)newHeight;

                double fx, fy, nx, ny;
                int cx, cy, fr_x, fr_y;
                Color color1 = new Color();
                Color color2 = new Color();
                Color color3 = new Color();
                Color color4 = new Color();
                byte nRed, nGreen, nBlue;

                byte bp1, bp2;

                for (int x = 0; x < bmap.Width; ++x)
                    for (int y = 0; y < bmap.Height; ++y)

                        fr_x = (int)Math.Floor(x * nWidthFactor);
                        fr_y = (int)Math.Floor(y * nHeightFactor);
                        cx = fr_x + 1;
                        if (cx >= temp.Width) cx = fr_x;
                        cy = fr_y + 1;
                        if (cy >= temp.Height) cy = fr_y;
                        fx = x * nWidthFactor - fr_x;
                        fy = y * nHeightFactor - fr_y;
                        nx = 1.0 - fx;
                        ny = 1.0 - fy;

                        color1 = temp.GetPixel(fr_x, fr_y);
                        color2 = temp.GetPixel(cx, fr_y);
                        color3 = temp.GetPixel(fr_x, cy);
                        color4 = temp.GetPixel(cx, cy);

                        // Blue
                        bp1 = (byte)(nx * color1.B + fx * color2.B);

                        bp2 = (byte)(nx * color3.B + fx * color4.B);

                        nBlue = (byte)(ny * (double)(bp1) + fy * (double)(bp2));

                        // Green
                        bp1 = (byte)(nx * color1.G + fx * color2.G);

                        bp2 = (byte)(nx * color3.G + fx * color4.G);

                        nGreen = (byte)(ny * (double)(bp1) + fy * (double)(bp2));

                        // Red
                        bp1 = (byte)(nx * color1.R + fx * color2.R);

                        bp2 = (byte)(nx * color3.R + fx * color4.R);

                        nRed = (byte)(ny * (double)(bp1) + fy * (double)(bp2));

                        bmap.SetPixel(x, y, System.Drawing.Color.FromArgb
                (255, nRed, nGreen, nBlue));


                bmap = SetGrayscale(bmap);
                bmap = RemoveNoise(bmap);

                return bmap;


public Bitmap SetGrayscale(Bitmap img)
                Bitmap temp = (Bitmap)img;
                Bitmap bmap = (Bitmap)temp.Clone();
                Color c;
                for (int i = 0; i < bmap.Width; i++)
                    for (int j = 0; j < bmap.Height; j++)
                        c = bmap.GetPixel(i, j);
                        byte gray = (byte)(.299 * c.R + .587 * c.G + .114 * c.B);
                        bmap.SetPixel(i, j, Color.FromArgb(gray, gray, gray));
                return (Bitmap)bmap.Clone();


public Bitmap RemoveNoise(Bitmap bmap)
                for (var x = 0; x < bmap.Width; x++)
                    for (var y = 0; y < bmap.Height; y++)
                        var pixel = bmap.GetPixel(x, y);
                        if (pixel.R < 162 && pixel.G < 162 && pixel.B < 162)
                            bmap.SetPixel(x, y, Color.Black);
                        else if (pixel.R > 162 && pixel.G > 162 && pixel.B > 162)
                            bmap.SetPixel(x, y, Color.White);
                return bmap;



Why does z-index not work?

If you set position to other value than static but your element's z-index still doesn't seem to work, it may be that some parent element has z-index set.

The stacking contexts have hierarchy, and each stacking context is considered in the stacking order of the parent's stacking context.

So with following html

div { border: 2px solid #000; width: 100px; height: 30px; margin: 10px; position: relative; background-color: #FFF; }_x000D_
#el3 { background-color: #F0F; width: 100px; height: 60px; top: -50px; }
<div id="el1" style="z-index: 5"></div>_x000D_
<div id="el2" style="z-index: 3">_x000D_
  <div id="el3" style="z-index: 8"></div>_x000D_

no matter how big the z-index of el3 will be set, it will always be under el1 because it's parent has lower stacking context. You can imagine stacking order as levels where stacking order of el3 is actually 3.8 which is lower than 5.

If you want to check stacking contexts of parent elements, you can use this:

var el = document.getElementById("#yourElement"); // or use $0 in chrome;
do {
    var styles = window.getComputedStyle(el);
    console.log(styles.zIndex, el);
} while(el.parentElement && (el = el.parentElement));

There is a great article about stacking contexts on MDN

Convert RGBA PNG to RGB with PIL

The transparent parts mostly have RGBA value (0,0,0,0). Since the JPG has no transparency, the jpeg value is set to (0,0,0), which is black.

Around the circular icon, there are pixels with nonzero RGB values where A = 0. So they look transparent in the PNG, but funny-colored in the JPG.

You can set all pixels where A == 0 to have R = G = B = 255 using numpy like this:

import Image
import numpy as np

FNAME = 'logo.png'
img ='RGBA')
x = np.array(img)
r, g, b, a = np.rollaxis(x, axis = -1)
r[a == 0] = 255
g[a == 0] = 255
b[a == 0] = 255
x = np.dstack([r, g, b, a])
img = Image.fromarray(x, 'RGBA')'/tmp/out.jpg')

enter image description here

Note that the logo also has some semi-transparent pixels used to smooth the edges around the words and icon. Saving to jpeg ignores the semi-transparency, making the resultant jpeg look quite jagged.

A better quality result could be made using imagemagick's convert command:

convert logo.png -background white -flatten /tmp/out.jpg

enter image description here

To make a nicer quality blend using numpy, you could use alpha compositing:

import Image
import numpy as np

def alpha_composite(src, dst):
    Return the alpha composite of src and dst.

    src -- PIL RGBA Image object
    dst -- PIL RGBA Image object

    The algorithm comes from
    src = np.asarray(src)
    dst = np.asarray(dst)
    out = np.empty(src.shape, dtype = 'float')
    alpha = np.index_exp[:, :, 3:]
    rgb = np.index_exp[:, :, :3]
    src_a = src[alpha]/255.0
    dst_a = dst[alpha]/255.0
    out[alpha] = src_a+dst_a*(1-src_a)
    old_setting = np.seterr(invalid = 'ignore')
    out[rgb] = (src[rgb]*src_a + dst[rgb]*dst_a*(1-src_a))/out[alpha]
    out[alpha] *= 255
    # astype('uint8') maps np.nan (and np.inf) to 0
    out = out.astype('uint8')
    out = Image.fromarray(out, 'RGBA')
    return out            

FNAME = 'logo.png'
img ='RGBA')
white ='RGBA', size = img.size, color = (255, 255, 255, 255))
img = alpha_composite(img, white)'/tmp/out.jpg')

enter image description here

How does a Breadth-First Search work when looking for Shortest Path?

From tutorial here

"It has the extremely useful property that if all of the edges in a graph are unweighted (or the same weight) then the first time a node is visited is the shortest path to that node from the source node"

How to convert a .eps file to a high quality 1024x1024 .jpg?

For vector graphics, ImageMagick has both a render resolution and an output size that are independent of each other.

Try something like

convert -density 300 image.eps -resize 1024x1024 image.jpg

Which will render your eps at 300dpi. If 300 * width > 1024, then it will be sharp. If you render it too high though, you waste a lot of memory drawing a really high-res graphic only to down sample it again. I don't currently know of a good way to render it at the "right" resolution in one IM command.

The order of the arguments matters! The -density X argument needs to go before image.eps because you want to affect the resolution that the input file is rendered at.

This is not super obvious in the manpage for convert, but is hinted at:


convert [input-option] input-file [output-option] output-file

How to troubleshoot an "AttributeError: __exit__" in multiproccesing in Python?

The error also happens when trying to use the

with multiprocessing.Pool() as pool:
   # ...

with a Python version that is too old (like Python 2.X) and does not support using with together with multiprocessing pools.

(See this answer to another question for more details)

Soft Edges using CSS?

Another option is to use one of my personal favorite CSS tools: box-shadow.

A box shadow is really a drop-shadow on the node. It looks like this:

-moz-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
-webkit-box-shadow: 1px 2px 3px rgba(0,0,0,.5);
box-shadow: 1px 2px 3px rgba(0,0,0,.5);

The arguments are:

1px: Horizontal offset of the effect. Positive numbers shift it right, negative left.
2px: Vertical offset of the effect. Positive numbers shift it down, negative up.
3px: The blur effect.  0 means no blur.
color: The color of the shadow.

So, you could leave your current design, and add a box-shadow like:

box-shadow: 0px -2px 2px rgba(34,34,34,0.6);

This should give you a 'blurry' top-edge.

This website will help with more information:

Negative weights using Dijkstra's Algorithm

"2) Can we use Dijksra’s algorithm for shortest paths for graphs with negative weights – one idea can be, calculate the minimum weight value, add a positive value (equal to absolute value of minimum weight value) to all weights and run the Dijksra’s algorithm for the modified graph. Will this algorithm work?"

This absolutely doesn't work unless all shortest paths have same length. For example given a shortest path of length two edges, and after adding absolute value to each edge, then the total path cost is increased by 2 * |max negative weight|. On the other hand another path of length three edges, so the path cost is increased by 3 * |max negative weight|. Hence, all distinct paths are increased by different amounts.

css transform, jagged edges in chrome

For canvas in Chrome (Version 52)

All listed answers is about images. But my issue is about canvas in chrome (v.52) with transform rotate. They became jagged and all this methods can't help.

Solution that works for me:

  1. Make canvas larger on 1 px for each side => +2 px for width and height;
  2. Draw image with offset + 1px (in position 1,1 instead of 0,0) and fixed size (size of image should be 2px less than size of canvas)
  3. Apply required rotation

So important code blocks:

// Unfixed version
ctx.drawImage(img, 0, 0, 335, 218);
// Fixed version
ctx.drawImage(img, 1, 1, 335, 218);
/* This style should be applied for fixed version */
canvas {
  margin-left: -1px;
<!--Unfixed version-->
<canvas width="335" height="218"></canvas>
<!--Fixed version-->
<canvas width="337" height="220"></canvas>


Note: there is a lot of nested divs because it is simplified version from my project.

This issue is reproduced also for Firefox for me. There is no such issue on Safari and FF with retina.

And other founded solution is to place canvas into div of same size and apply following css to this div:

overflow: hidden;
box-shadow: 0 0 1px rgba(255,255,255,0);
// Or
//outline:1px solid transparent;

And rotation should be applied to this wrapping div. So listed solution is worked but with small modification.

And modified example for such solution is:

Note: See style of div with class 'third'.

How to change the colors of a PNG image easily?

If you are going to be programming an application to do all of this, the process will be something like this:

  1. Convert image from RGB to HSV
  2. adjust H value
  3. Convert image back to RGB
  4. Save image

Best way to create unique token in Rails?

This may be helpful :

SecureRandom.base64(15).tr('+/=', '0aZ')

If you want to remove any special character than put in first argument '+/=' and any character put in second argument '0aZ' and 15 is the length here .

And if you want to remove the extra spaces and new line character than add the things like :

SecureRandom.base64(15).tr('+/=', '0aZ').strip.delete("\n")

Hope this will help to anybody.

How to make a stable two column layout in HTML/CSS

Here you go:

    #left {_x000D_
      width: 200px;_x000D_
      float: left;_x000D_
    #right {_x000D_
      margin-left: 200px;_x000D_
      /* Change this to whatever the width of your left column is*/_x000D_
    .clear {_x000D_
      clear: both;_x000D_
  <div id="container">_x000D_
    <div id="left">_x000D_
    <div id="right">_x000D_
      <div style="background-color: red; height: 10px;">Hello</div>_x000D_
    <div class="clear"></div>_x000D_

See it in action here:

Graph implementation C++

Here is a basic implementation of a graph. Note: I use vertex which is chained to next vertex. And each vertex has a list pointing to adjacent nodes.

#include <iostream>
using namespace std;

// 1 ->2 
// 1->4
// 2 ->3
// 4->3
// 4 -> 5
// Adjacency list
// 1->2->3-null
// 2->3->null

// Structure of a vertex
struct vertex {
   int i;
   struct node *list;
   struct vertex *next;
typedef struct vertex * VPTR;

// Struct of adjacency list
struct node {
    struct vertex * n;
    struct node *next;

typedef struct node * NODEPTR;

class Graph {
        // list of nodes chained together
        VPTR V;
        Graph() {
            V = NULL;
        void addEdge(int, int);
        VPTR  addVertex(int);
        VPTR existVertex(int i);
        void listVertex();

// If vertex exist, it returns its pointer else returns NULL
VPTR Graph::existVertex(int i) {
    VPTR temp  = V;
    while(temp != NULL) {
        if(temp->i == i) {
            return temp;
        temp = temp->next;
   return NULL;
// Add a new vertex to the end of the vertex list
VPTR Graph::addVertex(int i) {
    VPTR temp = new(struct vertex);
    temp->list = NULL;
    temp->i = i;
    temp->next = NULL;

    VPTR *curr = &V;
    while(*curr) {
        curr = &(*curr)->next;
    *curr = temp;
    return temp;

// Add a node from vertex i to j. 
// first check if i and j exists. If not first add the vertex
// and then add entry of j into adjacency list of i
void Graph::addEdge(int i, int j) {

    VPTR v_i = existVertex(i);   
    VPTR v_j = existVertex(j);   
    if(v_i == NULL) {
        v_i = addVertex(i);
    if(v_j == NULL) {
        v_j = addVertex(j);

    NODEPTR *temp = &(v_i->list);
    while(*temp) {
        temp = &(*temp)->next;
    *temp = new(struct node);
    (*temp)->n = v_j;
    (*temp)->next = NULL;
// List all the vertex.
void Graph::listVertex() {
    VPTR temp = V;
    while(temp) {
        cout <<temp->i <<" ";
        temp = temp->next;
    cout <<"\n";


// Client program
int main() {
    Graph G;
    G.addEdge(1, 2);


With the above code, you can expand to do DFS/BFS etc.

What is the maximum number of edges in a directed graph with n nodes?

Undirected is N^2. Simple - every node has N options of edges (himself included), total of N nodes thus N*N

How to fit a smooth curve to my data in R?

LOESS is a very good approach, as Dirk said.

Another option is using Bezier splines, which may in some cases work better than LOESS if you don't have many data points.

