Programs & Examples On #Magic constants

How to use fetch in typescript

Actually, pretty much anywhere in typescript, passing a value to a function with a specified type will work as desired as long as the type being passed is compatible.

That being said, the following works...

      .then(res => res.json())
      .then((res: Actor) => {
          // res is now an Actor

I wanted to wrap all of my http calls in a reusable class - which means I needed some way for the client to process the response in its desired form. To support this, I accept a callback lambda as a parameter to my wrapper method. The lambda declaration accepts an any type as shown here...

callBack: (response: any) => void

But in use the caller can pass a lambda that specifies the desired return type. I modified my code from above like this...

  .then(res => res.json())
  .then(res => {
      if (callback) {
        callback(res);    // Client receives the response as desired type.  

So that a client can call it with a callback like...

(response: IApigeeResponse) => {
    // Process response as an IApigeeResponse

Passing javascript variable to html textbox

You could also use to localStorage feature of HTML5 to store your test value and then access it at any other point in your website by using the localStorage.getItem() method. To see how this works you should look at the w3schools explanation or the explanation from the Opera Developer website. Hope this helps.

How to determine day of week by passing specific date?

One line answer:

return LocalDate.parse("06/02/2018",DateTimeFormatter.ofPattern("dd/MM/yyyy")).getDayOfWeek().name();

Usage Example:

public static String getDayOfWeek(String date){
  return LocalDate.parse(date, DateTimeFormatter.ofPattern("dd/MM/yyyy")).getDayOfWeek().name();

public static void callerMethod(){
   System.out.println(getDayOfWeek("06/02/2018")); //TUESDAY

Initialization of all elements of an array to one default value in C++?

Using std::array, we can do this in a fairly straightforward way in C++14. It is possible to do in C++11 only, but slightly more complicated.

Our interface is a compile-time size and a default value.

template<typename T>
constexpr auto make_array_n(std::integral_constant<std::size_t, 0>, T &&) {
    return std::array<std::decay_t<T>, 0>{};

template<std::size_t size, typename T>
constexpr auto make_array_n(std::integral_constant<std::size_t, size>, T && value) {
    return detail::make_array_n_impl<size>(std::forward<T>(value), std::make_index_sequence<size - 1>{});

template<std::size_t size, typename T>
constexpr auto make_array_n(T && value) {
    return make_array_n(std::integral_constant<std::size_t, size>{}, std::forward<T>(value));

The third function is mainly for convenience, so the user does not have to construct a std::integral_constant<std::size_t, size> themselves, as that is a pretty wordy construction. The real work is done by one of the first two functions.

The first overload is pretty straightforward: It constructs a std::array of size 0. There is no copying necessary, we just construct it.

The second overload is a little trickier. It forwards along the value it got as the source, and it also constructs an instance of make_index_sequence and just calls some other implementation function. What does that function look like?

namespace detail {

template<std::size_t size, typename T, std::size_t... indexes>
constexpr auto make_array_n_impl(T && value, std::index_sequence<indexes...>) {
    // Use the comma operator to expand the variadic pack
    // Move the last element in if possible. Order of evaluation is well-defined
    // for aggregate initialization, so there is no risk of copy-after-move
    return std::array<std::decay_t<T>, size>{ (static_cast<void>(indexes), value)..., std::forward<T>(value) };

}   // namespace detail

This constructs the first size - 1 arguments by copying the value we passed in. Here, we use our variadic parameter pack indexes just as something to expand. There are size - 1 entries in that pack (as we specified in the construction of make_index_sequence), and they have values of 0, 1, 2, 3, ..., size - 2. However, we do not care about the values (so we cast it to void, to silence any compiler warnings). Parameter pack expansion expands out our code to something like this (assuming size == 4):

return std::array<std::decay_t<T>, 4>{ (static_cast<void>(0), value), (static_cast<void>(1), value), (static_cast<void>(2), value), std::forward<T>(value) };

We use those parentheses to ensure that the variadic pack expansion ... expands what we want, and also to ensure we are using the comma operator. Without the parentheses, it would look like we are passing a bunch of arguments to our array initialization, but really, we are evaluating the index, casting it to void, ignoring that void result, and then returning value, which is copied into the array.

The final argument, the one we call std::forward on, is a minor optimization. If someone passes in a temporary std::string and says "make an array of 5 of these", we would like to have 4 copies and 1 move, instead of 5 copies. The std::forward ensures that we do this.

The full code, including headers and some unit tests:

#include <array>
#include <type_traits>
#include <utility>

namespace detail {

template<std::size_t size, typename T, std::size_t... indexes>
constexpr auto make_array_n_impl(T && value, std::index_sequence<indexes...>) {
    // Use the comma operator to expand the variadic pack
    // Move the last element in if possible. Order of evaluation is well-defined
    // for aggregate initialization, so there is no risk of copy-after-move
    return std::array<std::decay_t<T>, size>{ (static_cast<void>(indexes), value)..., std::forward<T>(value) };

}   // namespace detail

template<typename T>
constexpr auto make_array_n(std::integral_constant<std::size_t, 0>, T &&) {
    return std::array<std::decay_t<T>, 0>{};

template<std::size_t size, typename T>
constexpr auto make_array_n(std::integral_constant<std::size_t, size>, T && value) {
    return detail::make_array_n_impl<size>(std::forward<T>(value), std::make_index_sequence<size - 1>{});

template<std::size_t size, typename T>
constexpr auto make_array_n(T && value) {
    return make_array_n(std::integral_constant<std::size_t, size>{}, std::forward<T>(value));

struct non_copyable {
    constexpr non_copyable() = default;
    constexpr non_copyable(non_copyable const &) = delete;
    constexpr non_copyable(non_copyable &&) = default;

int main() {
    constexpr auto array_n = make_array_n<6>(5);
    static_assert(std::is_same<std::decay_t<decltype(array_n)>::value_type, int>::value, "Incorrect type from make_array_n.");
    static_assert(array_n.size() == 6, "Incorrect size from make_array_n.");
    static_assert(array_n[3] == 5, "Incorrect values from make_array_n.");

    constexpr auto array_non_copyable = make_array_n<1>(non_copyable{});
    static_assert(array_non_copyable.size() == 1, "Incorrect array size of 1 for move-only types.");

    constexpr auto array_empty = make_array_n<0>(2);
    static_assert(array_empty.empty(), "Incorrect array size for empty array.");

    constexpr auto array_non_copyable_empty = make_array_n<0>(non_copyable{});
    static_assert(array_non_copyable_empty.empty(), "Incorrect array size for empty array of move-only.");

Iterate through string array in Java

String[] elements = { "a", "a","a","a" };

for( int i=0; i<elements.length-1; i++)
    String s1 = elements[i];
    String s2 = elements[i+1];

Make Iframe to fit 100% of container's remaining height

I used display:table to fix a similar issue. It almost works for this, leaving a small vertical scroll bar. If you're trying to populate that flexible column with something other than an iframe it works fine (not

Take the following HTML

  <div class="outer">
    <div class="banner">Banner</div>
    <div class="iframe-container">
      <iframe src="http: //" style="width:100%; height:100%;border:0;"></iframe>

Change the outer div to use display:table and ensure it has a width and height set.

.outer {
  display: table;
  height: 100%;
  width: 100%;

Make the banner a table-row and set its height to whatever your preference is:

.banner {
  display: table-row;
  height: 30px;
  background: #eee;

Add an extra div around your iframe (or whatever content you need) and make it a table-row with height set to 100% (setting its height is critical if you want to embed an iframe to fill the height)

.iframe-container {
  display: table-row;
  height: 100%;

Below is a jsfiddle showing it at work (without an iframe because that doesn't seem to work in the fiddle)

Java: How to read a text file

read the file and then do whatever you want java8 Files.lines(Paths.get("c://lines.txt")).collect(Collectors.toList());

Change visibility of ASP.NET label with JavaScript

You need to be wary of XSS when doing stuff like this:

document.getElementById('<%= Label1.ClientID %>').style.display

The chances are that no-one will be able to tamper with the ClientID of Label1 in this instance, but just to be on the safe side you might want pass it's value through one of the AntiXss library's methods:

document.getElementById('<%= AntiXss.JavaScriptEncode(Label1.ClientID) %>').style.display

What is the purpose and use of **kwargs?

Keyword Arguments are often shortened to kwargs in Python. In computer programming,

keyword arguments refer to a computer language's support for function calls that clearly state the name of each parameter within the function call.

The usage of the two asterisk before the parameter name, **kwargs, is when one doesn't know how many keyword arguments will be passed into the function. When that's the case, it's called Arbitrary / Wildcard Keyword Arguments.

One example of this is Django's receiver functions.

def my_callback(sender, **kwargs):
    print("Request finished!")

Notice that the function takes a sender argument, along with wildcard keyword arguments (**kwargs); all signal handlers must take these arguments. All signals send keyword arguments, and may change those keyword arguments at any time. In the case of request_finished, it’s documented as sending no arguments, which means we might be tempted to write our signal handling as my_callback(sender).

This would be wrong – in fact, Django will throw an error if you do so. That’s because at any point arguments could get added to the signal and your receiver must be able to handle those new arguments.

Note that it doesn't have to be called kwargs, but it needs to have ** (the name kwargs is a convention).

NameError: name 'reduce' is not defined in Python

Or if you use the six library

from six.moves import reduce

How to use && in EL boolean expressions in Facelets?

Facelets is a XML based view technology. The & is a special character in XML representing the start of an entity like &amp; which ends with the ; character. You'd need to either escape it, which is ugly:

rendered="#{beanA.prompt == true &amp;&amp; beanB.currentBase != null}"

or to use the and keyword instead, which is preferred as to readability and maintainability:

rendered="#{beanA.prompt == true and beanB.currentBase != null}"

See also:

Unrelated to the concrete problem, comparing booleans with booleans makes little sense when the expression expects a boolean outcome already. I'd get rid of == true:

rendered="#{beanA.prompt and beanB.currentBase != null}"

javascript compare strings without being case sensitive

You can also use string.match().

var string1 = "aBc";
var match = string1.match(/AbC/i);

if(match) {

How to convert a PIL Image into a numpy array?

I am using Pillow 4.1.1 (the successor of PIL) in Python 3.5. The conversion between Pillow and numpy is straightforward.

from PIL import Image
import numpy as np
im ='1.jpg')
im2arr = np.array(im) # im2arr.shape: height x width x channel
arr2im = Image.fromarray(im2arr)

One thing that needs noticing is that Pillow-style im is column-major while numpy-style im2arr is row-major. However, the function Image.fromarray already takes this into consideration. That is, arr2im.size == im.size and arr2im.mode == im.mode in the above example.

We should take care of the HxWxC data format when processing the transformed numpy arrays, e.g. do the transform im2arr = np.rollaxis(im2arr, 2, 0) or im2arr = np.transpose(im2arr, (2, 0, 1)) into CxHxW format.