Here you'll find an example:

# x, y: the x and y coordinates of the hull points
# n: the number of points in the curve.
bezierCurve <- function(x, y, n=10)
    outx <- NULL
    outy <- NULL

    i <- 1
    for (t in seq(0, 1, length.out=n))
        b <- bez(x, y, t)
        outx[i] <- b$x
        outy[i] <- b$y

        i <- i+1

    return (list(x=outx, y=outy))

bez <- function(x, y, t)
    outx <- 0
    outy <- 0
    n <- length(x)-1
    for (i in 0:n)
        outx <- outx + choose(n, i)*((1-t)^(n-i))*t^i*x[i+1]
        outy <- outy + choose(n, i)*((1-t)^(n-i))*t^i*y[i+1]

    return (list(x=outx, y=outy))

# Example usage
x <- c(4,6,4,5,6,7)
y <- 1:6
plot(x, y, "o", pch=20)
points(bezierCurve(x,y,20), type="l", col="red")

What is the difference between tree depth and height?

Simple Answer:
1. Tree: Number of edges/arc from the root node to the leaf node of the tree is called as the Depth of the Tree.
2. Node: Number of edges/arc from the root node to that node is called as the Depth of that node.

Circular gradient in android

<!-- Drop Shadow Stack -->
    <shape android:shape="oval">
            android:top="1dp" />

        <solid android:color="#00CCCCCC" />

        <corners android:radius="3dp" />
    <shape android:shape="oval">
            android:top="1dp" />

        <solid android:color="#10CCCCCC" />

        <corners android:radius="3dp" />
    <shape android:shape="oval">
            android:top="1dp" />

        <solid android:color="#20CCCCCC" />

        <corners android:radius="3dp" />
    <shape android:shape="oval">
            android:top="1dp" />

        <solid android:color="#30CCCCCC" />

        <corners android:radius="3dp" />
    <shape android:shape="oval">
            android:top="1dp" />

        <solid android:color="#50CCCCCC" />

        <corners android:radius="3dp" />

<!-- Background -->
    <shape android:shape="oval">
        <corners android:radius="3dp" />

<color name="colorAccent_1">#6f64d6</color>
<color name="colorAccent_2">#7668F8</color>
<color name="colorAccent_3">#6F63FF</color>

Making an svg image object clickable with onclick, avoiding absolute positioning

I got this working accross the latest versions of Firefox, Chrome, Safari and Opera.

It relies on a transparent div before the object that has absolute position and set width and height so it covers the object tag below.

Here it is, I've been a bit lazy and used inline styes:

<div id="toolbar" style="width: 600px; height: 100px; position: absolute; z-index: 1;"></div>
<object data="interface.svg" width="600" height="100" type="image/svg+xml">

I used the following JavaScript to hook up an event to it:

<script type="text/javascript">
    var toolbar = document.getElementById("toolbar");
    toolbar.onclick = function (e) {

Aligning textviews on the left and right edges in Android layout

In case you want the left and right elements to wrap content but have the middle space


Java: how to represent graphs?

A simple representation written by 'Robert Sedgwick' and 'Kevin Wayne' is available at

Explanation copied from the above page.

The Graph class represents an undirected graph of vertices named 0 through V - 1.

It supports the following two primary operations: add an edge to the graph, iterate over all of the vertices adjacent to a vertex. It also provides methods for returning the number of vertices V and the number of edges E. Parallel edges and self-loops are permitted. By convention, a self-loop v-v appears in the adjacency list of v twice and contributes two to the degree of v.

This implementation uses an adjacency-lists representation, which is a vertex-indexed array of Bag objects. All operations take constant time (in the worst case) except iterating over the vertices adjacent to a given vertex, which takes time proportional to the number of such vertices.

WPF TabItem Header Styling

While searching for a way to round tabs, I found Carlo's answer and it did help but I needed a bit more. Here is what I put together, based on his work. This was done with MS Visual Studio 2015.

The Code:

<Window x:Class="MainWindow"
        Title="Rounded Tabs Example" Height="550" Width="700" WindowStartupLocation="CenterScreen" FontFamily="DokChampa" FontSize="13.333" ResizeMode="CanMinimize" BorderThickness="0">
        <DropShadowEffect Opacity="0.5"/>
    <Grid Background="#FF423C3C">
        <TabControl x:Name="tabControl" TabStripPlacement="Left" Margin="6,10,10,10" BorderThickness="3">
                <Style TargetType="{x:Type TabItem}">
                    <Setter Property="Template">
                            <ControlTemplate TargetType="{x:Type TabItem}">
                                    <Border Name="Border" Background="#FF6E6C67" Margin="2,2,-8,0" BorderBrush="Black" BorderThickness="1,1,1,1" CornerRadius="10">
                                        <ContentPresenter x:Name="ContentSite" ContentSource="Header" VerticalAlignment="Center" HorizontalAlignment="Center" Margin="2,2,12,2" RecognizesAccessKey="True"/>
                                    <Rectangle Height="100" Width="10" Margin="0,0,-10,0" Stroke="Black" VerticalAlignment="Bottom" HorizontalAlignment="Right" StrokeThickness="0" Fill="#FFD4D0C8"/>
                                    <Trigger Property="IsSelected" Value="True">
                                        <Setter Property="FontWeight" Value="Bold" />
                                        <Setter TargetName="ContentSite" Property="Width" Value="30" />
                                        <Setter TargetName="Border" Property="Background" Value="#FFD4D0C8" />
                                    <Trigger Property="IsEnabled" Value="False">
                                        <Setter TargetName="Border" Property="Background" Value="#FF6E6C67" />
                                    <Trigger Property="IsMouseOver" Value="true">
                                        <Setter Property="FontWeight" Value="Bold" />
                    <Setter Property="HeaderTemplate">
                                <ContentPresenter Content="{TemplateBinding Content}">
                                        <RotateTransform Angle="270" />
                    <Setter Property="Background" Value="#FF6E6C67" />
                    <Setter Property="Height" Value="90" />
                    <Setter Property="Margin" Value="0" />
                    <Setter Property="Padding" Value="0" />
                    <Setter Property="FontFamily" Value="DokChampa" />
                    <Setter Property="FontSize" Value="16" />
                    <Setter Property="VerticalAlignment" Value="Top" />
                    <Setter Property="HorizontalAlignment" Value="Right" />
                    <Setter Property="UseLayoutRounding" Value="False" />
                <Style x:Key="tabGrids">
                    <Setter Property="Grid.Background" Value="#FFE5E5E5" />
                    <Setter Property="Grid.Margin" Value="6,10,10,10" />
            <TabItem Header="Planner">
                <Grid Style="{StaticResource tabGrids}"/>
            <TabItem Header="Section 2">
                <Grid Style="{StaticResource tabGrids}"/>
            <TabItem Header="Section III">
                <Grid Style="{StaticResource tabGrids}"/>
            <TabItem Header="Section 04">
                <Grid Style="{StaticResource tabGrids}"/>
            <TabItem Header="Tools">
                <Grid Style="{StaticResource tabGrids}"/>


enter image description here

Div width 100% minus fixed amount of pixels

While Guffa's answer works in many situations, in some cases you may not want the left and/or right pieces of padding to be the parent of the center div. In these cases, you can use a block formatting context on the center and float the padding divs left and right. Here's the code


<div class="container">
    <div class="left"></div>
    <div class="right"></div>
    <div class="center"></div>

The CSS:

.container {
    width: 100px;
    height: 20px;

.left, .right {
    width: 20px;
    height: 100%;
    float: left;
    background: black;   

.right {
    float: right;

.center {
    overflow: auto;
    height: 100%;
    background: blue;

I feel that this element hierarchy is more natural when compared to nested nested divs, and better represents what's on the page. Because of this, borders, padding, and margin can be applied normally to all elements (ie: this 'naturality' goes beyond style and has ramifications).

Note that this only works on divs and other elements that share its 'fill 100% of the width by default' property. Inputs, tables, and possibly others will require you to wrap them in a container div and add a little more css to restore this quality. If you're unlucky enough to be in that situation, contact me and I'll dig up the css.

jsfiddle here:


CSS 100% height with padding/margin

This is one of the outright idiocies of CSS - I have yet to understand the reasoning (if someone knows, pls. explain).

100% means 100% of the container height - to which any margins, borders and padding are added. So it is effectively impossible to get a container which fills it's parent and which has a margin, border, or padding.

Note also, setting height is notoriously inconsistent between browsers, too.

Another thing I've learned since I posted this is that the percentage is relative the container's length, that is, it's width, making a percentage even more worthless for height.

Nowadays, the vh and vw viewport units are more useful, but still not especially useful for anything other than the top-level containers.

How to create Windows EventLog source from command line?

Try PowerShell 2.0's EventLog cmdlets

Throwing this in for PowerShell 2.0 and upwards:

  • Run New-EventLog once to register the event source:

    New-EventLog -LogName Application -Source MyApp
  • Then use Write-EventLog to write to the log:

        -LogName Application 
        -Source MyApp 
        -EntryType Error 
        -Message "Immunity to iocaine powder not detected, dying now" 
        -EventId 1

Determine if two rectangles overlap each other?

For those of you who are using center points and half sizes for their rectangle data, instead of the typical x,y,w,h, or x0,y0,x1,x1, here's how you can do it:

#include <cmath> // for fabsf(float)

struct Rectangle
    float centerX, centerY, halfWidth, halfHeight;

bool isRectangleOverlapping(const Rectangle &a, const Rectangle &b)
    return (fabsf(a.centerX - b.centerX) <= (a.halfWidth + b.halfWidth)) &&
           (fabsf(a.centerY - b.centerY) <= (a.halfHeight + b.halfHeight)); 

Creating a left-arrow button (like UINavigationBar's "back" style) on a UIToolbar

back arrow

If you don't want to bother with image files, the arrow shape can be drawn in a UIView subclass with the following code:

- (void)drawRect:(CGRect)rect {
    float width = rect.size.width;
    float height = rect.size.height;
    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextMoveToPoint(context, width * 5.0/6.0, height * 0.0/10.0);
    CGContextAddLineToPoint(context, width * 0.0/6.0, height * 5.0/10.0);
    CGContextAddLineToPoint(context, width * 5.0/6.0, height * 10.0/10.0);
    CGContextAddLineToPoint(context, width * 6.0/6.0, height * 9.0/10.0);
    CGContextAddLineToPoint(context, width * 2.0/6.0, height * 5.0/10.0);
    CGContextAddLineToPoint(context, width * 6.0/6.0, height * 1.0/10.0);

    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);

where the arrow view is proportional to a width of 6.0 and a height of 10.0

Good Java graph algorithm library?

JGraph from

Provides a powerfull software to work with graphs (direct or undirect). Also generates Graphivz code, you can see graphics representations. You can put your own code algorithms into pakage, for example: backtracking code. The package provide some algorithms: Dijkstra, backtracking minimun path cost, ect..

What is __declspec and when do I need to use it?

Another example to illustrate the __declspec keyword:

When you are writing a Windows Kernel Driver, sometimes you want to write your own prolog/epilog code sequences using inline assembler code, so you could declare your function with the naked attribute.

__declspec( naked ) int func( formal_parameters ) {}


#define Naked __declspec( naked )
Naked int func( formal_parameters ) {}

Please refer to naked (C++)

What causes: "Notice: Uninitialized string offset" to appear?

Try to test and initialize your arrays before you use them :

if( !isset($catagory[$i]) ) $catagory[$i] = '' ;
if( !isset($task[$i]) ) $task[$i] = '' ;
if( !isset($fullText[$i]) ) $fullText[$i] = '' ;
if( !isset($dueDate[$i]) ) $dueDate[$i] = '' ;
if( !isset($empId[$i]) ) $empId[$i] = '' ;

If $catagory[$i] doesn't exist, you create (Uninitialized) one ... that's all ; => PHP try to read on your table in the address $i, but at this address, there's nothing, this address doesn't exist => PHP return you a notice, and it put nothing to you string. So you code is not very clean, it takes you some resources that down you server's performance (just a very little).

Take care about your MySQL tables default values

if( !isset($dueDate[$i]) ) $dueDate[$i] = '0000-00-00 00:00:00' ;


if( !isset($dueDate[$i]) ) $dueDate[$i] = 'NULL' ;

HTML5 record audio to file

Update now Chrome also supports MediaRecorder API from v47. The same thing to do would be to use it( guessing native recording method is bound to be faster than work arounds), the API is really easy to use, and you would find tons of answers as to how to upload a blob for the server.

Demo - would work in Chrome and Firefox, intentionally left out pushing blob to server...

Code Source

Currently, there are three ways to do it:

  1. as wav[ all code client-side, uncompressed recording], you can check out --> Recorderjs. Problem: file size is quite big, more upload bandwidth required.
  2. as mp3[ all code client-side, compressed recording], you can check out --> mp3Recorder. Problem: personally, I find the quality bad, also there is this licensing issue.
  3. as ogg [ client+ server(node.js) code, compressed recording, infinite hours of recording without browser crash ], you can check out --> recordOpus, either only client-side recording, or client-server bundling, the choice is yours.

    ogg recording example( only firefox):

    var mediaRecorder = new MediaRecorder(stream);
    mediaRecorder.start();  // to start recording.    
    mediaRecorder.stop();   // to stop recording.
    mediaRecorder.ondataavailable = function(e) {
        // do something with the data.

    Fiddle Demo for ogg recording.

How do you implement a re-try-catch?

You can use AOP and Java annotations from jcabi-aspects (I'm a developer):

@RetryOnFailure(attempts = 3, delay = 5)
public String load(URL url) {
  return url.openConnection().getContent();

You could also use @Loggable and @LogException annotations.

how to pass command line arguments to main method dynamically

We can pass string value to main method as argument without using commandline argument concept in java through Netbean

 package MainClass;
 import java.util.Scanner;
 public class CmdLineArgDemo {

 Scanner readData = new Scanner(;   
 System.out.println("Enter any string :");
 String str = readData.nextLine();
 String [] str1 = str.split(" ");
 // System.out.println(str1.length);

   public static void main(String [] args){
      for(int i = 0 ; i<args.length;i++) {
        System.out.print(args[i]+" ");


Enter any string : 
Coders invent Digital World 
Coders invent Digital World

Row count with PDO

Have a look at this link: It is not recommended to use rowCount() in SELECT statements!

How can I generate an apk that can run without server with react-native?

Refer the react-native official documentation on Generating Signed APK

React-Native Generating Signed APK

How do I run SSH commands on remote system using Java?

You may take a look at this Java based framework for remote command execution, incl. via SSH: It relies on two opensource SSH libraries, either JSch (for this implementation even an ECDSA authentication is supported) or Ganymed (one of these two libraries will be enough). At the first glance it might look a bit complex, you'll have to prepare plenty of SSH related classes (providing server and your user details, specifying encryption details, provide OpenSSH compatible private keys, etc., but the SSH itself is quite complex too). On the other hand, the modular design allows for simple inclusion of more SSH libraries, easy implementation of other command's output processing or even interactive classes etc.

Can I make dynamic styles in React Native?

If you are using a screen with filters for example, and you want to set the background of the filter regarding if it was selected or not, you can do:

<TouchableOpacity style={this.props.venueFilters.includes('Bar')?styles.filterBtnActive:styles.filterBtn} onPress={()=>this.setFilter('Bar')}>
<Text numberOfLines={1}>

On which set filter is:

  var filters = this.props.venueFilters;
  console.log(filters.includes('Bar'), "Inclui Bar");
  this.setState(previousState => {
    return { updateFilter: !previousState.updateFilter };

PS: the function this.props.setVenueFilter(filters) is a redux action, and this.props.venueFilters is a redux state.

Cannot add a project to a Tomcat server in Eclipse

  1. Right click on the project name in the Package Explorer view.
  2. Select Properties
  3. Select Project Facets
  4. Click on the Runtimes tab
  5. Check Server
  6. Click on OK

And now:

  1. Right click on the server name in the Servers view
  2. Click on Add and Remove...
  3. Move resources to the right column

How would I extract a single file (or changes to a file) from a git stash?

$ git checkout stash@{0} -- <filename>


  1. Make sure you put space after the "--" and the file name parameter

  2. Replace zero(0) with your specific stash number. To get stash list, use:

    git stash list

Based on Jakub Narebski's answer -- Shorter version

Java : Sort integer array without using Arrays.sort()

int x[] = { 10, 30, 15, 69, 52, 89, 5 };
    int max, temp = 0, index = 0;
    for (int i = 0; i < x.length; i++) {
        int counter = 0;
        max = x[i];
        for (int j = i + 1; j < x.length; j++) {

            if (x[j] > max) {
                max = x[j];
                index = j;

        if (counter > 0) {
            temp = x[index];
            x[index] = x[i];
            x[i] = temp;
    for (int i = 0; i < x.length; i++) {

Resolve promises one after another (i.e. in sequence)?

There's promise-sequence in nodejs.

const promiseSequence = require('promise-sequence');
return promiseSequence( => () => doPromise(el)));

Create directories using make file


_MKDIRS := $(shell for d in $(REQUIRED_DIRS); \
             do                               \
               [[ -d $$d ]] || mkdir -p $$d;  \

$(objects) : $(sources)

As I use Ubuntu, I also needed add this at the top of my Makefile:

SHELL := /bin/bash # Use bash syntax

How to style the option of an html "select" element?

No, it's not possible, as the styling for these elements is handled by the user's OS. MSDN will answer your question here:

Except for background-color and color, style settings applied through the style object for the option element are ignored.

Disable sorting on last column when using jQuery DataTables

The aoColumnDefs' aTargets parameter lets you give indexes offset from the right (use a negative number) as well as from the left. So you could do:

aoColumnDefs: [
     bSortable: false,
     aTargets: [ -1 ]

The equivalent new API (for DataTables 1.10+) would be:

columnDefs: [
   { orderable: false, targets: -1 }

Regular expression to match balanced parentheses

This might help to match balanced parenthesis.


Mobile Redirect using htaccess

For Mobiles like

RewriteCond %{HTTP_REFERER} !^http://(.*)*$ [NC]
RewriteCond %{REQUEST_URI} !^/m/.*$
RewriteCond %{HTTP_USER_AGENT} "android|blackberry|iphone|ipod|iemobile|opera mobile|palmos|webos|googlebot-mobile" [NC]
RewriteRule ^(.*)$ /m/ [L,R=302]

How to extract a floating number from a string

You may like to try something like this which covers all the bases, including not relying on whitespace after the number:

>>> import re
>>> numeric_const_pattern = r"""
...     [-+]? # optional sign
...     (?:
...         (?: \d* \. \d+ ) # .1 .12 .123 etc 9.1 etc 98.1 etc
...         |
...         (?: \d+ \.? ) # 1. 12. 123. etc 1 12 123 etc
...     )
...     # followed by optional exponent part if desired
...     (?: [Ee] [+-]? \d+ ) ?
...     """
>>> rx = re.compile(numeric_const_pattern, re.VERBOSE)
>>> rx.findall(".1 .12 9.1 98.1 1. 12. 1 12")
['.1', '.12', '9.1', '98.1', '1.', '12.', '1', '12']
>>> rx.findall("-1 +1 2e9 +2E+09 -2e-9")
['-1', '+1', '2e9', '+2E+09', '-2e-9']
>>> rx.findall("current level: -2.03e+99db")

For easy copy-pasting:

numeric_const_pattern = '[-+]? (?: (?: \d* \. \d+ ) | (?: \d+ \.? ) )(?: [Ee] [+-]? \d+ ) ?'
rx = re.compile(numeric_const_pattern, re.VERBOSE)
rx.findall("Some example: Jr. it. was .23 between 2.3 and 42.31 seconds")

Increasing the timeout value in a WCF service

Are you referring to the server side or the client side?

For a client, you would want to adjust the sendTimeout attribute of a binding element. For a service, you would want to adjust the receiveTimeout attribute of a binding elemnent.

      <binding name="longTimeoutBinding"
        receiveTimeout="00:10:00" sendTimeout="00:10:00">
        <security mode="None"/>

    <service name="longTimeoutService"
      <endpoint address="net.tcp://localhost/longtimeout/"
        binding="netTcpBinding" bindingConfiguration="longTimeoutBinding" />

Of course, you have to map your desired endpoint to that particular binding.

How to get max value of a column using Entity Framework?

Or you can try this:

(From p In context.Persons Select p Order By age Descending).FirstOrDefault

Is it possible to modify a string of char in C?

No, you cannot modify it, as the string can be stored in read-only memory. If you want to modify it, you can use an array instead e.g.

char a[] = "This is a string";

Or alternately, you could allocate memory using malloc e.g.

char *a = malloc(100);
strcpy(a, "This is a string");
free(a); // deallocate memory once you've done

How to find the maximum value in an array?

If you can change the order of the elements:

 int[] myArray = new int[]{1, 3, 8, 5, 7, };
 int max = myArray[myArray.length - 1];

If you can't change the order of the elements:

int[] myArray = new int[]{1, 3, 8, 5, 7, };
int max = Integer.MIN_VALUE;
for(int i = 0; i < myArray.length; i++) {
      if(myArray[i] > max) {
         max = myArray[i];

Best equivalent VisualStudio IDE for Mac to program .NET/C#

Whilst more of a workaround, if you're running an Intel Mac, you could go the virtualisation route - at least then you can run the same tools.

Fatal error: [] operator not supported for strings

this was available in php 5.6 in php 7+ you should declare the array first

$users = array(); // not $users = ";
$users[] = "762";

How to show the last queries executed on MySQL?

If mysql binlog is enabled you can check the commands ran by user by executing following command in linux console by browsing to mysql binlog directory

mysqlbinlog binlog.000001 >  /tmp/statements.sql


log = /var/log/mysql/mysql.log

or general log will have an effect on performance of mysql

java.lang.OutOfMemoryError: Java heap space

You may want to look at this site to learn more about memory in the JVM:

I have found it useful to use visualgc to watch how the different parts of the memory model is filling up, to determine what to change.

It is difficult to determine which part of memory was filled up, hence visualgc, as you may want to just change the part that is having a problem, rather than just say,

Fine! I will give 1G of RAM to the JVM.

Try to be more precise about what you are doing, in the long run you will probably find the program better for it.

To determine where the memory leak may be you can use unit tests for that, by testing what was the memory before the test, and after, and if there is too big a change then you may want to examine it, but, you need to do the check while your test is still running.

Microsoft Excel ActiveX Controls Disabled?

It was KB2553154. Microsoft needs to release a fix. As a developer of Excel applications we can't go to all our clients computers and delete files off them. We are getting blamed for something Microsoft caused.

python: create list of tuples from lists

You're after the zip function.

Taken directly from the question: How to merge lists into a list of tuples in Python?

>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]
>>> zip(list_a,list_b)
[(1, 5), (2, 6), (3, 7), (4, 8)]

Running bash script from within python

Adding an answer because I was directed here after asking how to run a bash script from python. You receive an error OSError: [Errno 2] file not found if your script takes in parameters. Lets say for instance your script took in a sleep time parameter:" 10") will not work, you must pass it as an array:["", 10])

How do I push a new local branch to a remote Git repository and track it too?

For greatest flexibility, you could use a custom Git command. For example, create the following Python script somewhere in your $PATH under the name git-publish and make it executable:

#!/usr/bin/env python3

import argparse
import subprocess
import sys

def publish(args):
    return['git', 'push', '--set-upstream', args.remote, args.branch]).returncode

def parse_args():
    parser = argparse.ArgumentParser(description='Push and set upstream for a branch')
    parser.add_argument('-r', '--remote', default='origin',
                        help="The remote name (default is 'origin')")
    parser.add_argument('-b', '--branch', help='The branch name (default is whatever HEAD is pointing to)',
    return parser.parse_args()

def main():
    args = parse_args()
    return publish(args)

if __name__ == '__main__':

Then git publish -h will show you usage information:

usage: git-publish [-h] [-r REMOTE] [-b BRANCH]

Push and set upstream for a branch

optional arguments:
  -h, --help            show this help message and exit
  -r REMOTE, --remote REMOTE
                        The remote name (default is 'origin')
  -b BRANCH, --branch BRANCH
                        The branch name (default is whatever HEAD is pointing to)

XML parsing of a variable string in JavaScript

Marknote is a nice lightweight cross-browser JavaScript XML parser. It's object-oriented and it's got plenty of examples, plus the API is documented. It's fairly new, but it has worked nicely in one of my projects so far. One thing I like about it is that it will read XML directly from strings or URLs and you can also use it to convert the XML into JSON.

Here's an example of what you can do with Marknote:

var str = '<books>' +
          '  <book title="A Tale of Two Cities"/>' +
          '  <book title="1984"/>' +

var parser = new marknote.Parser();
var doc = parser.parse(str);

var bookEls = doc.getRootElement().getChildElements();

for (var i=0; i<bookEls.length; i++) {
    var bookEl = bookEls[i];
    // alerts "Element name is 'book' and book title is '...'"
    alert("Element name is '" + bookEl.getName() + 
        "' and book title is '" + 
        bookEl.getAttributeValue("title") + "'"

IF...THEN...ELSE using XML

I don't think you can design the if-then-else construct without taking the design for other constructs into account. I think it's a good principle that each expression should be an element, and its subexpressions should be child elements. There are then questions about whether the name of an element should reflect the type of expression it is, or its role relative to the parent. Or you can do both:


But you can sometimes get away with a design that omits the role-names (condition, then else) and relies on positional significance of elements relative to their parent. It depends a bit on how much you want to keep it concise.

Run-time error '3061'. Too few parameters. Expected 1. (Access 2007)

I got the same error with something like:

Set rs = dbs.OpenRecordset _
( _
  "SELECT Field1, Field2, FieldN " _
  & "FROM Query1 " _
  & "WHERE Query2.Field1 = """ & Value1 & """;" _
, dbOpenSnapshot _

I fixed the error by replacing "Query1" with "Query2"

Python URLLib / URLLib2 POST

u = urllib2.urlopen('http://myserver/inout-tracker', data)
h.request('POST', '/inout-tracker/index.php', data, headers)

Using the path /inout-tracker without a trailing / doesn't fetch index.php. Instead the server will issue a 302 redirect to the version with the trailing /.

Doing a 302 will typically cause clients to convert a POST to a GET request.

CardView not showing Shadow in Android L

Add this line to CardView....

card_view:cardUseCompatPadding="true" //for enable shadow
card_view:cardElevation="9dp" // this for how much shadow you want to show


You can avoid layout_marginTop and layout_marginBottom as shadow itself takes some space to the up and down of it.The amount space defined by how much you will use in card_view:cardElevation="ndp" .

Happy Coding (:

Change user-agent for Selenium web-driver

There is no way in Selenium to read the request or response headers. You could do it by instructing your browser to connect through a proxy that records this kind of information.

Setting the User Agent in Firefox

The usual way to change the user agent for Firefox is to set the variable "general.useragent.override" in your Firefox profile. Note that this is independent from Selenium.

You can direct Selenium to use a profile different from the default one, like this:

from selenium import webdriver
profile = webdriver.FirefoxProfile()
profile.set_preference("general.useragent.override", "whatever you want")
driver = webdriver.Firefox(profile)

Setting the User Agent in Chrome

With Chrome, what you want to do is use the user-agent command line option. Again, this is not a Selenium thing. You can invoke Chrome at the command line with chrome --user-agent=foo to set the agent to the value foo.

With Selenium you set it like this:

from selenium import webdriver
from import Options
opts = Options()
opts.add_argument("user-agent=whatever you want")

driver = webdriver.Chrome(chrome_options=opts)

Both methods above were tested and found to work. I don't know about other browsers.

Getting the User Agent

Selenium does not have methods to query the user agent from an instance of WebDriver. Even in the case of Firefox, you cannot discover the default user agent by checking what general.useragent.override would be if not set to a custom value. (This setting does not exist before it is set to some value.)

Once the browser is started, however, you can get the user agent by executing:

agent = driver.execute_script("return navigator.userAgent")

The agent variable will contain the user agent.

sklearn: Found arrays with inconsistent numbers of samples when calling

I encountered this error because I converted my data to an np.array. I fixed the problem by converting my data to an np.matrix instead and taking the transpose.

ValueError:, np.array(y_list))

Correct:, np.transpose(np.matrix(y_list)))

MySQL: Insert datetime into other datetime field

According to MySQL documentation, you should be able to just enclose that datetime string in single quotes, ('YYYY-MM-DD HH:MM:SS') and it should work. Look here: Date and Time Literals

So, in your case, the command should be as follows:

UPDATE products SET former_date='2011-12-18 13:17:17' WHERE id=1

Is it possible to decrypt MD5 hashes?

In theory it is not possible to decrypt a hash value but you have some dirty techniques for getting the original plain text back.

  1. Bruteforcing: All computer security algorithm suffer bruteforcing. Based on this idea today's GPU employ the idea of parallel programming using which it can get back the plain text by massively bruteforcing it using any graphics processor. This tool hashcat does this job. Last time I checked the cuda version of it, I was able to bruteforce a 7 letter long character within six minutes.
  2. Internet search: Just copy and paste the hash on Google and see If you can find the corresponding plaintext there. This is not a solution when you are pentesting something but it is definitely worth a try. Some websites maintain the hash for almost all the words in the dictionary.

Difference between fprintf, printf and sprintf?