Find unique rows in numpy.array

I didn’t like any of these answers because none handle floating-point arrays in a linear algebra or vector space sense, where two rows being “equal” means “within some ”. The one answer that has a tolerance threshold,, took the threshold to be both element-wise and decimal precision, which works for some cases but isn’t as mathematically general as a true vector distance.

Here’s my version:

from scipy.spatial.distance import squareform, pdist

def uniqueRows(arr, thresh=0.0, metric='euclidean'):
    "Returns subset of rows that are unique, in terms of Euclidean distance"
    distances = squareform(pdist(arr, metric=metric))
    idxset = {tuple(np.nonzero(v)[0]) for v in distances <= thresh}
    return arr[[x[0] for x in idxset]]

# With this, unique columns are super-easy:
def uniqueColumns(arr, *args, **kwargs):
    return uniqueRows(arr.T, *args, **kwargs)

The public-domain function above uses scipy.spatial.distance.pdist to find the Euclidean (customizable) distance between each pair of rows. Then it compares each each distance to a threshold to find the rows that are within thresh of each other, and returns just one row from each thresh-cluster.

As hinted, the distance metric needn’t be Euclidean—pdist can compute sundry distances including cityblock (Manhattan-norm) and cosine (the angle between vectors).

If thresh=0 (the default), then rows have to be bit-exact to be considered “unique”. Other good values for thresh use scaled machine-precision, i.e., thresh=np.spacing(1)*1e3.

Cannot get OpenCV to compile because of undefined references?

if anyone still having this problem. One solution is to rebuild the source OpenCV library using MinGW and not use the binaries given by OpenCV. I did it and it worked like a charm.

How to count occurrences of a column value efficiently in SQL?

select, s.age, c.count
from students s
inner join (
    select age, count(*) as count
    from students
    group by age
) c on s.age = c.age
order by id

How to generate gcc debug symbol outside the build target?

Compile with debug information:

gcc -g -o main main.c

Separate the debug information:

objcopy --only-keep-debug main main.debug


cp main main.debug
strip --only-keep-debug main.debug

Strip debug information from origin file:

objcopy --strip-debug main


strip --strip-debug --strip-unneeded main

debug by debuglink mode:

objcopy --add-gnu-debuglink main.debug main
gdb main

You can also use exec file and symbol file separatly:

gdb -s main.debug -e main


(gdb) exec-file main
(gdb) symbol-file main.debug

For details:

(gdb) help exec-file
(gdb) help symbol-file


Changing three.js background to transparent or other color

In 2020 using r115 it works very good with this:

const renderer = new THREE.WebGLRenderer({ alpha: true }); const scene = new THREE.Scene(); scene.background = null;

Remove an item from array using UnderscoreJS

Please exercise care if you are filtering strings and looking for case insensitive filters. _.without() is case sensitive. You can also use _.reject() as shown below.

var arr = ["test","test1","test2"];

var filtered = _.filter(arr, function(arrItem) {
    return arrItem.toLowerCase() !== "TEST".toLowerCase();
// ["test1", "test2"]

var filtered1 = _.without(arr,"TEST");
// ["test", "test1", "test2"]

var filtered2 = _.reject(arr, function(arrItem){ 
    return arrItem.toLowerCase() === "TEST".toLowerCase();
// ["test1", "test2"]

Enable binary mode while restoring a Database from an SQL dump

Your File should be only .sql extension, (.zip, .gz .rar) etc will not support. example: dump.sql

MySQL - Operand should contain 1 column(s)

In my case, the problem was that I sorrounded my columns selection with parenthesis by mistake:

SELECT (p.column1, p.colum2, p.column3) FROM table1 p where p.column1 = 1;

And has to be:

SELECT p.column1, p.colum2, p.column3 FROM table1 p where p.column1 = 1;

Sounds silly, but it was causing this error and it took some time to figure it out.

How to send authorization header with axios

You can try this.

    {headers: {
            "Access-Control-Allow-Origin" : "*",
            "Content-type": "Application/json",
            "Authorization": `Bearer ${your-token}`
  .then((response) => {
      var response =;
    (error) => {
      var status = error.response.status

iPhone 5 CSS media query

Another useful media feature is device-aspect-ratio.

Note that the iPhone 5 does not have a 16:9 aspect ratio. It is in fact 40:71.

iPhone < 5:
@media screen and (device-aspect-ratio: 2/3) {}

iPhone 5:
@media screen and (device-aspect-ratio: 40/71) {}

iPhone 6:
@media screen and (device-aspect-ratio: 375/667) {}

iPhone 6 Plus:
@media screen and (device-aspect-ratio: 16/9) {}

@media screen and (device-aspect-ratio: 3/4) {}

Media Queries @ W3C
iPhone Model Comparison
Aspect Ratio Calculator

Hide div element when screen size is smaller than a specific size

if you are using bootstrap u can just use the hidden-sm ( lg or md or xs) depending on what u want. u can then go into the css file and specify the percentages u want it to show on. in the sample below it will be hiding on large screens, medium ones and extra small ones but show on small screens by taking half of the screen.

<div class="col-sm-12 hidden-lg hidden-md hidden-xs">what ever you want</div>

How can I break from a try/catch block without throwing an exception in Java

This is the code I usually do:

    throw null;//this line just works like a 'break'
  catch (NullReferenceException)
  catch (System.Exception ex)

Create folder with batch but only if it doesn't already exist

set myDIR=LOG
IF not exist %myDIR% (mkdir %myDIR%)

How to get host name with port from a http or https request

You can use HttpServletRequest.getScheme() to retrieve either "http" or "https".

Using it along with HttpServletRequest.getServerName() should be enough to rebuild the portion of the URL you need.

You don't need to explicitly put the port in the URL if you're using the standard ones (80 for http and 443 for https).

Edit: If your servlet container is behind a reverse proxy or load balancer that terminates the SSL, it's a bit trickier because the requests are forwarded to the servlet container as plain http. You have a few options:

1) Use HttpServletRequest.getHeader("x-forwarded-proto") instead; this only works if your load balancer sets the header correctly (Apache should afaik).

2) Configure a RemoteIpValve in JBoss/Tomcat that will make getScheme() work as expected. Again, this will only work if the load balancer sets the correct headers.

3) If the above don't work, you could configure two different connectors in Tomcat/JBoss, one for http and one for https, as described in this article.

How to change MySQL data directory?

Under SuSE 13.1, this works fine to move the mysql data directory elsewhere, e.g. to /home/example_user/ , and to give it a more informative name:

In /var/lib/ :

# mv -T mysql /home/example_user/mysql_datadir
# ln -s /home/example_user/mysql_datadir ./mysql

I restarted mysql:

# systemctl restart mysql.service

but suspect that even that wasn't necessary.

Django Rest Framework File Upload

I'd like to write another option that I feel is cleaner and easier to maintain. We'll be using the defaultRouter to add CRUD urls for our viewset and we'll add one more fixed url specifying the uploader view within the same viewset.


from rest_framework import viewsets, serializers
from rest_framework.decorators import action, parser_classes
from rest_framework.parsers import JSONParser, MultiPartParser
from rest_framework.response import Response
from rest_framework_csv.parsers import CSVParser
from posts.models import Post
from posts.serializers import PostSerializer     

class PostsViewSet(viewsets.ModelViewSet):

    queryset = Post.objects.all()
    serializer_class = PostSerializer 
    parser_classes = (JSONParser, MultiPartParser, CSVParser)

    @action(detail=False, methods=['put'], name='Uploader View', parser_classes=[CSVParser],)
    def uploader(self, request, filename, format=None):
        # Parsed data will be returned within the request object by accessing 'data' attr  
        _data =

        return Response(status=204)

Project's main


from rest_framework import routers
from posts.views import PostsViewSet

router = routers.DefaultRouter()
router.register(r'posts', PostsViewSet)

urlpatterns = [
    url(r'^posts/uploader/(?P<filename>[^/]+)$', PostsViewSet.as_view({'put': 'uploader'}), name='posts_uploader')
    url(r'^', include(router.urls), name='root-api'),


The magic happens when we add @action decorator to our class method 'uploader'. By specifying "methods=['put']" argument, we are only allowing PUT requests; perfect for file uploading.

I also added the argument "parser_classes" to show you can select the parser that will parse your content. I added CSVParser from the rest_framework_csv package, to demonstrate how we can accept only certain type of files if this functionality is required, in my case I'm only accepting "Content-Type: text/csv". Note: If you're adding custom Parsers, you'll need to specify them in parsers_classes in the ViewSet due the request will compare the allowed media_type with main (class) parsers before accessing the uploader method parsers.

Now we need to tell Django how to go to this method and where can be implemented in our urls. That's when we add the fixed url (Simple purposes). This Url will take a "filename" argument that will be passed in the method later on. We need to pass this method "uploader", specifying the http protocol ('PUT') in a list to the PostsViewSet.as_view method.

When we land in the following url 

it will expect a PUT request with headers specifying "Content-Type" and Content-Disposition: attachment; filename="something.csv".

curl -v -u user:pass --upload-file ./something.csv --header "Content-type:text/csv"

How do I code my submit button go to an email address

You might use Form tag with action attribute to submit the mailto.

Here is an example:

<form method="post" action="mailto:[email protected]" >
<input type="submit" value="Send Email" /> 

Get only part of an Array in Java?

The length of an array in Java is immutable. So, you need to copy the desired part as a new array.
Use copyOfRange method from java.util.Arrays class:

int[] newArray = Arrays.copyOfRange(oldArray, startIndex, endIndex);

startIndex is the initial index of the range to be copied, inclusive.
endIndex is the final index of the range to be copied, exclusive. (This index may lie outside the array)


   //index   0   1   2   3   4
int[] arr = {10, 20, 30, 40, 50};
Arrays.copyOfRange(arr, 0, 2);          // returns {10, 20}
Arrays.copyOfRange(arr, 1, 4);          // returns {20, 30, 40}
Arrays.copyOfRange(arr, 2, arr.length); // returns {30, 40, 50} (length = 5)

Finding smallest value in an array most efficiently

Richie's answer is close. It depends upon the language. Here is a good solution for java:

int smallest =  Integer.MAX_VALUE;
int array[]; // Assume it is filled.
int array_length = array.length;
for (int i = array_length - 1; i >= 0; i--) {
    if (array[i] < smallest) {
        smallest = array[i];

I go through the array in reverse order, because comparing "i" to "array_length" in the loop comparison requires a fetch and a comparison (two operations), whereas comparing "i" to "0" is a single JVM bytecode operation. If the work being done in the loop is negligible, then the loop comparison consumes a sizable fraction of the time.

Of course, others pointed out that encapsulating the array and controlling inserts will help. If getting the minimum was ALL you needed, keeping the list in sorted order is not necessary. Just keep an instance variable that holds the smallest inserted so far, and compare it to each value as it is added to the array. (Of course, this fails if you remove elements. In that case, if you remove the current lowest value, you need to do a scan of the entire array to find the new lowest value.)

Is there a way to specify which pytest tests to run from a file?