In C, a "stream" is an abstraction; from the program's perspective it is simply a producer (input stream) or consumer (output stream) of bytes. It can correspond to a file on disk, to a pipe, to your terminal, or to some other device such as a printer or tty. The FILE type contains information about the stream. Normally, you don't mess with a FILE object's contents directly, you just pass a pointer to it to the various I/O routines.

There are three standard streams: stdin is a pointer to the standard input stream, stdout is a pointer to the standard output stream, and stderr is a pointer to the standard error output stream. In an interactive session, the three usually refer to your console, although you can redirect them to point to other files or devices:

$ myprog < inputfile.dat > output.txt 2> errors.txt

In this example, stdin now points to inputfile.dat, stdout points to output.txt, and stderr points to errors.txt.

fprintf writes formatted text to the output stream you specify.

printf is equivalent to writing fprintf(stdout, ...) and writes formatted text to wherever the standard output stream is currently pointing.

sprintf writes formatted text to an array of char, as opposed to a stream.

Attempt to set a non-property-list object as an NSUserDefaults

A default object must be a property list—that is, an instance of (or for collections, a combination of instances of): NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary.

If you want to store any other type of object, you should typically archive it to create an instance of NSData. For more details, see Preferences and Settings Programming Guide.

How to add image in a TextView text?

I tried many different solutions and this for me was the best:

SpannableStringBuilder ssb = new SpannableStringBuilder(" Hello world!");
ssb.setSpan(new ImageSpan(context, R.drawable.image), 0, 1, Spannable.SPAN_INCLUSIVE_INCLUSIVE);
tv_text.setText(ssb, TextView.BufferType.SPANNABLE);

This code uses a minimum of memory.

Show an image preview before upload

Without FileReader, we can use URL.createObjectURL method to get the DOMString that represents the object ( our image file ).

Don't forget to validate image extension.

<input type="file" id="files" multiple />
<div class="image-preview"></div>
let file_input = document.querySelector('#files');
let image_preview = document.querySelector('.image-preview');

const handle_file_preview = (e) => {
  let files =;
  let length = files.length;

  for(let i = 0; i < length; i++) {
      let image = document.createElement('img');
      // use the DOMstring for source
      image.src = window.URL.createObjectURL(files[i]);

file_input.addEventListener('change', handle_file_preview);

Writing Python lists to columns in csv

The following code writes python lists into columns in csv

import csv
from itertools import zip_longest
list1 = ['a', 'b', 'c', 'd', 'e']
list2 = ['f', 'g', 'i', 'j']
d = [list1, list2]
export_data = zip_longest(*d, fillvalue = '')
with open('numbers.csv', 'w', encoding="ISO-8859-1", newline='') as myfile:
      wr = csv.writer(myfile)
      wr.writerow(("List1", "List2"))

The output looks like this

enter image description here

What is stdClass in PHP?

Please bear in mind that 2 empty stdClasses are not strictly equal. This is very important when writing mockery expectations.

php > $a = new stdClass();
php > $b = new stdClass();
php > var_dump($a === $b);
php > var_dump($a == $b);
php > var_dump($a);
object(stdClass)#1 (0) {
php > var_dump($b);
object(stdClass)#2 (0) {
php >

php artisan migrate throwing [PDO Exception] Could not find driver - Using Laravel

Install it via this command

sudo apt-get install php5-gd

this worked for me.

How to manually trigger validation with jQuery validate?

Or one can simply use: $('#myElem').valid()

if ($('#myElem').valid()){
   // will also trigger unobtrusive validation only for this element if in place 
   // add your extra logic here to execute only when element is valid

Note that validate() needs to be called on the form before checking it using this method.

Documentation link:

Unable to start debugging on the web server. Could not start ASP.NET debugging VS 2010, II7, Win 7 x64

Check if your website on IIS is not stop.

I fixed it put my web site to run. :D

How to get the bluetooth devices as a list?

Find list of Nearby Bluetooth Devices:

Find Screenshot for the same.

enter image description here

public class MainActivity extends ActionBarActivity {

    private ListView listView;
    private ArrayList<String> mDeviceList = new ArrayList<String>();
    private BluetoothAdapter mBluetoothAdapter;

    protected void onCreate(Bundle savedInstanceState) {

        listView = (ListView) findViewById(;

        mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

        IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
        registerReceiver(mReceiver, filter);


    protected void onDestroy() {

    private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            if (BluetoothDevice.ACTION_FOUND.equals(action)) {
                BluetoothDevice device = intent
                mDeviceList.add(device.getName() + "\n" + device.getAddress());
                Log.i("BT", device.getName() + "\n" + device.getAddress());
                listView.setAdapter(new ArrayAdapter<String>(context,
                        android.R.layout.simple_list_item_1, mDeviceList));


<RelativeLayout xmlns:android=""
    tools:context="com.example.bluetoothdemo.MainActivity" >



Manifest file:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android=""
    android:versionName="1.0" >

        android:targetSdkVersion="21" />

    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />

        android:theme="@style/AppTheme" >
            android:label="@string/app_name" >
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />



Please make sure that you ask Location permission to your user and turn GPS On.

Reason: From Android 6.0 you need Location permission for Bluetooth Discovery.

More reference:



Interface type check with Typescript

Here's the solution I came up with using classes and lodash: (it works!)

// TypeChecks.ts
import _ from 'lodash';

export class BakedChecker {
    private map: Map<string, string>;

    public constructor(keys: string[], types: string[]) { = new Map<string, string>(, i) => {
            return [k, types[i]];
        if ('__optional'))

    getBakedKeys() : string[] {
        return Array.from(;

    getBakedType(key: string) : string {
        return ? : "notfound";

export interface ICheckerTemplate {
    __optional?: any;
    [propName: string]: any;

export function bakeChecker(template : ICheckerTemplate) : BakedChecker {
    let keys = _.keysIn(template);
    if ('__optional' in template) {
        keys = keys.concat(_.keysIn(template.__optional).map(k => '?' + k));
    return new BakedChecker(keys, => {
        const path = k.startsWith('?') ? '__optional.' + k.substr(1) : k;
        const val = _.get(template, path);
        if (typeof val === 'object') return val;
        return typeof val;

export default function checkType<T>(obj: any, template: BakedChecker) : obj is T {
    const o_keys = _.keysIn(obj);
    const t_keys = _.difference(template.getBakedKeys(), ['__optional']);
    return t_keys.every(tk => {
        if (tk.startsWith('?')) {
            const ak = tk.substr(1);
            if (o_keys.includes(ak)) {
                const tt = template.getBakedType(tk);
                if (typeof tt === 'string')
                    return typeof _.get(obj, ak) === tt;
                else {
                    return checkType<any>(_.get(obj, ak), tt);
            return true;
        else {
            if (o_keys.includes(tk)) {
                const tt = template.getBakedType(tk);
                if (typeof tt === 'string')
                    return typeof _.get(obj, tk) === tt;
                else {
                    return checkType<any>(_.get(obj, tk), tt);
            return false;

custom classes:

// MyClasses.ts

import checkType, { bakeChecker } from './TypeChecks';

class Foo {
    a?: string;
    b: boolean;
    c: number;

    public static _checker = bakeChecker({
        __optional: {
            a: ""
        b: false,
        c: 0

class Bar {
    my_string?: string;
    another_string: string;
    foo?: Foo;

    public static _checker = bakeChecker({
        __optional: {
            my_string: "",
            foo: Foo._checker
        another_string: ""

to check the type at runtime:

if (checkType<Bar>(foreign_object, Bar._checker)) { ... }

Read Variable from Web.Config

If you want the basics, you can access the keys via:

string myKey = System.Configuration.ConfigurationManager.AppSettings["myKey"].ToString();
string imageFolder = System.Configuration.ConfigurationManager.AppSettings["imageFolder"].ToString();

To access my web config keys I always make a static class in my application. It means I can access them wherever I require and I'm not using the strings all over my application (if it changes in the web config I'd have to go through all the occurrences changing them). Here's a sample:

using System.Configuration;

public static class AppSettingsGet
    public static string myKey
        get { return ConfigurationManager.AppSettings["myKey"].ToString(); }

    public static string imageFolder
        get { return ConfigurationManager.AppSettings["imageFolder"].ToString(); }

    // I also get my connection string from here
    public static string ConnectionString
       get { return ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString; }

Remove multiple whitespaces

All you need is to run it as follows:

echo preg_replace('/\s{2,}/', ' ', "This is   a Text \n and so on \t     Text text."); // This is a Text and so on Text text.

change Oracle user account status from EXPIRE(GRACE) to OPEN

set long 9999999
set lin 400

This will output something like this:




Just use the first piece of that with alter user instead:


This will put the account back in to OPEN status without changing the password (as long as you cut and paste correctly the hash value from the output of DBMS_METADATA.GET_DDL) and you don't even need to know what the password is.

SQL query for today's date minus two months

TSQL, Alternative using variable declaration. (it might improve Query's readability)

DECLARE @gapPeriod DATETIME = DATEADD(MONTH,-2,GETDATE()); --Period:Last 2 months.

        FB as A
        A.Dte <= @gapPeriod;                               --only older records.

React prevent event bubbling in nested components on click

I had the same issue. I found stopPropagation did work. I would split the list item into a separate component, as so:

class List extends React.Component {
  handleClick = e => {
    // do something

  render() {
    return (
      <ul onClick={this.handleClick}>
        <ListItem onClick={this.handleClick}>Item</ListItem> 

class ListItem extends React.Component {
  handleClick = e => {
    e.stopPropagation();  //  <------ Here is the magic

  render() {
    return (
      <li onClick={this.handleClick}>

Changing selection in a select with the Chosen plugin

From the "Updating Chosen Dynamically" section in the docs: You need to trigger the 'chosen:updated' event on the field

$(document).ready(function() {


    $('button').click(function() {


NOTE: versions prior to 1.0 used the following:


How do I remove background-image in css?


div#a {

Select distinct values from a list using LINQ in C#

You can use GroupBy with anonymous type, and then get First:

list.GroupBy(e => new { 
                          empLoc = e.empLoc, 
                          empPL = e.empPL, 
                          empShift = e.empShift 

    .Select(g => g.First());

Programmatically Hide/Show Android Soft Keyboard

Try this code.

For showing Softkeyboard:

InputMethodManager imm = (InputMethodManager)
if(imm != null){
        imm.toggleSoftInput(InputMethodManager.SHOW_IMPLICIT, 0);

For Hiding SoftKeyboard -

InputMethodManager imm = (InputMethodManager)
if(imm != null){
        imm.toggleSoftInput(0, InputMethodManager.HIDE_IMPLICIT_ONLY);

Git: How to remove remote origin from Git repo

Another method

Cancel local git repository

rm -rf .git

Then; Create git repostory again

git init

Then; Repeat the remote repo connect

git remote add origin REPO_URL

What is the best/safest way to reinstall Homebrew?

Update 10/11/2020 to reflect the latest brew changes.

Brew already provide a command to uninstall itself (this will remove everything you installed with Homebrew):

/bin/bash -c "$(curl -fsSL"

If you failed to run this command due to permission (like run as second user), run again with sudo

Then you can install again:

/bin/bash -c "$(curl -fsSL"

Calling JMX MBean method from a shell script

I've developed jmxfuse which exposes JMX Mbeans as a Linux FUSE filesystem with similar functionality as the /proc fs. It relies on Jolokia as the bridge to JMX. Attributes and operations are exposed for reading and writing.

For example, to read an attribute:

me@oddjob:jmx$ cd log4j/root/attributes
me@oddjob:jmx$ cat priority

to write an attribute:

me@oddjob:jmx$ echo "WARN" > priority

to invoke an operation:

me@oddjob:jmx$ cd Catalina/none/none/WebModule/localhost/helloworld/operations/addParameter
me@oddjob:jmx$ echo "myParam myValue" > invoke

How to Set the Background Color of a JButton on the Mac OS

Have you tried setting JButton.setOpaque(true)?

JButton button = new JButton("test");

How can I return the current action in an ASP.NET MVC view?

In MVC you should provide the View with all data, not let the View collect its own data so what you can do is to set the CSS class in your controller action.

ViewData["CssClass"] = "bold";

and pick out this value from your ViewData in your View

Regex to extract URLs from href attribute in HTML with Python

import re

url = '<p>Hello World</p><a href="">More Examples</a><a href="">Even More Examples</a>'

urls = re.findall('https?://(?:[-\w.]|(?:%[\da-fA-F]{2}))+', url)

>>> print urls
['', '']

Copy directory to another directory using ADD command

Indeed ADD go /usr/local/ will add content of go folder and not the folder itself, you can use Thomasleveil solution or if that did not work for some reason you can change WORKDIR to /usr/local/ then add your directory to it like:

WORKDIR /usr/local/
COPY go go/


WORKDIR /usr/local/go
COPY go ./

But if you want to add multiple folders, it will be annoying to add them like that, the only solution for now as I see it from my current issue is using COPY . . and exclude all unwanted directories and files in .dockerignore, let's say I got folders and files:

- src 
- tmp 
- dist 
- assets 
- go 
- justforfun 
- node_modules 
- scripts 
- .dockerignore 
- Dockerfile 
- headache.lock 
- package.json 

and I want to add src assets package.json justforfun go so:

in Dockerfile:

FROM galaxy:latest

WORKDIR /usr/local/
COPY . .

in .dockerignore file:


Or for more fun (or you like to confuse more people make them suffer as well :P) can be:


In this way you ignore everything, but excluding what you want to be copied or added only from "ignore list".

It is a late answer but adding more ways to do the same covering even more cases.

How to add a second x-axis in matplotlib

I'm forced to post this as an answer instead of a comment due to low reputation. I had a similar problem to Matteo. The difference being that I had no map from my first x-axis to my second x-axis, only the x-values themselves. So I wanted to set the data on my second x-axis directly, not the ticks, however, there is no axes.set_xdata. I was able to use Dhara's answer to do this with a modification:

ax2.lines = []

instead of using:


When in use also cleared my plot from ax1.

Printing list elements on separated lines in Python

Use the splat operator(*)

By default, * operator prints list separated by space. Use sep operator to specify the delimiter

print(*sys.path, sep = "\n")

AngularJS $watch window resize inside directive

You can listen resize event and fire where some dimension change


(function() {
'use strict';

    .directive('resize', ['$window', function ($window) {
        return {
            link: link,
            restrict: 'A'

        function link(scope, element, attrs){
            scope.width = $window.innerWidth;
            function onResize(){
                // uncomment for only fire when $window.innerWidth change   
                // if (scope.width !== $window.innerWidth)
                    scope.width = $window.innerWidth;

            function cleanUp() {
                angular.element($window).off('resize', onResize);

            angular.element($window).on('resize', onResize);
            scope.$on('$destroy', cleanUp);

In html

<div class="row" resize> ,
    <div class="col-sm-2 col-xs-6" ng-repeat="v in tag.vod"> 
        <h4 ng-bind="::v.known_as"></h4>

Controller :

$scope.$watch('width', function(old, newv){
     console.log(old, newv);

How to use .htaccess in WAMP Server?

RewriteEngine on
RewriteBase /basic_test/

RewriteRule ^index.php$ test.php

Submit form using a button outside the <form> tag

In HTML5, there is the form attribute. Basically

<form id="myform" method="get" action="something.php">
    <input type="text" name="name" />

<input type="submit" form="myform" />

Conditionally change img src based on model data

Another alternative (other than binary operators suggested by @jm-) is to use ng-switch:

<span ng-switch on="interface">
   <img ng-switch-when="UP" src='green-checkmark.png'>
   <img ng-switch-default   src='big-black-X.png'>

ng-switch will likely be better/easier if you have more than two images.

Add x and y labels to a pandas plot

what about ...

import pandas as pd
import matplotlib.pyplot as plt

values = [[1,2], [2,5]]

df2 = pd.DataFrame(values, columns=['Type A', 'Type B'], index=['Index 1','Index 2'])

          title='Video streaming dropout by category')
    .set(xlabel='x axis',
         ylabel='y axis'))

Remove 'b' character do in front of a string literal in Python 3

Here u Go

f = open('test.txt','rb+')

Datanode process not running in Hadoop

Delete the datanode under your hadoop folder then rerun

How do you automatically set the focus to a textbox when a web page loads?

If you are using ASP.NET then you can use


in the code on the server, which will add appropriate JavaScript into the page.

Other server-side frameworks may have an equivalent method.

Difference between abstract class and interface in Python

In general, interfaces are used only in languages that use the single-inheritance class model. In these single-inheritance languages, interfaces are typically used if any class could use a particular method or set of methods. Also in these single-inheritance languages, abstract classes are used to either have defined class variables in addition to none or more methods, or to exploit the single-inheritance model to limit the range of classes that could use a set of methods.

Languages that support the multiple-inheritance model tend to use only classes or abstract base classes and not interfaces. Since Python supports multiple inheritance, it does not use interfaces and you would want to use base classes or abstract base classes.

Get first row of dataframe in Python Pandas based on criteria

This tutorial is a very good one for pandas slicing. Make sure you check it out. Onto some snippets... To slice a dataframe with a condition, you use this format:

>>> df[condition]

This will return a slice of your dataframe which you can index using iloc. Here are your examples:

  1. Get first row where A > 3 (returns row 2)

    >>> df[df.A > 3].iloc[0]
    A    4
    B    6
    C    3
    Name: 2, dtype: int64

If what you actually want is the row number, rather than using iloc, it would be df[df.A > 3].index[0].

  1. Get first row where A > 4 AND B > 3:

    >>> df[(df.A > 4) & (df.B > 3)].iloc[0]
    A    5
    B    4
    C    5
    Name: 4, dtype: int64
  2. Get first row where A > 3 AND (B > 3 OR C > 2) (returns row 2)

    >>> df[(df.A > 3) & ((df.B > 3) | (df.C > 2))].iloc[0]
    A    4
    B    6
    C    3
    Name: 2, dtype: int64

Now, with your last case we can write a function that handles the default case of returning the descending-sorted frame:

>>> def series_or_default(X, condition, default_col, ascending=False):
...     sliced = X[condition]
...     if sliced.shape[0] == 0:
...         return X.sort_values(default_col, ascending=ascending).iloc[0]
...     return sliced.iloc[0]
>>> series_or_default(df, df.A > 6, 'A')
A    5
B    4
C    5
Name: 4, dtype: int64

As expected, it returns row 4.

How do I get the current location of an iframe?

I did some tests in Firefox 3 comparing the value of .src and .documentWindow.location.href in an iframe. (Note: The documentWindow is called contentDocument in Chrome, so instead of .documentWindow.location.href in Chrome it will be .contentDocument.location.href.)

src is always the last URL that was loaded in the iframe without user interaction. I.e., it contains the first value for the URL, or the last value you set up with Javascript from the containing window doing:

document.getElementById("myiframe").src = '';

If the user navigates inside the iframe, you can't anymore access the value of the URL using src. In the previous example, if the user goes away from and you do:


You will still get "".

documentWindow.location.href is only available if the iframe contains a page in the same domain as the containing window, but if it's available it always contains the right value for the URL, even if the user navigates in the iframe.

If you try to access documentWindow.location.href (or anything under documentWindow) and the iframe is in a page that doesn't belong to the domain of the containing window, it will raise an exception:

document.getElementById("myiframe").src = '';
Error: Permission denied to get property Location.href

I have not tested any other browser.

Hope it helps!

Replace Div with another Div


<div id="replaceMe">i need to be replaced</div>
<div id="iamReplacement">i am replacement</div>



ImportError: No module named 'MySQL'

I have found another reason: If your program file's path contains space or special characters, then you'd get this error.

Generate random number between two numbers in JavaScript

ES6 / Arrow functions version based on Francis' code (i.e. the top answer):

const randomIntFromInterval = (min, max) => Math.floor(Math.random() * (max - min + 1) + min);

How to force Hibernate to return dates as java.util.Date instead of Timestamp?

A simple alternative to using a custom UserType is to construct a new java.util.Date in the setter for the date property in your persisted bean, eg:

import java.util.Date;
import javax.persistence.Entity;
import javax.persistence.Column;

public class Purchase {

    private Date date;

    public Date getDate() {

    public void setDate(Date date) {
        // force java.sql.Timestamp to be set as a java.util.Date = new Date(date.getTime());


How to set ssh timeout?

try this:

timeout 5 ssh user@ip

timeout executes the ssh command (with args) and sends a SIGTERM if ssh doesn't return after 5 second. for more details about timeout, read this document:

or you can use the param of ssh:

ssh -o ConnectTimeout=3 user@ip

How to get POST data in WebAPI?

After spending a good bit of time today trying to wrap my brain around the (significant but powerful) paradigm shift between old ways of processing web form data and how it is done with WebAPI, I thought I'd add my 2 cents to this discussion.

What I wanted to do (which is pretty common for web form processing of a POST) is to be able to grab any of the form values I want, in any order. Say like you can do if you have your data in a System.Collections.Specialized.NameValueCollection. But turns out, in WebAPI, the data from a POST comes back at you as a stream. So you can't directly do that.

But there is a cool little class named FormDataCollection (in System.Net.Http.Formatting) and what it will let you do is iterate through your collection once.

So I wrote a simple utility method that will run through the FormDataCollection once and stick all the values into a NameValueCollection. Once this is done, you can jump all around the data to your hearts content.

So in my ApiController derived class, I have a post method like this:

    public void Post(FormDataCollection formData)
        NameValueCollection valueMap = WebAPIUtils.Convert(formData);

        ... my code that uses the data in the NameValueCollection

The Convert method in my static WebAPIUtils class looks like this:

    /// <summary>
    /// Copy the values contained in the given FormDataCollection into 
    /// a NameValueCollection instance.
    /// </summary>
    /// <param name="formDataCollection">The FormDataCollection instance. (required, but can be empty)</param>
    /// <returns>The NameValueCollection. Never returned null, but may be empty.</returns>
    public static NameValueCollection Convert(FormDataCollection formDataCollection)
        Validate.IsNotNull("formDataCollection", formDataCollection);

        IEnumerator<KeyValuePair<string, string>> pairs = formDataCollection.GetEnumerator();

        NameValueCollection collection = new NameValueCollection();

        while (pairs.MoveNext())
            KeyValuePair<string, string> pair = pairs.Current;

            collection.Add(pair.Key, pair.Value);

        return collection;

Hope this helps!

Getting error "No such module" using Xcode, but the framework is there

My issue was with multiple targets. I solved it with below links: configure pod file right way and fix build settings

Hope some one will find it helpful.

using sql count in a case statement

    COUNT(CASE WHEN rsp_ind = 0 then 1 ELSE NULL END) as "New",
    COUNT(CASE WHEN rsp_ind = 1 then 1 ELSE NULL END) as "Accepted"
from tb_a

You can see the output for this request HERE

PHP CURL Enable Linux

If it's php 7 on ubuntu, try this

apt-get install php7.0-curl
/etc/init.d/apache2 restart

Finding row index containing maximum value using R

See ?which.max

> which.max( matrix[,2] )
[1] 2

What is Java String interning?

String interning is an optimization technique by the compiler. If you have two identical string literals in one compilation unit then the code generated ensures that there is only one string object created for all the instance of that literal(characters enclosed in double quotes) within the assembly.

I am from C# background, so i can explain by giving a example from that:

object obj = "Int32";
string str1 = "Int32";
string str2 = typeof(int).Name;

output of the following comparisons:

Console.WriteLine(obj == str1); // true
Console.WriteLine(str1 == str2); // true    
Console.WriteLine(obj == str2); // false !?

Note1:Objects are compared by reference.

Note2:typeof(int).Name is evaluated by reflection method so it does not gets evaluated at compile time. Here these comparisons are made at compile time.

Analysis of the Results: 1) true because they both contain same literal and so the code generated will have only one object referencing "Int32". See Note 1.

2) true because the content of both the value is checked which is same.

3) FALSE because str2 and obj does not have the same literal. See Note 2.

How to skip the first n rows in sql query

Do you want something like in LINQ skip 5 and take 10?


This approach will work in any SQL version.

Oracle SQL Developer: Failure - Test failed: The Network Adapter could not establish the connection?

I just had same issue when I installed the oracle 11g and then creating the database.

I don't even know that the listener has to create manually. Hence, I open Net Configuration Assistant and manually create the listener.

And I can connect the database that I created locally through sql developer.

Is there a way to catch the back button event in javascript?

I have created a solution which may be of use to some people. Simply include the code on your page, and you can write your own function that will be called when the back button is clicked.

I have tested in IE, FF, Chrome, and Safari, and are all working. The solution I have works based on iframes without the need for constant polling, in IE and FF, however, due to limitations in other browsers, the location hash is used in Safari.

Changing the selected option of an HTML Select element

None of the examples using jquery in here are actually correct as they will leave the select displaying the first entry even though value has been changed.

The right way to select Alaska and have the select show the right item as selected using:

<select id="state">
    <option value="AL">Alabama</option>
    <option value="AK">Alaska</option>
    <option value="AZ">Arizona</option>

With jquery would be:


Get JSF managed bean by name in any Servlet related class

I had same requirement.

I have used the below way to get it.

I had session scoped bean.

class ManagedBean {

I have used the below code in my servlet doPost() method.

ManagedBean mb = (ManagedBean) request.getSession().getAttribute("mb");

it solved my problem.

The term 'Get-ADUser' is not recognized as the name of a cmdlet

If you don't see the Active Directory, it's because you did not install AD LS Users and Computer Feature. Go to Manage - Add Roles & Features. Within Add Roles and Features Wizard, on Features tab, select Remote Server Administration Tools, select - Role Admininistration Tools - Select AD DS and DF LDS Tools.

After that, you can see the PS Active Directory package.

Named parameters in JDBC

Plain vanilla JDBC does not support named parameters.

If you are using DB2 then using DB2 classes directly:

  1. Using named parameter markers with PreparedStatement objects
  2. Using named parameter markers with CallableStatement objects

How to make Sonar ignore some classes for codeCoverage metric?

I had to struggle for a little bit but I found a solution, I added


and the coverage metric was cancelled from the dashboard at all, so I realized that the problem was the path I was passing, not the property. In my case the path to exclude was java/org/acme/exceptions, so I used :


and it worked, but since I don't have sub-folders it also works with


How do I change the database name using MySQL?

Unfortunately, MySQL does not explicitly support that (except for dumping and reloading database again).


13.1.32. RENAME DATABASE Syntax

RENAME {DATABASE | SCHEMA} db_name TO new_db_name;

This statement was added in MySQL 5.1.7 but was found to be dangerous and was removed in MySQL 5.1.23. ... Use of this statement could result in loss of database contents, which is why it was removed. Do not use RENAME DATABASE in earlier versions in which it is present.

How to access elements of a JArray (or iterate over them)

There is a much simpler solution for that.
Actually treating the items of JArray as JObject works.
Here is an example:
Let's say we have such array of JSON objects:

JArray jArray = JArray.Parse(@"[
                ""name"": ""Croke Park II"",
                ""url"": """",
                ""promoted_content"": null,
                ""query"": ""%22Croke+Park+II%22"",
                ""events"": null
                ""name"": ""Siptu"",
                ""url"": """",
                ""promoted_content"": null,
                ""query"": ""Siptu"",
                ""events"": null

To get access each item we just do the following:

foreach (JObject item in jArray)
    string name = item.GetValue("name").ToString();
    string url = item.GetValue("url").ToString();
    // ...

Declaring variables in Excel Cells

You can name cells. This is done by clicking the Name Box (that thing next to the formula bar which says "A1" for example) and typing a name, such as, "myvar". Now you can use that name instead of the cell reference:

= myvar*25

How to resize images proportionally / keeping the aspect ratio?

$('#productThumb img').each(function() {
    var maxWidth = 140; // Max width for the image
    var maxHeight = 140;    // Max height for the image
    var ratio = 0;  // Used for aspect ratio
    var width = $(this).width();    // Current image width
    var height = $(this).height();  // Current image height
    // Check if the current width is larger than the max
    if(width > height){
        height = ( height / width ) * maxHeight;

    } else if(height > width){
        maxWidth = (width/height)* maxWidth;
    $(this).css("width", maxWidth); // Set new width
    $(this).css("height", maxHeight);  // Scale height based on ratio

Google maps API V3 - multiple markers on exact same spot

For situations where there are multiple services in the same building you could offset the markers just a little, (say by .001 degree), in a radius from the actual point. This should also produce a nice visual effect.

how to write an array to a file Java

If you're okay with Apache commons lib

outputWriter.write(ArrayUtils.join(array, ","));

Why am I getting "Received fatal alert: protocol_version" or "peer not authenticated" from Maven Central?

For setting java properties on Windows app server:

  • configure tomcat > run as admin
  • then add Java opts:

  • restart service.

Where should I put the file?