According to the doc about Run tests by node ids

since you have all node ids in foo.txt, just run

pytest `cat foo.txt | tr '\n' ' '`

this is same with below command (with file content in the question)

pytest tests_directory/ tests_directory/

difference between new String[]{} and new String[] in java

Try this one.

  String[] array1= new String[]{};
  String[] array2= new String[0];

Note: there is no byte code difference between new String[]{}; and new String[0];

new String[]{} is array initialization with values.

new String[0]; is array declaration(only allocating memory)

new String[10]{}; is not allowed because new String[10]{ may be here 100 values};

Getting the folder name from a path

var fullPath = @"C:\folder1\folder2\file.txt";
var lastDirectory = Path.GetDirectoryName(fullPath).Split('\\').LastOrDefault();

Set content of HTML <span> with Javascript

The Maximally Standards Compliant way to do it is to create a text node containing the text you want and append it to the span (removing any currently extant text nodes).

The way I would actually do it is to use jQuery's .text().

Background position, margin-top?

 background-image: url(/images/poster.png);
 background-position: center;
 background-position-y: 50px;
 background-repeat: no-repeat;

What CSS selector can be used to select the first div within another div

If we can assume that the H1 is always going to be there, then

div h1+div {...}

but don't be afraid to specify the id of the content div:

#content h1+div {...}

That's about as good as you can get cross-browser right now without resorting to a JavaScript library like jQuery. Using h1+div ensures that only the first div after the H1 gets the style. There are alternatives, but they rely on CSS3 selectors, and thus won't work on most IE installs.

Add Items to Columns in a WPF ListView

Solution With Less XAML and More C#

If you define the ListView in XAML:

<ListView x:Name="listView"/>

Then you can add columns and populate it in C#:

public Window()
    // Initialize

    // Add columns
    var gridView = new GridView();
    this.listView.View = gridView;
    gridView.Columns.Add(new GridViewColumn { 
        Header = "Id", DisplayMemberBinding = new Binding("Id") });
    gridView.Columns.Add(new GridViewColumn { 
        Header = "Name", DisplayMemberBinding = new Binding("Name") });

    // Populate list
    this.listView.Items.Add(new MyItem { Id = 1, Name = "David" });

See definition of MyItem below.

Solution With More XAML and less C#

However, it's easier to define the columns in XAML (inside the ListView definition):

<ListView x:Name="listView">
            <GridViewColumn Header="Id" DisplayMemberBinding="{Binding Id}"/>
            <GridViewColumn Header="Name" DisplayMemberBinding="{Binding Name}"/>

And then just populate the list in C#:

public Window()
    // Initialize

    // Populate list
    this.listView.Items.Add(new MyItem { Id = 1, Name = "David" });

See definition of MyItem below.

MyItem Definition

MyItem is defined like this:

public class MyItem
    public int Id { get; set; }

    public string Name { get; set; }

Shorthand if/else statement Javascript

You can try if/else this shorthand method:

// Syntax
if condition || else condition

// Example
let oldStr = "";
let newStr = oldStr || "Updated Value";
console.log(newStr); // Updated Value

// Example 2
let num1 = 2;
let num2 = num1 || 3;
console.log(num2);  // 2  cause num1 is a truthy

How to use a switch case 'or' in PHP

I won't repost the other answers because they're all correct, but I'll just add that you can't use switch for more "complicated" statements, eg: to test if a value is "greater than 3", "between 4 and 6", etc. If you need to do something like that, stick to using if statements, or if there's a particularly strong need for switch then it's possible to use it back to front:

switch (true) {
    case ($value > 3) :
        // value is greater than 3
    case ($value >= 4 && $value <= 6) :
        // value is between 4 and 6

but as I said, I'd personally use an if statement there.

random.seed(): What does it do?

Imho, it is used to generate same random course result when you use random.seed(samedigit) again.

In [47]: random.randint(7,10)

Out[47]: 9

In [48]: random.randint(7,10)

Out[48]: 9

In [49]: random.randint(7,10)

Out[49]: 7

In [50]: random.randint(7,10)

Out[50]: 10

In [51]: random.seed(5)

In [52]: random.randint(7,10)

Out[52]: 9

In [53]: random.seed(5)

In [54]: random.randint(7,10)

Out[54]: 9

How to get HTTP response code for a URL in Java?


URL url = new URL("");
HttpURLConnection connection = (HttpURLConnection)url.openConnection();

int code = connection.getResponseCode();

This is by no means a robust example; you'll need to handle IOExceptions and whatnot. But it should get you started.

If you need something with more capability, check out HttpClient.

How to sort an ArrayList in Java

Implement Comparable interface to Fruit.

public class Fruit implements Comparable<Fruit> {

It implements the method

    public int compareTo(Fruit fruit) {
        //write code here for compare name

Then do call sort method


Detecting endianness programmatically in a C++ program

For further details, you may want to check out this codeproject article Basic concepts on Endianness:

How to dynamically test for the Endian type at run time?

As explained in Computer Animation FAQ, you can use the following function to see if your code is running on a Little- or Big-Endian system: Collapse

#define BIG_ENDIAN      0
#define LITTLE_ENDIAN   1
int TestByteOrder()
   short int word = 0x0001;
   char *byte = (char *) &word;
   return(byte[0] ? LITTLE_ENDIAN : BIG_ENDIAN);

This code assigns the value 0001h to a 16-bit integer. A char pointer is then assigned to point at the first (least-significant) byte of the integer value. If the first byte of the integer is 0x01h, then the system is Little-Endian (the 0x01h is in the lowest, or least-significant, address). If it is 0x00h then the system is Big-Endian.

Vlookup referring to table data in a different sheet

Your formula looks fine. Maybe the value you are looking for is not in the first column of the second table?

If the second sheet is in another workbook, you need to add a Workbook reference to your formula:


How to do a PUT request with curl?

An example PUT following Martin C. Martin's comment:

curl -T filename.txt

With -T (same as --upload-file) curl will use PUT for HTTP.

How to access the elements of a 2D array?

If you have this :

a = [[1, 1], [2, 1],[3, 1]]

You can easily access this by using :

a[0][1] = 7

git recover deleted file where no commit was made after the delete

if you used

git rm filename

to delete a file then

git checkout path/to/filename

doesn't work, so in that case

git checkout HEAD^ path/to/filename

should work

Setting the default Java character encoding

From the JVM™ Tool Interface documentation…

Since the command-line cannot always be accessed or modified, for example in embedded VMs or simply VMs launched deep within scripts, a JAVA_TOOL_OPTIONS variable is provided so that agents may be launched in these cases.

By setting the (Windows) environment variable JAVA_TOOL_OPTIONS to -Dfile.encoding=UTF8, the (Java) System property will be set automatically every time a JVM is started. You will know that the parameter has been picked up because the following message will be posted to System.err:

Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF8

How to check if array is not empty?

If you are talking about Python's actual array (available through import array from array), then the principle of least astonishment applies and you can check whether it is empty the same way you'd check if a list is empty.

from array import array
an_array = array('i') # an array of ints

if an_array:
    print("this won't be printed")


if an_array:
    print("this will be printed")

What's the simplest way to list conflicted files in Git?

git diff --name-only --diff-filter=U

AppCompat v7 r21 returning error in values.xml?

I changed

compile ''


compile ''

in build.gradle and after sync I didn't get any errors

Error:Conflict with dependency ''

From Gradle Plugin User Guide:

When instrumentation tests are run, both the main APK and test APK share the same classpath. Gradle build will fail if the main APK and the test APK use the same library (e.g. Guava) but in different versions. If gradle didn't catch that, your app could behave differently during tests and during normal run (including crashing in one of the cases).

To make the build succeed, just make sure both APKs use the same version. If the error is about an indirect dependency (a library you didn't mention in your build.gradle), just add a dependency for the newer version to the configuration

Add this line to your build.gradle dependencies to use newer version for both APKs:


For future reference, you can check your Gradle Console and it will provide a helpful link next to the error to help with any gradle build errors.

jQuery if checkbox is checked

See main difference between ATTR | PROP | IS below:


$( "input" )_x000D_
  .change(function() {_x000D_
    var $input = $( this );_x000D_
    $( "p" ).html( ".attr( 'checked' ): <b>" + $input.attr( "checked" ) + "</b><br>" +_x000D_
      ".prop( 'checked' ): <b>" + $input.prop( "checked" ) + "</b><br>" +_x000D_
      ".is( ':checked' ): <b>" + $ ":checked" ) + "</b>" );_x000D_
p {_x000D_
    margin: 20px 0 0;_x000D_
  b {_x000D_
    color: blue;_x000D_
<meta charset="utf-8">_x000D_
  <title>attr demo</title>_x000D_
  <script src=""></script>_x000D_
<input id="check1" type="checkbox" checked="checked">_x000D_
<label for="check1">Check me</label>_x000D_

Remove all values within one list from another list?

>>> a = range(1, 10)
>>> [x for x in a if x not in [2, 3, 7]]
[1, 4, 5, 6, 8, 9]

How do I create a user account for basic authentication?

I know this is a really old question but I wanted to add a bit of explanation that I discovered the hard way (this is n00b information).

"Basic Authentication" shares the same accounts that you have on your local computer or network. If you leave the domain and realm empty, local accounts are what are actually being used. So to add a new account you follow the exact process you would for adding a normal new user account to your local computer (as answered by JoshM or shown here). If you enter a domain and realm you can create network accounts in your local active directory and these are what will be used to log the user in and out.

Because it has been around for so long, basic authentication is generally compatible with any browser/system out there but it does have to major flaws:

  • user and password are sent in the clear (except over SSL)
  • you need to have a user account for each user or client

For more information about basic authentication or user accounts see the following MSDN page.

Pyspark replace strings in Spark dataframe column

For scala

import org.apache.spark.sql.functions.regexp_replace
import org.apache.spark.sql.functions.col
data.withColumn("addr_new", regexp_replace(col("addr_line"), "\\*", ""))

How do I include inline JavaScript in Haml?

So i tried the above :javascript which works :) However HAML wraps the generated code in CDATA like so:

<script type="text/javascript">
    $(document).ready( function() {
       $('body').addClass( 'test' );
    } );

The following HAML will generate the typical tag for including (for example) typekit or google analytics code.

  //your code goes here - dont forget the indent!

Bootstrap - floating navbar button right

You would need to use the following markup. If you want to float any menu items to the right, create a separate <ul class="nav navbar-nav"> with navbar-right class to it.

<script src=""></script>_x000D_
  <script src=""></script>_x000D_
  <link href="" rel="stylesheet" />_x000D_
  <div class="navbar navbar-inverse navbar-fixed-top" role="navigation">_x000D_
    <div class="container">_x000D_
      <div class="navbar-header">_x000D_
        <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">_x000D_
            <span class="sr-only">Toggle navigation</span>_x000D_
            <span class="icon-bar"></span>_x000D_
            <span class="icon-bar"></span>_x000D_
            <span class="icon-bar"></span>_x000D_
        <a class="navbar-brand" href="#">Project name</a>_x000D_
      <div class="collapse navbar-collapse">_x000D_
        <ul class="nav navbar-nav">_x000D_
          <li class="active"><a href="#">Home</a></li>_x000D_
          <li><a href="#about">About</a></li>_x000D_
        <ul class="nav navbar-nav navbar-right">_x000D_
          <li><a href="#contact">Contact</a></li>_x000D_

415 Unsupported Media Type - POST json to OData service in lightswitch 2012

It looks like this issue has to do with the difference between the Content-Type and Accept headers. In HTTP, Content-Type is used in request and response payloads to convey the media type of the current payload. Accept is used in request payloads to say what media types the server may use in the response payload.