There are many ways to do it:

Way1: If you are trying in maven project without Using PropertyConfigurator

First: check for resources directory at scr/main

  if available,
       then: create a .properties file and add all configuration details.
       then: create a directory named resources and a file with .properties     
write your configuration code/details.

follows the screenshot:

![enter image description here

Way2: If you are trying with Properties file for java/maven project Use PropertyConfigurator

Place properties file anywhere in project and give the correct path. say: src/javaLog4jProperties/




enter image description here

Way3: If you are trying with xml on java/maven project Use DOMConfigurator

Place properties file anywhere in project and give correct path. say: src/javaLog4jProperties/log4j.xml




enter image description here

How to cast the size_t to double or int C++

Assuming that the program cannot be redesigned to avoid the cast (ref. Keith Thomson's answer):

To cast from size_t to int you need to ensure that the size_t does not exceed the maximum value of the int. This can be done using std::numeric_limits:

int SizeTToInt(size_t data)
    if (data > std::numeric_limits<int>::max())
        throw std::exception("Invalid cast.");
    return std::static_cast<int>(data);

If you need to cast from size_t to double, and you need to ensure that you don't lose precision, I think you can use a narrow cast (ref. Stroustrup: The C++ Programming Language, Fourth Edition):

template<class Target, class Source>
Target NarrowCast(Source v)
    auto r = static_cast<Target>(v);
    if (static_cast<Source>(r) != v)
        throw RuntimeError("Narrow cast failed.");
    return r;

I tested using the narrow cast for size_t-to-double conversions by inspecting the limits of the maximum integers floating-point-representable integers (code uses googletest):

EXPECT_EQ(static_cast<size_t>(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() - 2 })), size_t{ IntegerRepresentableBoundary() - 2 });
EXPECT_EQ(static_cast<size_t>(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() - 1 })), size_t{ IntegerRepresentableBoundary() - 1 });
EXPECT_EQ(static_cast<size_t>(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() })), size_t{ IntegerRepresentableBoundary() });
EXPECT_THROW(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() + 1 }), std::exception);
EXPECT_EQ(static_cast<size_t>(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() + 2 })), size_t{ IntegerRepresentableBoundary() + 2 });
EXPECT_THROW(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() + 3 }), std::exception);
EXPECT_EQ(static_cast<size_t>(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() + 4 })), size_t{ IntegerRepresentableBoundary() + 4 });
EXPECT_THROW(NarrowCast<double>(size_t{ IntegerRepresentableBoundary() + 5 }), std::exception);


constexpr size_t IntegerRepresentableBoundary()
    static_assert(std::numeric_limits<double>::radix == 2, "Method only valid for binary floating point format.");
    return size_t{2} << (std::numeric_limits<double>::digits - 1);

That is, if N is the number of digits in the mantissa, for doubles smaller than or equal to 2^N, integers can be exactly represented. For doubles between 2^N and 2^(N+1), every other integer can be exactly represented. For doubles between 2^(N+1) and 2^(N+2) every fourth integer can be exactly represented, and so on.

Bootstrap 3 - jumbotron background image effect

I think what you are looking for is to keep the background image fixed and just move the content on scroll. For that you have to simply use the following css property :

background-attachment: fixed;

Why is the Java main method static?

It is just a convention. The JVM could certainly deal with non-static main methods if that would have been the convention. After all, you can define a static initializer on your class, and instantiate a zillion objects before ever getting to your main() method.

How do you run multiple programs in parallel from a bash script?

I had a similar situation recently where I needed to run multiple programs at the same time, redirect their outputs to separated log files and wait for them to finish and I ended up with something like that:


# Add the full path processes to run to the array
PROCESSES_TO_RUN=("/home/joao/Code/test/prog_1/prog1" \
# You can keep adding processes to the array...

for i in ${PROCESSES_TO_RUN[@]}; do
    ${i%/*}/./${i##*/} > ${i}.log 2>&1 &
    # ${i%/*} -> Get folder name until the /
    # ${i##*/} -> Get the filename after the /

# Wait for the processes to finish


How to run a program in Atom Editor?

For C/C++ programs there's very good package gpp-compiler.


  • To compile and run: F5
  • To debug: F6

MacOS Xcode CoreSimulator folder very big. Is it ok to delete content?

That directory is part of your user data and you can delete any user data without affecting Xcode seriously. You can delete the whole CoreSimulator/ directory. Xcode will recreate fresh instances there for you when you do your next simulator run. If you can afford losing any previous simulator data of your apps this is the easy way to get space.

Update: A related useful app is "DevCleaner for Xcode"

What is the difference between JDK and JRE?

JDK includes the JRE plus command-line development tools such as compilers and debuggers that are necessary or useful for developing applets and applications.

JRE is basically the Java Virtual Machine where your Java programs run on. It also includes browser plugins for Applet execution.

JDK is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.

So, Basically JVM < JRE < JDK as per @Jaimin Patel said.

"Could not find bundler" error

According to this answer to a similar question, it should be enough:

rvmsudo gem install bundler.


How can I insert data into a MySQL database?

Here is OOP:

import MySQLdb

class Database:

    host = 'localhost'
    user = 'root'
    password = '123'
    db = 'test'

    def __init__(self):
        self.connection = MySQLdb.connect(, self.user, self.password, self.db)
        self.cursor = self.connection.cursor()

    def insert(self, query):

    def query(self, query):
        cursor = self.connection.cursor( MySQLdb.cursors.DictCursor )

        return cursor.fetchall()

    def __del__(self):

if __name__ == "__main__":

    db = Database()

    #CleanUp Operation
    del_query = "DELETE FROM basic_python_database"

    # Data Insert into the table
    query = """
        INSERT INTO basic_python_database
        (`name`, `age`)
        ('Mike', 21),
        ('Michael', 21),
        ('Imran', 21)

    # db.query(query)

    # Data retrieved from the table
    select_query = """
        SELECT * FROM basic_python_database
        WHERE age = 21

    people = db.query(select_query)

    for person in people:
        print "Found %s " % person['name']

How to declare a vector of zeros in R

X <- c(1:3)*0

Maybe this is not the most efficient way to initialize a vector to zero, but this requires to remember only the c() function, which is very frequently cited in tutorials as a usual way to declare a vector.

As as side-note: To someone learning her way into R from other languages, the multitude of functions to do same thing in R may be mindblowing, just as demonstrated by the previous answers here.

Examples of Algorithms which has O(1), O(n log n) and O(log n) complexities

O(1): finding the best next move in Chess (or Go for that matter). As the number of game states is finite it's only O(1) :-)

How to draw a standard normal distribution in R

Something like this perhaps?

x<-rnorm(100000,mean=10, sd=2)
abline(v=10, lwd=5)
abline(v=c(4,6,8,12,14,16), lwd=3,lty=3)

CSS Custom Dropdown Select that works across all browsers IE7+ FF Webkit

I was also having a similar problem. Finally found one solution at


1) For Firefox support there is special CSS handling for SELECT element's parent, please take a closer look.

2) Download the down.png from Down.png

CSS code

        /* For Firefox browser we need to style for SELECT element parent. */

        @-moz-document url-prefix() {

            /* Please note this is the parent of "SELECT" element */

            .select-example {   
                background: url('');
                background-color: #FFFFFF;
                border: 1px solid #9e9e9e;
                background-size: auto 6px;
                background-repeat: no-repeat;
                background-position: 96% 13px;

        /* IE specific styles */
        @media all and (-ms-high-contrast: none), (-ms-high-contrast: active) 
                padding: 0 0 0 5px;

        /* IE specific styles */
        @supports (-ms-accelerator:true) {
                padding: 0 0 0 5px;
        }  {
            outline: none;
            background: #fff;
            -moz-appearance: window;
            -webkit-appearance: none;
            border-radius: 0px;
            text-overflow: "";
            background-image: url('');
            background-size: auto 6px;
            background-repeat: no-repeat;
            background-position: 96% 13px;
            cursor: pointer;
            height: 30px;
            width: 100%;
            border: 1px solid #9e9e9e;
            padding: 0 15px 0 5px;
            padding-right: 15px\9;      /* This will be apllied only to IE 7, IE 8 and IE 9 as */
            *padding-right: 15px;        /* This will be apllied only to IE 7 and below. */
            _padding-right: 15px;       /* This will be apllied only to IE 6 and below. */

HTML code

    <div class="select-example">
        <select class="my-select-box">
            <option value="1">First Option</option>
            <option value="2">Second Option</option>
            <option value="3">Third Option</option>
            <option value="4">Fourth Option</option>

Android, How to limit width of TextView (and add three dots at the end of text)?

I take it you want to limit width to one line and not limit it by character? Since singleLine is deprecated, you could try using the following together:


jQuery: find element by text

The following jQuery selects div nodes that contain text but have no children, which are the leaf nodes of the DOM tree.

$('div:contains("test"):not(:has(*))').css('background-color', 'red');
<div>This is a test, nested in div1</div>_x000D_
<div>Nested in div1<div>_x000D_
<div>div2 test_x000D_
<div>This is another test, nested in div2</div>_x000D_
<div>Nested in div2</div>_x000D_
<script src=""></script>

Deserializing a JSON file with JavaScriptSerializer()

Assuming you don't want to create another class, you can always let the deserializer give you a dictionary of key-value-pairs, like so:

string s = //{ "user" : {    "id" : 12345,    "screen_name" : "twitpicuser"}};
var serializer = new JavaScriptSerializer();
var result = serializer.DeserializeObject(s);

You'll get back something, where you can do:

var userId = int.Parse(result["user"]["id"]); // or (int)result["user"]["id"] depending on how the JSON is serialized.
// etc.

Look at result in the debugger to see, what's in there.

SVN 405 Method Not Allowed

I just fixed this in my own repository. I'm using TortoiseSVN on Windows, so I'm not sure exactly what commands this translates to on the command line, but here's what I did:

The problematic folder is called lib, and it was due to be added.

  • First I undid the add, so that SVN was no longer paying attention to it.
  • Then I renamed it (to libs, not that that matters) using the Windows context menu, added it, and committed successfully.
  • Finally I renamed it back to lib using TortoiseSVN's context menu (this is probably important), and committed again.

Write string to text file and ensure it always overwrites the existing content.

Generally, FileMode.Create is what you're looking for.

Why is 1/1/1970 the "epoch time"?


The earliest versions of Unix time had a 32-bit integer incrementing at a rate of 60 Hz, which was the rate of the system clock on the hardware of the early Unix systems. The value 60 Hz still appears in some software interfaces as a result. The epoch also differed from the current value. The first edition Unix Programmer's Manual dated November 3, 1971 defines the Unix time as "the time since 00:00:00, Jan. 1, 1971, measured in sixtieths of a second".

how to activate a textbox if I select an other option in drop down box

Below is the core JavaScript you need to write:

<script type="text/javascript">
function CheckColors(val){
 var element=document.getElementById('color');
 if(val=='pick a color'||val=='others')'block';

  <select name="color" onchange='CheckColors(this.value);'> 
    <option>pick a color</option>  
    <option value="red">RED</option>
    <option value="blue">BLUE</option>
    <option value="others">others</option>
<input type="text" name="color" id="color" style='display:none;'/>

Add multiple items to already initialized arraylist in java

What is the "source" of those integer? If it is something that you need to hard code in your source code, you may do


How to zoom div content using jquery?

If you want that image to be zoomed on mouse hover :

$(document).ready( function() {
$('#div img').hover(
    function() {
        $(this).animate({ 'zoom': 1.2 }, 400);
    function() {
        $(this).animate({ 'zoom': 1 }, 400);

?or you may do like this if zoom in and out buttons are used :



function ZoomIn (event) {

    $("#div img").width(
        $("#div img").width() * 1.2

    $("#div img").height(
        $("#div img").height() * 1.2

function  ZoomOut (event) {

    $("#div img").width(
        $("#imgDtls").width() * 0.5

    $("#div img").height(
        $("#div img").height() * 0.5

Angular and debounce

Spent hours on this, hopefully I can save someone else some time. To me the following approach to using debounce on a control is more intuitive and easier to understand for me. It's built on the docs solution for autocomplete but with the ability for me to intercept the calls without having to depend on tying the data to the DOM.


A use case scenario for this might be checking a username after it's typed to see if someone has already taken it, then warning the user.

Note: don't forget, (blur)="function(something.value) might make more sense for you depending on your needs.

jQuery 'each' loop with JSON array

This works for me:

$.get("data.php", function(data){
    var expected = ['justIn', 'recent', 'old'];
    var outString = '';
    $.each(expected, function(i, val){
        var contentArray = data[val];
        outString += '<ul><li><b>' + val + '</b>: ';
        $.each(contentArray, function(i1, val2){
            var textID = val2.textId;
            var text = val2.text;
            var textType = val2.textType;
            outString += '<br />('+textID+') '+'<i>'+text+'</i> '+textType;
        outString += '</li></ul>';
}, 'json');

This produces this output:

<div id="contentHere"><ul>
<br />
(123) <i>Hello</i> Greeting<br>
(514) <i>What's up?</i> Question<br>
(122) <i>Come over here</i> Order</li>
<br />
(1255) <i>Hello</i> Greeting<br>
(6564) <i>What's up?</i> Question<br>
(0192) <i>Come over here</i> Order</li>
<br />
(5213) <i>Hello</i> Greeting<br>
(9758) <i>What's up?</i> Question<br>
(7655) <i>Come over here</i> Order</li>

And looks like this:

  • justIn:
    (123) Hello Greeting
    (514) What's up? Question
    (122) Come over here Order
  • recent:
    (1255) Hello Greeting
    (6564) What's up? Question
    (0192) Come over here Order
  • old:
    (5213) Hello Greeting
    (9758) What's up? Question
    (7655) Come over here Order

Also, remember to set the contentType as 'json'

Session 'app': Error Installing APK

I fixed my issue, simply by using :

Build->Clean Project


Build->Rebuild Project

A method to reverse effect of java String.split()?

Google also provides a joiner class in their Google Collections library:

Joiner API

Google Collections vs onClick

Go for this as it will give you both standard and performance.

      //Some code

As the second method is simple JavaScript code and is faster than jQuery. But here performance will be approximately the same.

How do I activate C++ 11 in CMake?

OS X and Homebrew LLVM related:

Don't forget to call cmake_minimum_required(VERSION 3.3) and project() after it!

Or CMake will insert project() implicitly before line 1, causing trouble with Clang version detection and possibly other sorts of troubles. Here is a related issue.

How to write/update data into cells of existing XLSX workbook using xlsxwriter in python

You can do by xlwings as well

import xlwings as xw
for book in xlwings.books:

unix sort descending order

If you only want to sort only on the 5th field then use -k5,5.