So, having a Content-Type in a request without a body (like your GET request) has no meaning. When you do a POST request, you are sending a message body, so the Content-Type does matter.

If a server is not able to process the Content-Type of the request, it will return a 415 HTTP error. (If a server is not able to satisfy any of the media types in the request Accept header, it will return a 406 error.)

In OData v3, the media type "application/json" is interpreted to mean the new JSON format ("JSON light"). If the server does not support reading JSON light, it will throw a 415 error when it sees that the incoming request is JSON light. In your payload, your request body is verbose JSON, not JSON light, so the server should be able to process your request. It just doesn't because it sees the JSON light content type.

You could fix this in one of two ways:

  1. Make the Content-Type "application/json;odata=verbose" in your POST request, or
  2. Include the DataServiceVersion header in the request and set it be less than v3. For example:

    DataServiceVersion: 2.0;

(Option 2 assumes that you aren't using any v3 features in your request payload.)

What is dtype('O'), in pandas?

It means "a python object", i.e. not one of the builtin scalar types supported by numpy.

=> dtype('O')

How to use java.Set

The first thing you need to study is the java.util.Set API.

Here's a small example of how to use its methods:

    Set<Integer> numbers = new TreeSet<Integer>();


    System.out.println(numbers); // "[2, 5]"
    System.out.println(numbers.contains(7)); // "false"

    System.out.println(numbers.add(5)); // "false"
    System.out.println(numbers.size()); // "2"

    int sum = 0;
    for (int n : numbers) {
        sum += n;
    System.out.println("Sum = " + sum); // "Sum = 7"

    System.out.println(numbers); // "[1, 2, 3, 4, 5]"

    System.out.println(numbers); // "[1, 2, 3]"

    System.out.println(numbers); // "[2, 3]"

Once you're familiar with the API, you can use it to contain more interesting objects. If you haven't familiarized yourself with the equals and hashCode contract, already, now is a good time to start.

In a nutshell:

  • @Override both or none; never just one. (very important, because it must satisfied property: a.equals(b) == true --> a.hashCode() == b.hashCode()
    • Be careful with writing boolean equals(Thing other) instead; this is not a proper @Override.
  • For non-null references x, y, z, equals must be:
    • reflexive: x.equals(x).
    • symmetric: x.equals(y) if and only if y.equals(x)
    • transitive: if x.equals(y) && y.equals(z), then x.equals(z)
    • consistent: x.equals(y) must not change unless the objects have mutated
    • x.equals(null) == false
  • The general contract for hashCode is:
    • consistent: return the same number unless mutation happened
    • consistent with equals: if x.equals(y), then x.hashCode() == y.hashCode()
      • strictly speaking, object inequality does not require hash code inequality
      • but hash code inequality necessarily requires object inequality
  • What counts as mutation should be consistent between equals and hashCode.

Next, you may want to impose an ordering of your objects. You can do this by making your type implements Comparable, or by providing a separate Comparator.

Having either makes it easy to sort your objects (Arrays.sort, Collections.sort(List)). It also allows you to use SortedSet, such as TreeSet.

Further readings on stackoverflow:

How to open generated pdf using jspdf in new window

Based on the source you can use the 'dataurlnewwindow' parameter for output():


Source in github:

All possible cases:

doc.output('save', 'filename.pdf'); //Try to save PDF as a file (not works on ie before 10, and some mobile devices)
doc.output('datauristring');        //returns the data uri string
doc.output('datauri');              //opens the data uri in current window
doc.output('dataurlnewwindow');     //opens the data uri in new window

How to remove an element from the flow?


I mean, other than removing it from the layout entirely with display: none, I'm pretty sure that's it.

Are you facing a particular situation in which position: absolute is not a viable solution?

Using node.js as a simple web server

Express function sendFile does exactly what you need, and since you want web server functionality from node, express comes as natural choice and then serving static files becomes as easy as :


read more here :

A small example with express web server for node:

var express = require('express');
var app = express();
var path = require('path');

app.get('/', function(req, res) {
    res.sendFile(path.join(__dirname + '/index.html'));


run this, and navigate to http://localhost:8080

To expand on this to allow you to serve static files like css and images, here's another example :

var express = require('express');
var app = express();
var path = require('path');

app.use(express.static(__dirname + '/css'));

app.get('/', function(req, res) {
    res.sendFile(path.join(__dirname + '/index.html'));


so create a subfolder called css, put your static content in it, and it will be available to your index.html for easy reference like :

<link type="text/css" rel="stylesheet" href="/css/style.css" />

Notice relative path in href!


How to check if type of a variable is string?

In Python 3.x or Python 2.7.6

if type(x) == str:

How to trim white spaces of array values in php

function trimArray(&$value) 
    $value = trim($value); 
$pmcArray = array('php ','mysql ', ' code ');
array_walk($pmcArray, 'trimArray');

by using array_walk function, we can remove space from array elements and elements return the result in same array.

How to push object into an array using AngularJS

You should try this way. It will definitely work.

(function() {

var app = angular.module('myApp', []);

 app.controller('myController', ['$scope', function($scope) {

    $scope.myText = "Object Push inside ";

    $scope.arrayText = [


    $scope.addText = function() {



In your case $scope.arrayText is an object. You should initialize as a array.

Select a Column in SQL not in Group By

The columns in the result set of a select query with group by clause must be:

  • an expression used as one of the group by criteria , or ...
  • an aggregate function , or ...
  • a literal value

So, you can't do what you want to do in a single, simple query. The first thing to do is state your problem statement in a clear way, something like:

I want to find the individual claim row bearing the most recent creation date within each group in my claims table


create table dbo.some_claims_table
  claim_id     int      not null ,
  group_id     int      not null ,
  date_created datetime not null ,

  constraint some_table_PK primary key ( claim_id                ) ,
  constraint some_table_AK01 unique    ( group_id , claim_id     ) ,
  constraint some_Table_AK02 unique    ( group_id , date_created ) ,


The first thing to do is identify the most recent creation date for each group:

select group_id ,
       date_created = max( date_created )
from dbo.claims_table
group by group_id

That gives you the selection criteria you need (1 row per group, with 2 columns: group_id and the highwater created date) to fullfill the 1st part of the requirement (selecting the individual row from each group. That needs to be a virtual table in your final select query:

select *
from dbo.claims_table t
join ( select group_id ,
       date_created = max( date_created )
       from dbo.claims_table
       group by group_id
      ) x on x.group_id     = t.group_id
         and x.date_created = t.date_created

If the table is not unique by date_created within group_id (AK02), you you can get duplicate rows for a given group.

How do I get rid of the "cannot empty the clipboard" error?

I copied a picture (instead of text) that I had in my excel 2007 file and that solved the problem for me. The picture copied to the (then empty) clipboard. I could then copy cells normally even after clearing the clipboard of the picture. I think a graph object should also do the trick.

Append a tuple to a list - what's the difference between two ways?

I believe tuple() takes a list as an argument For example,

tuple([1,2,3]) # returns (1,2,3)

see what happens if you wrap your array with brackets

Start a fragment via Intent within a Fragment

Try this it may help you:

public void ButtonClick(View view) {
    Fragment mFragment = new YourNextFragment(); 
    getSupportFragmentManager().beginTransaction().replace(, mFragment).commit();

"No cached version... available for offline mode."

Had the same error after updating Android Studio today. For me, it wasn't a matter of proxy settings:

  1. Uncheck "Offline work" in Android Studio 0.6.0:

    File->Settings->Gradle->Global Gradle Settings

    or in OSX:

    Preferences->Gradle->Global Gradle Setting

    or in more recent versions:

    File->Settings->Build, Execution, Deployment->Build tools->Gradle

  2. Resync the project, for example by restarting the Android Studio

  3. Once synced, you can check the option again to work offline.

(Only tested in Gradle version 0.11... and Android Studio version 0.6.0 Preview)

EDIT : Added paths for different versions/platforms (as mentioned by John Ballinger and The_Martian). Not yet verified.

Reading from file using read() function

Read Byte by Byte and check that each byte against '\n' if it is not, then store it into buffer
if it is '\n' add '\0' to buffer and then use atoi()

You can read a single byte like this

char c;

See read()

PHP random string generator

First, you define the alphabet you want to use:

$alphanum = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
$special  = '~!@#$%^&*(){}[],./?';
$alphabet = $alphanum . $special;

Then, use openssl_random_pseudo_bytes() to generate proper random data:

$len = 12; // length of password
$random = openssl_random_pseudo_bytes($len);

Finally, you use this random data to create the password. Because each character in $random can be chr(0) until chr(255), the code uses the remainder after division of its ordinal value with $alphabet_length to make sure only characters from the alphabet are picked (note that doing so biases the randomness):

$alphabet_length = strlen($alphabet);
$password = '';
for ($i = 0; $i < $len; ++$i) {
    $password .= $alphabet[ord($random[$i]) % $alphabet_length];

Alternatively, and generally better, is to use RandomLib and SecurityLib:

use SecurityLib\Strength;

$factory = new RandomLib\Factory;
$generator = $factory->getGenerator(new Strength(Strength::MEDIUM));

$password = $generator->generateString(12, $alphabet);

Javascript - Append HTML to container element without innerHTML

How to fish and while using strict code. There are two prerequisite functions needed at the bottom of this post.

xml_add('before', id_('element_after'), '<span xmlns="">Some text.</span>');

xml_add('after', id_('element_before'), '<input type="text" xmlns="" />');

xml_add('inside', id_('element_parent'), '<input type="text" xmlns="" />');

Add multiple elements (namespace only needs to be on the parent element):

xml_add('inside', id_('element_parent'), '<div xmlns=""><input type="text" /><input type="button" /></div>');

Dynamic reusable code:

function id_(id) {return (document.getElementById(id)) ? document.getElementById(id) : false;}

function xml_add(pos, e, xml)
 e = (typeof e == 'string' && id_(e)) ? id_(e) : e;

 if (e.nodeName)
  if (pos=='after') {e.parentNode.insertBefore(document.importNode(new DOMParser().parseFromString(xml,'application/xml').childNodes[0],true),e.nextSibling);}
  else if (pos=='before') {e.parentNode.insertBefore(document.importNode(new DOMParser().parseFromString(xml,'application/xml').childNodes[0],true),e);}
  else if (pos=='inside') {e.appendChild(document.importNode(new DOMParser().parseFromString(xml,'application/xml').childNodes[0],true));}
  else if (pos=='replace') {e.parentNode.replaceChild(document.importNode(new DOMParser().parseFromString(xml,'application/xml').childNodes[0],true),e);}
  //Add fragment and have it returned.

How to enable mbstring from php.ini?

All XAMPP packages come with Multibyte String (php_mbstring.dll) extension installed.

If you have accidentally removed DLL file from php/ext folder, just add it back (get the copy from XAMPP zip archive - its downloadable).

If you have deleted the accompanying INI configuration line from php.ini file, add it back as well:


Also, ensure to restart your webserver (Apache) using XAMPP control panel.

Additional Info on Enabling PHP Extensions

  • install extension (e.g. put php_mbstring.dll into /XAMPP/php/ext directory)
  • in php.ini, ensure extension directory specified (e.g. extension_dir = "ext")
  • ensure correct build of DLL file (e.g. 32bit thread-safe VC9 only works with DLL files built using exact same tools and configuration: 32bit thread-safe VC9)
  • ensure PHP API versions match (If not, once you restart the webserver you will receive related error.)

SQL Server: Invalid Column Name

Whenever this happens to me, I press Ctrl+Shift+R which refreshes intellisense, close the query window (save if necessary), then start a new session which usually works quite well.

Document directory path of Xcode Device Simulator

For Swift 3.x

if let documentsPath = FileManager.default.urls(for:.documentDirectory, in: .userDomainMask).first?.path {
        print("Documents Directory: " + documentsPath)

how to customise input field width in bootstrap 3

You can use these classes





for input fields and replace input with btn for buttons.

Check this documentation

This will change only height of the element, to reduce the width you have to use grid system classes like col-xs-* col-md-* col-lg-*.

Example col-md-3. See doc here

How to correctly write async method?

To get the behavior you want you need to wait for the process to finish before you exit Main(). To be able to tell when your process is done you need to return a Task instead of a void from your function, you should never return void from a async function unless you are working with events.

A re-written version of your program that works correctly would be

class Program {     static void Main(string[] args)     {         Debug.WriteLine("Calling DoDownload");         var downloadTask = DoDownloadAsync();         Debug.WriteLine("DoDownload done");         downloadTask.Wait(); //Waits for the background task to complete before finishing.      }      private static async Task DoDownloadAsync()     {         WebClient w = new WebClient();          string txt = await w.DownloadStringTaskAsync("");         Debug.WriteLine(txt);     } } 

Because you can not await in Main() I had to do the Wait() function instead. If this was a application that had a SynchronizationContext I would do await downloadTask; instead and make the function this was being called from async.

https with WCF error: "Could not find base address that matches scheme https"

In my case i am setting security mode to "TransportCredentialOnly" instead of "Transport" in binding. Changing it resolved the issue

    <binding name="webHttpSecure">
      <security mode="Transport">
        <transport clientCredentialType="Windows" ></transport>

Why does this iterative list-growing code give IndexError: list assignment index out of range?

You could also use a list comprehension:

j = [l for l in i]

or make a copy of it using the statement:

j = i[:]

What does the servlet <load-on-startup> value signify

  1. If value is same for two servlet than they will be loaded in an order on which they are declared inside web.xml file.
  2. if is 0 or negative integer than Servlet will be loaded when Container feels to load them.
  3. guarantees loading, initialization and call to init() method of servlet by web container.
  4. If there is no element for any servlet than they will be loaded when web container decides to load them.

Why do I need to override the equals and hashCode methods in Java?

To help you check for duplicate Objects, we need a custom equals and hashCode.

Since hashcode always returns a number its always fast to retrieve an object using a number rather than an alphabetic key. How will it do? Assume we created a new object by passing some value which is already available in some other object. Now the new object will return the same hash value as of another object because the value passed is same. Once the same hash value is returned, JVM will go to the same memory address every time and if in case there are more than one objects present for the same hash value it will use equals() method to identify the correct object.

Difference between Ctrl+Shift+F and Ctrl+I in Eclipse

Ctrl+Shift+F formats the selected line(s) or the whole source code if you haven't selected any line(s) as per the format specified in your Eclipse, while Ctrl+I gives proper indent to the selected line(s) or the current line if you haven't selected any line(s). try this. or more precisely

The Ant editor that ships with Eclipse can be used to reformat

XML/XHTML/HTML code (with a few configuration options in Window > Preferences > Ant > Editor).

You can right-click a file then

Open With... > Other... > Internal Editors > Ant Editor

Or add a file association between .html (or .xhtml) and that editor with

Window > Preferences > General > Editors > File Associations

Once open in the editor, hit ESC then CTRL-F to reformat.

Retrieving the COM class factory for component with CLSID {XXXX} failed due to the following error: 80040154

It sounds like your service was built against 'Any CPU', causing you errors on 64-bit where you are using COM components. You need to build it for x86.

The website is probably running as a 32-bit process which is why it can use the component. Building your solution against x86 will force your service to run as 32-bit.

How can I add new item to the String array?

You can't. A Java array has a fixed length. If you need a resizable array, use a java.util.ArrayList<String>.

BTW, your code is invalid: you don't initialize the array before using it.

Check if an excel cell exists on another worksheet in a column - and return the contents of a different column

You can use following formulas.

For Excel 2007 or later:


For Excel 2003:

=IF(ISERROR(MATCH(D3,List!A:A, 0)), "No Match", VLOOKUP(D3,List!A:C,3,FALSE))

Note, that

  • I'm using List!A:C in VLOOKUP and returns value from column ? 3
  • I'm using 4th argument for VLOOKUP equals to FALSE, in that case VLOOKUP will only find an exact match, and the values in the first column of List!A:C do not need to be sorted (opposite to case when you're using TRUE).

How to export a CSV to Excel using Powershell

I had some problem getting the other examples to work.

EPPlus and other libraries produces OpenDocument Xml format, which is not the same as you get when you save from Excel as xlsx.

macks example with open CSV and just re-saving didn't work, I never managed to get the ',' delimiter to be used correctly.

Ansgar Wiechers example has some slight error which I found the answer for in the commencts.

Anyway, this is a complete working example. Save this in a File CsvToExcel.ps1

param (

$excel = New-Object -ComObject Excel.Application
$excel.Visible = $false

$wb = $excel.Workbooks.Add()
$ws = $wb.Sheets.Item(1)

$ws.Cells.NumberFormat = "@"

write-output "Opening $inputfile"

$i = 1
Import-Csv $inputfile | Foreach-Object { 
    $j = 1
    foreach ($prop in $_.PSObject.Properties)
        if ($i -eq 1) {
            $ws.Cells.Item($i, $j) = $prop.Name
        } else {
            $ws.Cells.Item($i, $j) = $prop.Value

write-output "Success"

Execute with:

.\CsvToExcel.ps1 -inputfile "C:\Temp\X\data.csv" -outputfile "C:\Temp\X\data.xlsx"

Gradle Error:Execution failed for task ':app:processDebugGoogleServices'

if you got an error

Execution failed for task ‘:app:fabricGenerateResourcesDebug’. Crashlytics Developer Tools error.

remove also this line:

apply plugin: 'io.fabric'

Django upgrading to 1.9 error "AppRegistryNotReady: Apps aren't loaded yet."

django.setup() in the top will not work while you are running a script explicitly. My problem solved when I added this in the bottom of the settings file

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
import sys
if BASE_DIR not in sys.path:
os.environ['DJANGO_SETTINGS_MODULE'] =  "igp_lrpe.settings"
os.environ.setdefault("DJANGO_SETTINGS_MODULE", "igp_lrpe.settings")
import django

How to cat <<EOF >> a file containing code?

You only need a minimal change; single-quote the here-document delimiter after <<.

cat <<'EOF' >>

or equivalently backslash-escape it:

cat <<\EOF >>

Without quoting, the here document will undergo variable substitution, backticks will be evaluated, etc, like you discovered.

If you need to expand some, but not all, values, you need to individually escape the ones you want to prevent.

cat <<EOF >>
# Created on $(date # : <<-- this will be evaluated before cat;)
echo "\$HOME will not be evaluated because it is backslash-escaped"

will produce

# Created on Fri Feb 16 11:00:18 UTC 2018
echo "$HOME will not be evaluated because it is backslash-escaped"

As suggested by @fedorqui, here is the relevant section from man bash:

Here Documents

This type of redirection instructs the shell to read input from the current source until a line containing only delimiter (with no trailing blanks) is seen. All of the lines read up to that point are then used as the standard input for a command.

The format of here-documents is:


No parameter expansion, command substitution, arithmetic expansion, or pathname expansion is performed on word. If any characters in word are quoted, the delimiter is the result of quote removal on word, and the lines in the here-document are not expanded. If word is unquoted, all lines of the here-document are subjected to parameter expansion, command substitution, and arithmetic expansion. In the latter case, the character sequence \<newline> is ignored, and \ must be used to quote the characters \, $, and `.

Proper way to use **kwargs in Python

While most answers are saying that, e.g.,

def f(**kwargs):
    foo = kwargs.pop('foo')
    bar = kwargs.pop('bar')

is "the same as"

def f(foo=None, bar=None, **kwargs):

this is not true. In the latter case, f can be called as f(23, 42), while the former case accepts named arguments only -- no positional calls. Often you want to allow the caller maximum flexibility and therefore the second form, as most answers assert, is preferable: but that is not always the case. When you accept many optional parameters of which typically only a few are passed, it may be an excellent idea (avoiding accidents and unreadable code at your call sites!) to force the use of named arguments -- threading.Thread is an example. The first form is how you implement that in Python 2.

The idiom is so important that in Python 3 it now has special supporting syntax: every argument after a single * in the def signature is keyword-only, that is, cannot be passed as a positional argument, but only as a named one. So in Python 3 you could code the above as:

def f(*, foo=None, bar=None, **kwargs):

Indeed, in Python 3 you can even have keyword-only arguments that aren't optional (ones without a default value).

However, Python 2 still has long years of productive life ahead, so it's better to not forget the techniques and idioms that let you implement in Python 2 important design ideas that are directly supported in the language in Python 3!

How to exit an application properly

in this case I start Outlook and then close it

Dim ol 

Set ol = WScript.CreateObject("Outlook.Application") 'Starts Outlook

ol.quit 'Closes Outlook

Read the package name of an Android APK

A simple solution would be Open Android Studio -> Build -> Analyze Apk... browse and select the APK now you can find the package name and pretty much you can read.

How to make image hover in css?

Simply this, no extra div or JavaScript needed, just pure CSS (jsfiddle demo):


<a href="javascript:alert('Hello!')" class="changesImgOnHover">
    <img src="!" alt="Hello!">


.changesImgOnHover {
    display: inline-block; /* or just block */
    width: 50px;
    background: url('!') no-repeat;
.changesImgOnHover:hover img {
    visibility: hidden;

jQuery how to bind onclick event to dynamically added HTML element

All of these methods are deprecated. You should use the on method to solve your problem.

If you want to target a dynamically added element you'll have to use

$(document).on('click', selector-to-your-element , function() {
     //code here ....

this replace the deprecated .live() method.

Google Map API - Removing Markers

You can try this


Hope it works.