Also, use the -t command line switch to specify the delimiter to tab. Try this:

sort  -k5,5 -r -n -t \t filename

or if the above doesn't work (with the tab) this:

sort  -k5,5 -r -n -t $'\t' filename

The man page for sort states:

-t, --field-separator=SEP use SEP instead of non-blank to blank transition

Finally, this SO question Unix Sort with Tab Delimiter might be helpful.

How to make rounded percentages add up to 100%

Probably the "best" way to do this (quoted since "best" is a subjective term) is to keep a running (non-integral) tally of where you are, and round that value.

Then use that along with the history to work out what value should be used. For example, using the values you gave:

Value      CumulValue  CumulRounded  PrevBaseline  Need
---------  ----------  ------------  ------------  ----
13.626332   13.626332            14             0    14 ( 14 -  0)
47.989636   61.615968            62            14    48 ( 62 - 14)
 9.596008   71.211976            71            62     9 ( 71 - 62)
28.788024  100.000000           100            71    29 (100 - 71)

At each stage, you don't round the number itself. Instead, you round the accumulated value and work out the best integer that reaches that value from the previous baseline - that baseline is the cumulative value (rounded) of the previous row.

This works because you're not losing information at each stage but rather using the information more intelligently. The 'correct' rounded values are in the final column and you can see that they sum to 100.

You can see the difference between this and blindly rounding each value, in the third value above. While 9.596008 would normally round up to 10, the accumulated 71.211976 correctly rounds down to 71 - this means that only 9 is needed to add to the previous baseline of 62.

This also works for "problematic" sequence like three roughly-1/3 values, where one of them should be rounded up:

Value      CumulValue  CumulRounded  PrevBaseline  Need
---------  ----------  ------------  ------------  ----
33.333333   33.333333            33             0    33 ( 33 -  0)
33.333333   66.666666            67            33    34 ( 67 - 33)
33.333333   99.999999           100            67    33 (100 - 67)

HTML5 phone number validation with pattern

This code will accept all country code with + sign

<input type="text" pattern="[0-9]{5}[-][0-9]{7}[-][0-9]{1}"/>

Some countries allow a single "0" character instead of "+" and others a double "0" character instead of the "+". Neither are standard.

error while loading shared libraries:

Your system likely does not provide the ncurses library at the version android studio uses. My arch linux install only had ncurses 6 but android studio needs version 5. You could check if your distribution has a compatability package, or use the solution that Rahmat Aligos suggested.

Can't install nuget package because of "Failed to initialize the PowerShell host"

If the above answers dint work for you -

  1. Open Run - windows + R
  2. Open registry editor - type regedit.exe
  3. Open - HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\PowerShell
  4. In the right pane - Modify "ExecutionPolicy" and keep its "Value Data" as blank.
  5. Restart your visual studio, Now your Powershell can initialize properly.

Adding delay between execution of two following lines

If you're targeting iOS 4.0+, you can do the following:

[executing first operation];
double delayInSeconds = 2.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    [executing second operation];

Clear android application user data

If you want to do manually then You also can clear your user data by clicking “Clear Data” button in Settings–>Applications–>Manage Aplications–> YOUR APPLICATION

or Is there any other way to do that?

Then Download code here

enter image description here

Connect Android Studio with SVN

Go to File->Settings->Version Control->Subversion enter the path for your SVN executable in the General tab under Subversion configuration directory. Also, you can download a latest SVN client such as VisualSVN and point the path to the executable as mentioned above. That will most likely solve your problem.

Get login username in java

Below is a solution for WINDOWS ONLY

In cases where the application (like Tomcat) is started as a windows service, the System.getProperty("") or System.getenv().get("USERNAME") return the user who started the service and not the current logged in user name.

Also in Java 9 the NTSystem etc classes will not be accessible

So workaround for windows: You can use wmic, so you have to run the below command

wmic ComputerSystem get UserName

If available, this will return output of the form:


Note: For windows you need to use cmd /c as a prefix, so below is a crude program as an example:

    Process exec = Runtime.getRuntime().exec("cmd /c wmic ComputerSystem get UserName".split(" "));
    try (BufferedReader bw = new BufferedReader(new InputStreamReader(exec.getInputStream()))) {
        System.out.println(bw.readLine() + "\n" + bw.readLine()+ "\n" + bw.readLine());

Sorting string array in C#

This code snippet is working properly enter image description here

How to close existing connections to a DB

in restore wizard click "close existing connections to destination database"

in Detach Database wizard click "Drop connection" item.


We had the same problem on a CentOS7 machine. Disabling the VERIFYHOST VERIFYPEER did not solve the problem, we did not have the cURL error anymore but the response still was invalid. Doing a wget to the same link as the cURL was doing also resulted in a certificate error.

-> Our solution also was to reboot the VPS, this solved it and we were able to complete the request again.

For us this seemed to be a memory corruption problem. Rebooting the VPS reloaded the libary in the memory again and now it works. So if the above solution from @clover does not work try to reboot your machine.

Get a UTC timestamp

As wizzard pointed out, the correct method is,

new Date().getTime();

or under Javascript 1.5, just;

From the documentation,

The value returned by the getTime method is the number of milliseconds since 1 January 1970 00:00:00 UTC.

If you wanted to make a time stamp without milliseconds you can use,

Math.floor( / 1000);

I wanted to make this an answer so the correct method is more visible.

You can compare ExpExc's and Narendra Yadala's results to the method above at, and verify with or by running date +%s on a Unix terminal.

How to replace deprecated

you must use import;

and use the constructor

public CustomActionBarDrawerToggle(Activity mActivity,DrawerLayout mDrawerLayout)
    super(mActivity, mDrawerLayout, R.string.ns_menu_open, R.string.ns_menu_close);

and if the drawer toggle button becomes dark then you must use the supportActionBar provided in the support library.

You can implement supportActionbar from this link:

How to store a dataframe using Pandas

Numpy file formats are pretty fast for numerical data

I prefer to use numpy files since they're fast and easy to work with. Here's a simple benchmark for saving and loading a dataframe with 1 column of 1million points.

import numpy as np
import pandas as pd

num_dict = {'voltage': np.random.rand(1000000)}
num_df = pd.DataFrame(num_dict)

using ipython's %%timeit magic function

with open('num.npy', 'wb') as np_file:, num_df)

the output is

100 loops, best of 3: 5.97 ms per loop

to load the data back into a dataframe

with open('num.npy', 'rb') as np_file:
    data = np.load(np_file)

data_df = pd.DataFrame(data)

the output is

100 loops, best of 3: 5.12 ms per loop



There's a problem if you save the numpy file using python 2 and then try opening using python 3 (or vice versa).

How to change the URL from "localhost" to something else, on a local system using wampserver?

They are probably using a virtual host (

You can go into your Apache configuration file (httpd.conf) or your virtual host configuration file (recommended) and add something like:

<VirtualHost *:80>
    DocumentRoot /www/ap-mispro
    ServerName ap-mispro

    # Other directives here

And when you call up http://ap-mispro/ you would see whatever is in C:/wamp/www/ap-mispro (assuming default directory structure). The ServerName and DocumentRoot do no have to have the same name at all. Other factors needed to make this work:

  1. You have to make sure httpd-vhosts.conf is included by httpd.conf for your changes in that file to take effect.
  2. When you make changes to either file, you have to restart Apache to see your changes.
  3. You have to change your hosts file for your computer to know where to go when you type http://ap-mispro into your browser. This change to your hosts file will only apply to your computer - not that it sounds like you are trying from anyone else's.

There are plenty more things to know about virtual hosts but this should get you started.

How can I send mail from an iPhone application

A few things I'd like to add here:

  1. Using the mailto URL won't work in the simulator as isn't installed on the simulator. It does work on device though.

  2. There is a limit to the length of the mailto URL. If the URL is larger than 4096 characters, won't launch.

  3. There is a new class in OS 3.0 that lets you send an e-mail without leaving your app. See the class MFMailComposeViewController.

How to save an image locally using Python whose URL address I already know?

Late answer, but for python>=3.6 you can use dload, i.e.:

import dload"")

if you need the image as bytes, use:

img_bytes = dload.bytes("")

install using pip3 install dload

How do you post to the wall on a facebook page (not profile)

You can not post to Facebook walls automatically without creating an application and using the templated feed publisher as Frank pointed out.

The only thing you can do is use the 'share' widgets that they provide, which require user interaction.

Save PHP array to MySQL?

Just use the serialize PHP function:

$myArray = array('1', '2');
$seralizedArray = serialize($myArray);

However, if you are using simple arrays like that you might as well use implode and explode.Use a blank array instead of new.

Foreign Key naming scheme

Try using upper-cased Version 4 UUID with first octet replaced by FK and '_' (underscore) instead of '-' (dash).


  • FK_1786_45A6_A17C_F158C0FB343E
  • FK_45A5_4CFA_84B0_E18906927B53

Rationale is the following

  • Strict generation algorithm => uniform names;
  • Key length is less than 30 characters, which is naming length limitation in Oracle (before 12c);
  • If your entity name changes you don't need to rename your FK like in entity-name based approach (if DB supports table rename operator);
  • One would seldom use foreign key constraint's name. E.g. DB tool usually shows what the constraint applies to. No need to be afraid of cryptic look, because you can avoid using it for "decryption".

What value could I insert into a bit type column?

If you're using SQL Server, you can set the value of bit fields with 0 and 1


'true' and 'false' (yes, using strings)

...your_bit_field='false'... => equivalent to 0

Getting time span between two times in C#?

Two points:

  1. Check your inputs. I can't imagine a situation where you'd get 2 hours by subtracting the time values you're talking about. If I do this:

        DateTime startTime = Convert.ToDateTime("7:00 AM");
        DateTime endtime = Convert.ToDateTime("2:00 PM");
        TimeSpan duration = startTime - endtime;

    ... I get -07:00:00 as the result. And even if I forget to provide the AM/PM value:

        DateTime startTime = Convert.ToDateTime("7:00");
        DateTime endtime = Convert.ToDateTime("2:00");
        TimeSpan duration = startTime - endtime;

    ... I get 05:00:00. So either your inputs don't contain the values you have listed or you are in a machine environment where they are begin parsed in an unexpected way. Or you're not actually getting the results you are reporting.

  2. To find the difference between a start and end time, you need to do endTime - startTime, not the other way around.

Where is the Query Analyzer in SQL Server Management Studio 2008 R2?

Yes there is one and it is inside the SQLServer management studio. Unlike the previous versions I think. Follow these simple steps.

1)Right click on a database in the Object explorer 2)Selected New Query from the popup menu 3)Query Analyzer will be opened.

Enjoy work.

Link to "pin it" on pinterest without generating a button

I Found some code for wordpress:

 <script type="text/javascript">

    function insert_pinterest($content) {
        global $post;
        $posturl = urlencode(get_permalink()); //Get the post URL
        $pinspan = '<span class="pinterest-button">';
     $pinurl = '';
     $pinend = '</span>';
        $pattern = '//i';
        $replacement = $pinspan.$pinurl.'$2.$3'.$pindescription.$pinfinish.''.$pinend;
        $content = preg_replace( $pattern, $replacement, $content );
        //Fix the link problem
        $newpattern = '/<span class="pinterest-button"><\/a><\/span><\/a>/i';
     $replacement = '';
     $content = preg_replace( $newpattern, $replacement, $content );
     return $content;
    add_filter( 'the_content', 'insert_pinterest' );


Then you put the following in your PHP:

<?php $pinterestimage = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' ); ?>
<a href="<?php echo urlencode(get_permalink($post->ID)); ?>&media=<?php echo $pinterestimage[0]; ?>&description=<?php the_title(); ?>">Pin It</a>

How to implement a Map with multiple keys?

I recommend something like this:

    public class MyMap {

      Map<Object, V> map = new HashMap<Object, V>();

      public V put(K1 key,V value){
        return map.put(key, value);

      public V put(K2 key,V value){
        return map.put(key, value);

      public V get(K1 key){    
        return map.get(key);

      public V get(K2 key){    
        return map.get(key);

      //Same for conatains


Then you can use it like:
myMap.put(k1,value) or myMap.put(k2,value)

Advantages: It is simple, enforces type safety, and doesn't store repeated data (as the two maps solutions do, though still store duplicate values).
Drawbacks: Not generic.

How to do a scatter plot with empty circles in Python?

So I assume you want to highlight some points that fit a certain criteria. You can use Prelude's command to do a second scatter plot of the hightlighted points with an empty circle and a first call to plot all the points. Make sure the s paramter is sufficiently small for the larger empty circles to enclose the smaller filled ones.

The other option is to not use scatter and draw the patches individually using the circle/ellipse command. These are in matplotlib.patches, here is some sample code on how to draw circles rectangles etc.

What is the difference between git clone and checkout?

git clone is to fetch your repositories from the remote git server.

git checkout is to checkout your desired status of your repository (like branches or particular files).

E.g., you are currently on master branch and you want to switch into develop branch.

git checkout develop_branch

E.g., you want to checkout to a particular status of a particular file

git checkout commit_point_A -- <filename>

Here is a good reference for you to learn Git, lets you understand much more easily.

How to get the number of columns in a matrix?

When want to get row size with size() function, below code can be used:


Another usage for it:

[height, width] = size(A)

So, you can get 2 dimension of your matrix.

UILabel Align Text to center

N.B.: As per the UILabel class reference, as of iOS 6 this approach is now deprecated.

Simply use the textAlignment property to see the required alignment using one of the UITextAlignment values. (UITextAlignmentLeft, UITextAlignmentCenter or UITextAlignmentRight.)

e.g.: [myUILabel setTextAlignment:UITextAlignmentCenter];

See the UILabel Class Reference for more information.

How can I exclude multiple folders using Get-ChildItem -exclude?

I wanted a solution that didn't involve looping over every single item and doing ifs. Here's a solution that is just a simple recursive function over Get-ChildItem. We just loop and recurse over directories.

function Get-RecurseItem {
    param (
        [string[]]$Exclude = @(),
        [string]$Include = '*'
    Get-ChildItem -Path (Join-Path $Path '*') -Exclude $Exclude -Directory | ForEach-Object {
        @(Get-ChildItem -Path (Join-Path $_ '*') -Include $Include -Exclude $Exclude -File) + ``
        @(Get-RecurseItem -Path $_ -Include $Include -Exclude $Exclude)

What does 'const static' mean in C and C++?

It has uses in both C and C++.

As you guessed, the static part limits its scope to that compilation unit. It also provides for static initialization. const just tells the compiler to not let anybody modify it. This variable is either put in the data or bss segment depending on the architecture, and might be in memory marked read-only.