How to add new activity to existing project in Android Studio?

In Android Studio 2, just right click on app and select New > Activity > ... to create desired activity type.

enter image description here

Error:Failed to open zip file. Gradle's dependency cache may be corrupt

There are Following Steps to solve this issue.

1. Go to C:\Users\ ~User Name~ \.gradle\wrapper\dists.
2. Delete all the files and folders from dists folder.
3. If Android Studio is Opened then Close any opened project and Reopen the project. The Android Studio Will automatic download all the required files.

(The required time is as per your Internet Speed (Download Size will be about "89 MB"). To see the progress of the downloading Go to C:\Users\ ~User Name~ \.gradle\wrapper\dists folder and check the size of the folder.)

What is the error "Every derived table must have its own alias" in MySQL?

I think it's asking you to do this:

      FROM (SELECT * FROM TT2) as myalias
     ) as anotheralias;

But why would you write this query in the first place?

How to set the JSTL variable value in javascript?

<script ...
   var someJsVar = "<c:out value='${someJstLVarFromBackend}'/>";


This works even if you dont have a hidden/non-hidden input field set somewhere in the jsp.

Twitter Bootstrap Modal Form Submit

Updated 2018

Do you want to close the modal after submit? Whether the form in inside the modal or external to it you should be able to use jQuery ajax to submit the form.

Here is an example with the form inside the modal:

<a href="#myModal" role="button" class="btn" data-toggle="modal">Launch demo modal</a>

<div id="myModal" class="modal hide fade" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
    <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
            <h3 id="myModalLabel">Modal header</h3>
    <div class="modal-body">
        <form id="myForm" method="post">
          <input type="hidden" value="hello" id="myField">
            <button id="myFormSubmit" type="submit">Submit</button>
    <div class="modal-footer">
        <button class="btn" data-dismiss="modal" aria-hidden="true">Close</button>
        <button class="btn btn-primary">Save changes</button>

And the jQuery ajax to get the form fields and submit it..

         function(data, status, xhr){
           // do something here with response;

Bootstrap 3 example

Bootstrap 4 example

What is the difference between and re.match?

match is much faster than search, so instead of doing"word") you can do regex.match((.*?)word(.*?)) and gain tons of performance if you are working with millions of samples.

This comment from @ivan_bilan under the accepted answer above got me thinking if such hack is actually speeding anything up, so let's find out how many tons of performance you will really gain.

I prepared the following test suite:

import random
import re
import string
import time

LIST_SIZE = 1000000

def generate_word():
    word = [random.choice(string.ascii_lowercase) for _ in range(LENGTH)]
    word = ''.join(word)
    return word

wordlist = [generate_word() for _ in range(LIST_SIZE)]

start = time.time()
['python', word) for word in wordlist]
print('search:', time.time() - start)

start = time.time()
[re.match('(.*?)python(.*?)', word) for word in wordlist]
print('match:', time.time() - start)

I made 10 measurements (1M, 2M, ..., 10M words) which gave me the following plot:

match vs. search regex speedtest line plot

The resulting lines are surprisingly (actually not that surprisingly) straight. And the search function is (slightly) faster given this specific pattern combination. The moral of this test: Avoid overoptimizing your code.

How to resize a custom view programmatically?

This works for me:

ViewGroup.LayoutParams params = layout.getLayoutParams();
params.height = customHeight;

Javascript checkbox onChange

The following solution makes use of jquery. Let's assume you have a checkbox with id of checkboxId.

const checkbox = $("#checkboxId");

checkbox.change(function(event) {
    var checkbox =;
    if (checkbox.checked) {
        //Checkbox has been checked
    } else {
        //Checkbox has been unchecked

Filter an array using a formula (without VBA)

This will do it if you only want the first "B" value, you can sub a cell address for "B" if you want to make it more generic.


To use this based on two columns, just concatenate inside the match:


How to split a file into equal parts, without breaking individual lines?

I made a bash script, that given a number of parts as input, split a file



for i in $(seq 0 $((parts_total-2))); do
  lines=$(wc -l "$input" | cut -f 1 -d" ")
  #n is rounded, 1.3 to 2, 1.6 to 2, 1 to 1
  n=$(awk  -v lines=$lines -v parts=$parts 'BEGIN { 
    n = lines/parts;
    rounded = sprintf("%.0f", n);
      print rounded + 1;
      print rounded;
  head -$n "$input" > split${i}
  tail -$((lines-n)) "$input" > .tmp${i}
mv .tmp$((parts_total-2)) split$((parts_total-1))
rm .tmp*

I used head and tail commands, and store in tmp files, for split the files

#10 means 10 parts
sh input_file 10

or with awk, where 0.1 is 10% => 10 parts, or 0.334 is 3 parts

awk -v size=$(wc -l < input) -v perc=0.1 '{
  nfile = int(NR/(size*perc)); 
  if(nfile >= 1/perc){
  print > "split_"nfile
}' input

How to run a .awk file?

Put the part from BEGIN....END{} inside a file and name it like my.awk.

And then execute it like below:

awk -f my.awk life.csv >output.txt

Also I see a field separator as ,. You can add that in the begin block of the .awk file as FS=","

Preserve Line Breaks From TextArea When Writing To MySQL

Here is what I use

$textToStore = nl2br(htmlentities($inputText, ENT_QUOTES, 'UTF-8'));

$inputText is the text provided by either the form or textarea. $textToStore is the returned text from nl2br and htmlentities, to be stored in your database. ENT_QUOTES will convert both double and single quotes, so you'll have no trouble with those.

Gradle does not find tools.jar

Found it. System property 'java.home' is not JAVA_HOME environment variable. JAVA_HOME points to the JDK, while java.home points to the JRE. See that page for more info.

Soo... My problem was that my startpoint was the jre folder (C:\jdk1.6.0_26\jre) and not the jdk folder (C:\jdk1.6.0_26) as I thought(tools.jar is on the C:\jdk1.6.0_26\lib folder ). The compile line in dependencies.gradle should be:

compile files("${['java.home']}/../lib/tools.jar")

C++ printing boolean, what is displayed?

0 will get printed.

As in C++ true refers to 1 and false refers to 0.

In case, you want to print false instead of 0,then you have to sets the boolalpha format flag for the str stream.

When the boolalpha format flag is set, bool values are inserted/extracted by their textual representation: either true or false, instead of integral values.

#include <iostream>
int main()
  std::cout << std::boolalpha << false << std::endl;




performSelector may cause a leak because its selector is unknown

Here is an updated macro based on the answer given above. This one should allow you to wrap your code even with a return statement.

#define SUPPRESS_PERFORM_SELECTOR_LEAK_WARNING(code)                        \
    _Pragma("clang diagnostic push")                                        \
    _Pragma("clang diagnostic ignored \"-Warc-performSelector-leaks\"")     \
    code;                                                                   \
    _Pragma("clang diagnostic pop")                                         \

    return [_target performSelector:_action withObject:self]

Including jars in classpath on commandline (javac or apt)

Note for Windows users, the jars should be separated by ; and not :.

for example: javac -cp external_libs\lib1.jar;other\lib2.jar;

How do I find which rpm package supplies a file I'm looking for?

You can do this alike here but with your package. In my case, it was lsb_release

Run: yum whatprovides lsb_release


redhat-lsb-core-4.1-24.el7.i686 : LSB Core module support
Repo        : rhel-7-server-rpms
Matched from:
Filename    : /usr/bin/lsb_release

redhat-lsb-core-4.1-24.el7.x86_64 : LSB Core module support
Repo        : rhel-7-server-rpms
Matched from:
Filename    : /usr/bin/lsb_release

redhat-lsb-core-4.1-27.el7.i686 : LSB Core module support
Repo        : rhel-7-server-rpms
Matched from:
Filename    : /usr/bin/lsb_release

redhat-lsb-core-4.1-27.el7.x86_64 : LSB Core module support
Repo        : rhel-7-server-rpms
Matched from:
Filename    : /usr/bin/lsb_release`

Run to install: yum install redhat-lsb-core

The package name SHOULD be without number and system type so yum packager can choose what is best for him.

How do I implement Toastr JS?

This is a simple way to do it!

<link href="" rel="stylesheet"/>
<script src=""></script>
function notificationme(){
toastr.options = {
            "closeButton": false,
            "debug": false,
            "newestOnTop": false,
            "progressBar": true,
            "preventDuplicates": true,
            "onclick": null,
            "showDuration": "100",
            "hideDuration": "1000",
            "timeOut": "5000",
            "extendedTimeOut": "1000",
            "showEasing": "swing",
            "hideEasing": "linear",
            "showMethod": "show",
            "hideMethod": "hide"
        };'MY MESSAGE!');

What's alternative to angular.copy in Angular

I have created a service to use with Angular 5 or higher, it uses the angular.copy() the base of angularjs, it works well for me. Additionally, there are other functions like isUndefined, etc. I hope it helps. Like any optimization, it would be nice to know. regards

import { Injectable } from '@angular/core';

@Injectable({providedIn: 'root'})
export class AngularService {

  private TYPED_ARRAY_REGEXP = /^\[object (?:Uint8|Uint8Clamped|Uint16|Uint32|Int8|Int16|Int32|Float32|Float64)Array\]$/;
  private stackSource = [];
  private stackDest = [];

  constructor() { }

  public isNumber(value: any): boolean {
    if ( typeof value === 'number' ) { return true; }
    else { return false; }

  public isTypedArray(value: any) {
    return value && this.isNumber(value.length) && this.TYPED_ARRAY_REGEXP.test(;

  public isArrayBuffer(obj: any) {
    return === '[object ArrayBuffer]';

  public isUndefined(value: any) {return typeof value === 'undefined'; }

  public isObject(value: any) {  return value !== null && typeof value === 'object'; }

  public isBlankObject(value: any) {
    return value !== null && typeof value === 'object' && !Object.getPrototypeOf(value);

  public isFunction(value: any) { return typeof value === 'function'; }

  public setHashKey(obj: any, h: any) {
    if (h) { obj.$$hashKey = h; }
    else { delete obj.$$hashKey; }

  private isWindow(obj: any) { return obj && obj.window === obj; }

  private isScope(obj: any) { return obj && obj.$evalAsync && obj.$watch; }

  private copyRecurse(source: any, destination: any) {

    const h = destination.$$hashKey;

    if (Array.isArray(source)) {
      for (let i = 0, ii = source.length; i < ii; i++) {
    } else if (this.isBlankObject(source)) {
      for (const key of Object.keys(source)) {
        destination[key] = this.copyElement(source[key]);
    } else if (source && typeof source.hasOwnProperty === 'function') {
      for (const key of Object.keys(source)) {
        destination[key] = this.copyElement(source[key]);
    } else {
      for (const key of Object.keys(source)) {
        destination[key] = this.copyElement(source[key]);
    this.setHashKey(destination, h);
    return destination;

  private copyElement(source: any) {

    if (!this.isObject(source)) {
      return source;

    const index = this.stackSource.indexOf(source);