All that is how C treats these variables (or how C++ treats namespace variables). In C++, a member marked static is shared by all instances of a given class. Whether it's private or not doesn't affect the fact that one variable is shared by multiple instances. Having const on there will warn you if any code would try to modify that.

If it was strictly private, then each instance of the class would get its own version (optimizer notwithstanding).

Illegal string offset Warning PHP

Please try this way.... I have tested this code.... It works....

$memcachedConfig = array("host" => "","port" => "11211");

Adding a Scrollable JTextArea (Java)

A scroll pane is a container which contains another component. You can't add your text area to two different scroll panes. The scroll pane takes care of the horizontal and vertical scroll bars.

And if you never add the scroll pane to the frame, it will never be visible.

Read the swing tutorial about scroll panes.

Seeing if data is normally distributed in R

when you perform a test, you ever have the probabilty to reject the null hypothesis when it is true.

See the nextt R code:



The graph shows that whether you have a sample size small or big a 5% of the times you have a chance to reject the null hypothesis when it s true (a Type-I error)

How to convert integer to char in C?

To convert integer to char only 0 to 9 will be converted. As we know 0's ASCII value is 48 so we have to add its value to the integer value to convert in into the desired character hence

int i=5;
char c = i+'0';

Executors.newCachedThreadPool() versus Executors.newFixedThreadPool()

The ThreadPoolExecutor class is the base implementation for the executors that are returned from many of the Executors factory methods. So let's approach Fixed and Cached thread pools from ThreadPoolExecutor's perspective.


The main constructor of this class looks like this:

public ThreadPoolExecutor(
                  int corePoolSize,
                  int maximumPoolSize,
                  long keepAliveTime,
                  TimeUnit unit,
                  BlockingQueue<Runnable> workQueue,
                  ThreadFactory threadFactory,
                  RejectedExecutionHandler handler

Core Pool Size

The corePoolSize determines the minimum size of the target thread pool. The implementation would maintain a pool of that size even if there are no tasks to execute.

Maximum Pool Size

The maximumPoolSize is the maximum number of threads that can be active at once.

After the thread pool grows and becomes bigger than the corePoolSize threshold, the executor can terminate idle threads and reach to the corePoolSize again. If allowCoreThreadTimeOut is true, then the executor can even terminate core pool threads if they were idle more than keepAliveTime threshold.

So the bottom line is if threads remain idle more than keepAliveTime threshold, they may get terminated since there is no demand for them.


What happens when a new task comes in and all core threads are occupied? The new tasks will be queued inside that BlockingQueue<Runnable> instance. When a thread becomes free, one of those queued tasks can be processed.

There are different implementations of the BlockingQueue interface in Java, so we can implement different queuing approaches like:

  1. Bounded Queue: New tasks would be queued inside a bounded task queue.

  2. Unbounded Queue: New tasks would be queued inside an unbounded task queue. So this queue can grow as much as the heap size allows.

  3. Synchronous Handoff: We can also use the SynchronousQueue to queue the new tasks. In that case, when queuing a new task, another thread must already be waiting for that task.

Work Submission

Here's how the ThreadPoolExecutor executes a new task:

  1. If fewer than corePoolSize threads are running, tries to start a new thread with the given task as its first job.
  2. Otherwise, it tries to enqueue the new task using the BlockingQueue#offer method. The offer method won't block if the queue is full and immediately returns false.
  3. If it fails to queue the new task (i.e. offer returns false), then it tries to add a new thread to the thread pool with this task as its first job.
  4. If it fails to add the new thread, then the executor is either shut down or saturated. Either way, the new task would be rejected using the provided RejectedExecutionHandler.

The main difference between the fixed and cached thread pools boils down to these three factors:

  1. Core Pool Size
  2. Maximum Pool Size
  3. Queuing

| Pool Type | Core Size |    Maximum Size   |         Queuing Strategy        |
|   Fixed   | n (fixed) |     n (fixed)     | Unbounded `LinkedBlockingQueue` |
|   Cached  |     0     | Integer.MAX_VALUE |        `SynchronousQueue`       |

Fixed Thread Pool

Here's how the Excutors.newFixedThreadPool(n) works:

public static ExecutorService newFixedThreadPool(int nThreads) {
    return new ThreadPoolExecutor(nThreads, nThreads,
                                  0L, TimeUnit.MILLISECONDS,
                                  new LinkedBlockingQueue<Runnable>());

As you can see:

  • The thread pool size is fixed.
  • If there is high demand, it won't grow.
  • If threads are idle for quite some time, it won't shrink.
  • Suppose all those threads are occupied with some long-running tasks and the arrival rate is still pretty high. Since the executor is using an unbounded queue, it may consume a huge part of the heap. Being unfortunate enough, we may experience an OutOfMemoryError.

When should I use one or the other? Which strategy is better in terms of resource utilization?

A fixed-size thread pool seems to be a good candidate when we're going to limit the number of concurrent tasks for resource management purposes.

For example, if we're going to use an executor to handle web server requests, a fixed executor can handle the request bursts more reasonably.

For even better resource management, it's highly recommended to create a custom ThreadPoolExecutor with a bounded BlockingQueue<T> implementation coupled with reasonable RejectedExecutionHandler.

Cached Thread Pool

Here's how the Executors.newCachedThreadPool() works:

public static ExecutorService newCachedThreadPool() {
    return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                  60L, TimeUnit.SECONDS,
                                  new SynchronousQueue<Runnable>());

As you can see:

  • The thread pool can grow from zero threads to Integer.MAX_VALUE. Practically, the thread pool is unbounded.
  • If any thread is idle for more than 1 minute, it may get terminated. So the pool can shrink if threads remain too much idle.
  • If all allocated threads are occupied while a new task comes in, then it creates a new thread, as offering a new task to a SynchronousQueue always fails when there is no one on the other end to accept it!

When should I use one or the other? Which strategy is better in terms of resource utilization?

Use it when you have a lot of predictable short-running tasks.

Dealing with nginx 400 "The plain HTTP request was sent to HTTPS port" error

The above answers are incorrect in that most over-ride the 'is this connection HTTPS' test to allow serving the pages over http irrespective of connection security.

The secure answer using an error-page on an NGINX specific http 4xx error code to redirect the client to retry the same request to https. (as outlined here )

The OP should use:

server {
  listen        12345;

  root         /var/www/php;

  ssl           on;

  # If they come here using HTTP, bounce them to the correct scheme
  error_page 497 https://$server_name:$server_port$request_uri;


How to fill DataTable with SQL Table

The answers above are correct, but I thought I would expand another answer by offering a way to do the same if you require to pass parameters into the query.

The SqlDataAdapter is quick and simple, but only works if you're filling a table with a static request ie: a simple SELECT without parameters.

Here is my way to do the same, but using a parameter to control the data I require in my table. And I use it to populate a DropDownList.

//populate the Programs dropdownlist according to the student's study year / preference
DropDownList ddlPrograms = (DropDownList)DetailsView1.FindControl("ddlPrograms");
if (ddlPrograms != null)
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["ATCNTV1ConnectionString"].ConnectionString))
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = "SELECT ProgramID, ProgramName FROM tblPrograms WHERE ProgramCatID > 0 AND ProgramStatusID = (CASE WHEN @StudyYearID = 'VPR' THEN 10 ELSE 7 END) AND ProgramID NOT IN (23,112,113) ORDER BY ProgramName";
            cmd.Parameters.Add("@StudyYearID", SqlDbType.Char).Value = "11";
            DataTable wsPrograms = new DataTable();

            //populate the Programs ddl list
            ddlPrograms.DataSource = wsPrograms;
            ddlPrograms.DataTextField = "ProgramName";
            ddlPrograms.DataValueField = "ProgramID";
            ddlPrograms.Items.Insert(0, new ListItem("<Select Program>", "0"));
        catch (Exception ex)
            // Handle the error


How to get PID of process by specifying process name and store it in a variable to use further?

pids=$(pgrep <name>)

will get you the pids of all processes with the given name. To kill them all, use

kill -9 $pids

To refrain from using a variable and directly kill all processes with a given name issue

pkill -9 <name>

Errno 10061 : No connection could be made because the target machine actively refused it ( client - server )

instead of localhost of '', use local network address as host in case of both - the server and the client - code.

host = '' port = 12345

use this host address when binding and connecting to the socket.

server.bind((host, port)) client.connect((host, port))

this change solved the issue for me.

Warning: Attempt to present * on * whose view is not in the window hierarchy - swift

Rather than finding top view controller, one can use

viewController.modalPresentationStyle = UIModalPresentationStyle.currentContext

Where viewController is the controller which you want to present This is useful when there are different kinds of views in hierarchy like TabBar, NavBar, though others seems to be correct but more sort of hackish

The other presentation style can be found on apple doc

Is there a function to split a string in PL/SQL?

There is a simple way folks. Use REPLACE function. Here is an example of comma separated string ready to be passed to IN clause.


StatusString :=   REPLACE('Active,Completed', ',', ''',''');

In SQL Plus:

Select  REPLACE('Active,Completed', ',', ''',''') from dual;

Access Form - Syntax error (missing operator) in query expression

Try making the field names legal by removing spaces. It's a long shot but it has actually helped me before.

javascript: Disable Text Select

For JavaScript use this function:

function disableselect(e) {return false}
document.onselectstart = new Function (return false)
document.onmousedown = disableselect

to enable the selection use this:

function reEnable() {return true}

and use this function anywhere you want:

document.onclick = reEnable

What does this format means T00:00:00.000Z?

Please use DateTimeFormatter ISO_DATE_TIME = DateTimeFormatter.ISO_DATE_TIME; instead of DateTimeFormatter.ofPattern("dd-MM-yyyy HH:mm:ss") or any pattern

This fixed my problem Below

java.time.format.DateTimeParseException: Text '2019-12-18T19:00:00.000Z' could not be parsed at index 10

How to SHUTDOWN Tomcat in Ubuntu?

if you have yout tomcat installed you can do :

sh path2tomcat/bin/

How to count lines of Java code using IntelliJ IDEA?

Statistic plugins works fine!

Here is a quick case:

  1. Ctrl+Shift+A and serach for "Statistic" to open the panel.
  2. You will see panel as the screenshot and then click Refresh for whole project or select your project or file and Refresh on selection for only selection.


How to send a POST request with BODY in swift

I've slightly edited SwiftDeveloper's answer, because it wasn't working for me. I added Alamofire validation as well.

let body: NSMutableDictionary? = [
    "name": "\(nameLabel.text!)",
    "phone": "\(phoneLabel.text!))"]

let url = NSURL(string: "" as String)
var request = URLRequest(url: url! as URL)
request.httpMethod = "POST"
request.setValue("application/json", forHTTPHeaderField: "Content-Type")
let data = try! body!, options: JSONSerialization.WritingOptions.prettyPrinted)

let json = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
if let json = json {
request.httpBody = json!.data(using: String.Encoding.utf8.rawValue)
let alamoRequest = Alamofire.request(request as URLRequestConvertible)
alamoRequest.validate(statusCode: 200..<300)
alamoRequest.responseString { response in

    switch response.result {
        case .success:
        case .failure(let error):

Copying and pasting data using VBA code

'So from this discussion i am thinking this should be the code then.

Sub Button1_Click()
    Dim excel As excel.Application
    Dim wb As excel.Workbook
    Dim sht As excel.Worksheet
    Dim f As Object

    Set f = Application.FileDialog(3)
    f.AllowMultiSelect = False

    Set excel = CreateObject("excel.Application")
    Set wb = excel.Workbooks.Open(f.SelectedItems(1))
    Set sht = wb.Worksheets("Data")

    Range("A1").PasteSpecial Paste:=xlPasteValues

End Sub

'Let me know if this is correct or a step was missed. Thx.

Failed to install *.apk on device 'emulator-5554': EOF

Try window->show view->devices->view menu->Reset adb and again run application.

Send a SMS via intent

Uri uri = Uri.parse("smsto:YOUR_SMS_NUMBER");   
Intent intent = new Intent(Intent.ACTION_SENDTO, uri);   
intent.putExtra("sms_body", "The SMS text");   

Get Max value from List<myType>

var maxAge = list.Max(x => x.Age);

How to replace spaces in file names using a bash script

bash 4.0

shopt -s globstar
for file in **/*\ *
    mv "$file" "${file// /_}"       

What exactly does Double mean in java?

A double is an IEEE754 double-precision floating point number, similar to a float but with a larger range and precision.

IEEE754 single precision numbers have 32 bits (1 sign, 8 exponent and 23 mantissa bits) while double precision numbers have 64 bits (1 sign, 11 exponent and 52 mantissa bits).

A Double in Java is the class version of the double basic type - you can use doubles but, if you want to do something with them that requires them to be an object (such as put them in a collection), you'll need to box them up in a Double object.

Use Robocopy to copy only changed files?

Looks like /e option is what you need, it'll skip same files/directories.

robocopy c:\data c:\backup /e

If you run the command twice, you'll see the second round is much faster since it skips a lot of things.

Store select query's output in one array in postgres

There are two ways. One is to aggregate:

SELECT array_agg(column_name::TEXT)
FROM information.schema.columns
WHERE table_name = 'aean'

The other is to use an array constructor:

SELECT column_name 
FROM information.schema.columns 
WHERE table_name = 'aean')

I'm presuming this is for plpgsql. In that case you can assign it like this:

colnames := ARRAY(
SELECT column_name
FROM information.schema.columns
WHERE table_name='aean'

POST request send json data java HttpUrlConnection

I had a similar issue, I was getting 400, Bad Request only with the PUT, where as POST request was perfectly fine.

Below code worked fine for POST but was giving BAD Request for PUT:

conn.setRequestProperty("Content-Type", "application/json");

After making below changes worked fine for both POST and PUT

conn.setRequestProperty("Content-Type", "application/json; charset=UTF-8");

How do I get the path to the current script with Node.js?

Every Node.js program has some global variables in its environment, which represents some information about your process and one of it is __dirname.

sed edit file in place

You didn't specify what shell you are using, but with zsh you could use the =( ) construct to achieve this. Something along the lines of:

cp =(sed ... file; sync) file

=( ) is similar to >( ) but creates a temporary file which is automatically deleted when cp terminates.

HTTP 400 (bad request) for logical error, not malformed request syntax

Status 422 (RFC 4918, Section 11.2) comes to mind:

The 422 (Unprocessable Entity) status code means the server understands the content type of the request entity (hence a 415(Unsupported Media Type) status code is inappropriate), and the syntax of the request entity is correct (thus a 400 (Bad Request) status code is inappropriate) but was unable to process the contained instructions. For example, this error condition may occur if an XML request body contains well-formed (i.e., syntactically correct), but semantically erroneous, XML instructions.