    if (index !== -1) {
      return this.stackDest[index];

    if (this.isWindow(source) || this.isScope(source)) {
      throw console.log('Cant copy! Making copies of Window or Scope instances is not supported.');

    let needsRecurse = false;
    let destination = this.copyType(source);

    if (destination === undefined) {
      destination = Array.isArray(source) ? [] : Object.create(Object.getPrototypeOf(source));
      needsRecurse = true;


    return needsRecurse
      ? this.copyRecurse(source, destination)
      : destination;

  private copyType = (source: any) => {

    switch ( {
      case '[object Int8Array]':
      case '[object Int16Array]':
      case '[object Int32Array]':
      case '[object Float32Array]':
      case '[object Float64Array]':
      case '[object Uint8Array]':
      case '[object Uint8ClampedArray]':
      case '[object Uint16Array]':
      case '[object Uint32Array]':
        return new source.constructor(this.copyElement(source.buffer), source.byteOffset, source.length);

      case '[object ArrayBuffer]':
        if (!source.slice) {
          const copied = new ArrayBuffer(source.byteLength);
          new Uint8Array(copied).set(new Uint8Array(source));
          return copied;
        return source.slice(0);

      case '[object Boolean]':
      case '[object Number]':
      case '[object String]':
      case '[object Date]':
        return new source.constructor(source.valueOf());

      case '[object RegExp]':
        const re = new RegExp(source.source, source.toString().match(/[^\/]*$/)[0]);
        re.lastIndex = source.lastIndex;
        return re;

      case '[object Blob]':
        return new source.constructor([source], {type: source.type});

    if (this.isFunction(source.cloneNode)) {
      return source.cloneNode(true);

  public copy(source: any, destination?: any) {

    if (destination) {
      if (this.isTypedArray(destination) || this.isArrayBuffer(destination)) {
        throw console.log('Cant copy! TypedArray destination cannot be mutated.');
      if (source === destination) {
        throw console.log('Cant copy! Source and destination are identical.');

      if (Array.isArray(destination)) {
        destination.length = 0;
      } else {
        destination.forEach((value: any, key: any) => {
          if (key !== '$$hashKey') {
            delete destination[key];

      return this.copyRecurse(source, destination);

    return this.copyElement(source);

HTTP Ajax Request via HTTPS Page

I've created a module called cors-bypass, that allows you to do this without the need for a server. It uses postMessage to send cross-domain events, which is used to provide mock HTTP APIs (fetch, WebSocket, XMLHTTPRequest etc.).

It fundamentally does the same as the answer by Endless, but requires no code changes to use it.

Example usage:

import { Client, WebSocket } from 'cors-bypass'

const client = new Client()

await client.openServerInNewTab({
  serverUrl: '',
  adapterUrl: ''

const ws = new WebSocket('ws://')
ws.onopen = () => ws.send('hello')
ws.onmessage = ({ data }) => console.log('received', data)

Are there pointers in php?

PHP can use something like pointers:


Now $y acts like a pointer to $x and $y[0] dereferences a pointer.

The value array(&$x) is just a value, so it can be passed to functions, stored in other arrays, copied to other variables, etc. You can even create a pointer to this pointer variable. (Serializing it will break the pointer, however.)

How to implement a simple scenario the OO way

The approach I would take is: when reading the chapters from the database, instead of a collection of chapters, use a collection of books. This will have your chapters organised into books and you'll be able to use information from both classes to present the information to the user (you can even present it in a hierarchical way easily when using this approach).

Write a file in external storage in Android

The code below creates a Documents directory and then a sub-directory for the application and saved the files to it.

public class loadDataTooDisk extends AsyncTask<String, Integer, String> {
    String sdCardFileTxt;
    protected String doInBackground(String... params)

        //check to see if external storage is avalibel
        if(canW == canR == true)
            //get the path to sdcard 
            File pathToExternalStorage = Environment.getExternalStorageDirectory();
            //to this path add a new directory path and create new App dir (InstroList) in /documents Dir
            File appDirectory = new File(pathToExternalStorage.getAbsolutePath()  + "/documents/InstroList");
            // have the object build the directory structure, if needed.
            //test to see if it is a Text file
            if ( myNewFileName.endsWith(".txt") )

                //Create a File for the output file data
                File saveFilePath = new File (appDirectory, myNewFileName);
                //Adds the textbox data to the file
                    String newline = "\r\n";
                    FileOutputStream fos = new FileOutputStream (saveFilePath);
                    OutputStreamWriter OutDataWriter  = new OutputStreamWriter(fos);

                    OutDataWriter.write(equipNo.getText() + newline);
                    // OutDataWriter.append(equipNo.getText() + newline);
                    OutDataWriter.append(equip_Type.getText() + newline);
                    OutDataWriter.append(equip_Make.getText()+ newline);
                    OutDataWriter.append(equipModel_No.getText()+ newline);
                    OutDataWriter.append(equip_Password.getText()+ newline);
                    OutDataWriter.append(equipWeb_Site.getText()+ newline);


                }catch(Exception e){
        return null;

This one builds the file name

   private String BuildNewFileName()
    { // creates a new filr name
        Time today = new Time(Time.getCurrentTimezone());

        StringBuilder sb = new StringBuilder();

        sb.append(today.year + "");                // Year)
        sb.append(today.monthDay + "");          // Day of the month (1-31)
        sb.append(today.month + "");              // Month (0-11))
        sb.append(today.format("%k:%M:%S"));      // Current time
        sb.append(".txt");                      //Completed file name

        myNewFileName = sb.toString();
        //Replace (:) with (_)
        myNewFileName = myNewFileName.replaceAll(":", "_");

        return myNewFileName;

Hope this helps! It took me a long time to get it working.

How to vertically align text inside a flexbox?

The most voted answer is for solving this specific problem posted by OP, where the content (text) was being wrapped inside an inline-block element. Some cases may be about centering a normal element vertically inside a container, which also applied in my case, so for that all you need is:

align-self: center;

Skip first entry in for loop in python?

Well, your syntax isn't really Python to begin with.

Iterations in Python are over he contents of containers (well, technically it's over iterators), with a syntax for item in container. In this case, the container is the cars list, but you want to skip the first and last elements, so that means cars[1:-1] (python lists are zero-based, negative numbers count from the end, and : is slicing syntax.

So you want

for c in cars[1:-1]:
    do something with c

Remove Duplicate objects from JSON Array

Here's a short one-liner with es6!

const nums = [

Set is a new data object introduced in ES6. Because Set only lets you store unique values. When you pass in an array, it will remove any duplicate values.

export const $uniquenums = [ Set(nums)].sort(); 

Setting up an MS-Access DB for multi-user access

I find the answers to this question to be problematic, confusing and incomplete, so I'll make an effort to do better.

Q1: How can we make sure that the write-user can make changes to the table data while other users use the data? Do the read-users put locks on tables? Does the write-user have to put locks on the table? Does Access do this for us or do we have to explicitly code this?

Nobody has really answered this in any complete fashion. The information on setting locks in the Access options has nothing to do with read vs. write locking. No Locks vs. All Records vs. Edited Record is how you set the default record locking for WRITES.

  • No locks means you are using OPTIMISTIC locking, which means you allow multiple users to edit the record and then inform them after the fact if the record has changed since they launched their own edits. Optimistic locking is what you should start with as it requires no coding to implement it, and for small users populations it hardly ever causes a problem.

  • All Records means that the whole table is locked any time an edit is launched.

  • Edited Record means that fewer records are locked, but whether or not it's a single record or more than one record depends on whether your database is set up to use record-level locking (first added in Jet 4) or page-level locking. Frankly, I've never thought it worth the trouble to set up record-level locking, as optimistic locking takes care of most of the problems.

One might think that you want to use record-level pessimistic locking, but the fact is that in the vast majority of apps, two users are almost never editing the same record. Now, obviously, certain kinds of apps might be exceptions to that, but if I ran into such an app, I'd likely try to engineer it away by redesigning the schema so that it would be very uncommon for two users to edit the same record (usually by going to some form of transactional editing instead, where changes are made by adding records, rather than editing the existing data).

Now, for your actual question, there are a number of ways to accomplish restricting some users to read-only and granting others write privileges. Jet user-level security was intended for this purpose and works fine insofar as it's "security" for any meaningful definition of the term. In general, as long as you're using a Jet/ACE data store, the best security you're going to get is that provided by Jet ULS. It's crackable, yes, but your users would be committing a firable offense by breaking it, so it might be sufficient.

I would tend to not implement Jet ULS at all and instead just architect the data editing forms such that they checked the user's Windows logon and made the forms read-only or writable depending on which users are supposed to get which access. Whether or not you want to record group membership in a data table, or maintain Windows security groups for this purpose is up to you. You could also use a Jet workgroup file to deal with it, and provide a different system.mdw file for the write users. The read-only users would log on transparently as admin, and those logged on as admin would be granted only read-only access. The write users would log on as some other username (transparently, in the shortcut you provide them for launching the app, supplying no password), and that would be used to set up the forms as read or write.

If you use Jet ULS, it can become really hairy to get it right. It involves locking down all the tables as read-only (or maybe not even that) and then using RWOP queries to provide access to the data. I haven't done but one such app in my 14 years of professional Access development.

To summarize my answers to the parts of your question:

How can we make sure that the write-user can make changes to the table data while other users use the data?

I would recommend doing this in the application, setting forms to read/only or editable at runtime depending on the user logon. The easiest approach is to set your forms to be read-only and change to editable for the write users when they open the form.

Do the read-users put locks on tables?

Not in any meaningful sense. Jet/ACE does have read locks, but they are there only for the purpose of maintaining state for individual views, and for refreshing data for the user. They do not lock out write operations of any kind, though the overhead of tracking them theoretically slows things down. It's not enough to worry about.

Does the write-user have to put locks on the table?

Access in combination with Jet/ACE does this for you automatically, particularly if you choose optimistic locking as your default. The key point here is that Access apps are databound, so as soon as a form is loaded, the record has a read lock, and as soon as the record is edited, whether or not it is write-locked for other users is determined by whether you are using optimistic or pessimistic locking. Again, this is the kind of thing Access takes care of for you with its default behaviors in bound forms. You don't worry about any of it until the point at which you encounter problems.

Does Access do this for us or do we have to explicitly code this?

Basically, other than setting editability at runtime (according to who has write access), there is no coding necessary if you're using optimistic locking. With pessimistic locking, you don't have to code, but you will almost always need to, as you can't just leave the user stuck with the default behaviors and error messages.

Q2: Are there any common problems with "MS Access transactions" that we should be aware of?

Jet/ACE has support for commit/rollback transactions, but it's not clear to me if that's what you mean in this question. In general, I don't use transactions except for maintaining atomicity, e.g., when creating an invoice, or doing any update that involves multiple tables. It works about the way you'd expect it to but is not really necessary for the vast majority of operations in an Access application.

Perhaps one of the issues here (particularly in light of the first question) is that you may not quite grasp that Access is designed for creating apps with data bound to the forms. "Transactions" is a topic of great importance for unbound and stateless apps (e.g., browser-based), but for data bound apps, the editing and saving all happens transparently.

For certain kinds of operations this can be problematic, and occasionally it's appropriate to edit data in Access with unbound forms. But that's very seldom the case, in my experience. It's not that I don't use unbound forms -- I use lots of them for dialogs and the like -- it's just that my apps don't edit data tables with unbound forms. With almost no exceptions, all my apps edit data with bound forms.

Now, unbound forms are actually fairly easy to implement in Access (particularly if you name your editing controls the same as the underlying fields), but going with unbound data editing forms is really missing the point of using Access, which is that the binding is all done for you. And the main drawback of going unbound is that you lose all the record-level form events, such as OnInsert, BeforeUpdate and so forth.

Q3. Can we work on forms, queries etc. while they are being used? How can we "program" without being in the way of the users?

This is one of the questions that's been well-addressed. All multi-user or replicated Access apps should be split, and most single-user apps should be, too. It's good design and also makes the apps more stable, as only the data tables end up being opened by more than one user at a time.

Q4. Which settings in MS Access have an influence on how things are handled?

"Things?" What things?

Q5. Our background is mostly in Oracle, where is Access different in handling multiple users? Is there such thing as "isolation levels" in Access?

I don't know anything specifically about Oracle (none of my clients could afford it even if they wanted to), but asking for a comparison of Access and Oracle betrays a fundamental misunderstanding somewhere along the line.

Access is an application development tool.

Oracle is an industrial strength database server.

Apples and oranges.

Now, of course, Access ships with a default database engine, originally called Jet and now revised and renamed ACE, but there are many levels at which Access the development platform can be entirely decoupled from Jet/ACE, the default database engine.

In this case, you've chosen to use a Jet/ACE back end, which will likely be just fine for small user populations, i.e., under 25. Jet/ACE can also be fine up to 50 or 100, particularly when only a few of the simultaneous users have write permission. While the 255-user limit in Jet/ACE includes both read-only and write users, it's the number of write users that really controls how many simultaneous users you can support, and in your case, you've got an app with mostly read-only users, so it oughtn't be terribly difficult to engineer a good app that has no problems with the back end.

Basically, I think your Oracle background is likely leading you to misunderstand how to develop in Access, where the expected approach is to bind your forms to recordsources that are updated without any need to write code. Now, for efficiency's sake it's a good idea to bind your forms to subsets of records, rather than to whole tables, but even with an entire table in the recordsource behind a data editing form, Access is going to be fairly efficient in editing Jet/ACE tables (the old myth about pulling the whole table across the wire is still out there) as long your data tables are efficiently indexed.

Record locking is something you mostly shouldn't have any cause to worry about, and one of the reasons for that is because of bound editing, where the form knows what's going on in the back end at all times (well, at intervals about a second apart, the default refresh interval). That is, it's not like a web page where you retrieve a copy of the data and then post your edits back to the server in a transaction completely unconnected to the original data retrieval operation. In a bound environment like Access, the locking file on the back-end data file is always going to be keeping track of the fact that someone has the record open for editing. This prevents a user's edits from stomping on someone else's edits, because Access knows the state and informs the user. This all happens without any coding on the part of the developer and is one of the great advantages of the bound editing model (aside from not having to write code to post the edits).

For all those who are experienced database programmers familiar with other platforms who are coming to Access for the first time, I strongly suggest using Access like an end user. Try out all the point and click features. Run the form and report wizards and check out the results that they produce. I can't vouch for all of them as demonstrating good practices, but they definitely demonstrate the default assumptions behind the way Access is intended to be used.

If you find yourself writing a lot of code, then you're likely missing the point of Access.

Can angularjs routes have optional parameter values?

Please see @jlareau answer here:

You can use a function to generate the template string:

var app = angular.module('app',[]);

    function($routeProvider) {
            when('/', {templateUrl:'/home'}).
                    templateUrl: function(params){ return '/users/view/' + params.user_id;   }

Connect to Active Directory via LDAP

DC is your domain. If you want to connect to the domain than your dc's are: DC=example,DC=com

You actually don't need any hostname or ip address of your domain controller (There could be plenty of them).

Just imagine that you're connecting to the domain itself. So for connecting to the domain you can simply write

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://");

And you're done.

You can also specify a user and a password used to connect:

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://", "username", "password");

Also be sure to always write LDAP in upper case. I had some trouble and strange exceptions until I read somewhere that I should try to write it in upper case and that solved my problems.

The directoryEntry.Path Property allows you to dive deeper into your domain. So if you want to search a user in a specific OU (Organizational Unit) you can set it there.

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://");
directoryEntry.Path = "LDAP://OU=Specific Users,OU=All Users,OU=Users,DC=example,DC=com";

This would match the following AD hierarchy:

  • com
    • example
      • Users
        • All Users
          • Specific Users

Simply write the hierarchy from deepest to highest.

Now you can do plenty of things

For example search a user by account name and get the user's surname:

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://");
DirectorySearcher searcher = new DirectorySearcher(directoryEntry) {
    PageSize = int.MaxValue,
    Filter = "(&(objectCategory=person)(objectClass=user)(sAMAccountName=AnAccountName))"


var result = searcher.FindOne();

if (result == null) {
    return; // Or whatever you need to do in this case

string surname;

if (result.Properties.Contains("sn")) {
    surname = result.Properties["sn"][0].ToString();

Removing multiple keys from a dictionary safely

If you also need to retrieve the values for the keys you are removing, this would be a pretty good way to do it:

values_removed = [d.pop(k, None) for k in entities_to_remove]

You could of course still do this just for the removal of the keys from d, but you would be unnecessarily creating the list of values with the list comprehension. It is also a little unclear to use a list comprehension just for the function's side effect.

Load image from resources area of project in C#

this.toolStrip1 = new System.Windows.Forms.ToolStrip();
this.toolStrip1.Location = new System.Drawing.Point(0, 0);
this.toolStrip1.Name = "toolStrip1";
this.toolStrip1.Size = new System.Drawing.Size(444, 25);
this.toolStrip1.TabIndex = 0;
this.toolStrip1.Text = "toolStrip1";
object O = global::WindowsFormsApplication1.Properties.Resources.ResourceManager.GetObject("best_robust_ghost");

ToolStripButton btn = new ToolStripButton("m1");
btn.DisplayStyle = ToolStripItemDisplayStyle.Image;
btn.Image = (Image)O;

SQL providerName in web.config


Error Code: 1005. Can't create table '...' (errno: 150)

Error Code: 1005 -- there is a wrong primary key reference in your code

Usually it's due to a referenced foreign key field that does not exist. It might be you have a typo mistake, or check case it should be same, or there's a field-type mismatch. Foreign key-linked fields must match definitions exactly.

Some known causes may be:

  1. The two key fields type and/or size doesn’t match exactly. For example, if one is INT(10) the key field needs to be INT(10) as well and not INT(11) or TINYINT. You may want to confirm the field size using SHOW CREATE TABLE because Query Browser will sometimes visually show just INTEGER for both INT(10) and INT(11). You should also check that one is not SIGNED and the other is UNSIGNED. They both need to be exactly the same.
  2. One of the key field that you are trying to reference does not have an index and/or is not a primary key. If one of the fields in the relationship is not a primary key, you must create an index for that field.
  3. The foreign key name is a duplicate of an already existing key. Check that the name of your foreign key is unique within your database. Just add a few random characters to the end of your key name to test for this.
  4. One or both of your tables is a MyISAM table. In order to use foreign keys, the tables must both be InnoDB. (Actually, if both tables are MyISAM then you won’t get an error message - it just won’t create the key.) In Query Browser, you can specify the table type.
  5. You have specified a cascade ON DELETE SET NULL, but the relevant key field is set to NOT NULL. You can fix this by either changing your cascade or setting the field to allow NULL values.
  6. Make sure that the Charset and Collate options are the same both at the table level as well as individual field level for the key columns.
  7. You have a default value (that is, default=0) on your foreign key column
  8. One of the fields in the relationship is part of a combination (composite) key and does not have its own individual index. Even though the field has an index as part of the composite key, you must create a separate index for only that key field in order to use it in a constraint.
  9. You have a syntax error in your ALTER statement or you have mistyped one of the field names in the relationship
  10. The name of your foreign key exceeds the maximum length of 64 characters.

For more details, refer to: MySQL Error Number 1005 Can’t create table

Align a div to center

Use "spacer" divs to surround the div you want to center. Works best with a fluid design. Be sure to give the spacers height, or else they will not work.

dvi.row div{float=left;}
div.spacer{width=10%; height=10px;}

<div class="row">
<div class="spacer"></div>
<div id="content">...</div>
<div class="spacer"></div>

PHP: Show yes/no confirmation dialog

Try this:

    <a onclick="return confirm(\'Are you sure?\');" href="'.base_url('category/delete_category/'.$row->category_id).'" class="btn btn-danger btn-sm"><i class="fa fa-trash"></i> Delete Coupon</a>

Counting the number of option tags in a select tag in jQuery

Another approach that can be useful.


Uninstall old versions of Ruby gems

For removing older versions of all installed gems, following 2 commands are useful:

 gem cleanup --dryrun

Above command will preview what gems are going to be removed.

 gem cleanup

Above command will actually remove them.

How to disable Excel's automatic cell reference change after copy/paste?


  1. Put Excel in formula view mode. The easiest way to do this is to press Ctrl+` (that character is a "backwards apostrophe," and is usually on the same key that has the ~ (tilde).
  2. Select the range to copy.
  3. Press Ctrl+C
  4. Start Windows Notepad
  5. Press Ctrl+V to past the copied data into Notepad
  6. In Notepad, press Ctrl+A followed by Ctrl+C to copy the text
  7. Activate Excel and activate the upper left cell where you want to paste the formulas. And, make sure that the sheet you are copying to is in formula view mode.
  8. Press Ctrl+V to paste.
  9. Press Ctrl+` to toggle out of formula view mode.

Note: If the paste operation back to Excel doesn't work correctly, chances are that you've used Excel's Text-to-Columns feature recently, and Excel is trying to be helpful by remembering how you last parsed your data. You need to fire up the Convert Text to Columns Wizard. Choose the Delimited option and click Next. Clear all of the Delimiter option checkmarks except Tab.

Or, from

If you're a VBA programmer, you can simply execute the following code: 
With Sheets("Sheet1")
 .Range("A11:D20").Formula = .Range("A1:D10").Formula
End With

How do I set up NSZombieEnabled in Xcode 4?

In Xcode 4.2

  • Project Name/Edit Scheme/Diagnostics/
  • Enable Zombie Objects check box
  • You're done

How to convert QString to int?

Use .toInt() for int .toFloat() for float and .toDouble() for double


Angular 2 - Setting selected value on dropdown list

This Example solution is for reactive form

 <select formControlName="preferredBankAccountId" class="form-control">
                <option *ngFor="let item of societyAccountDtos" [value]="item.societyAccountId" >

In the Component:

        preferredBankAccountId:  object_id_to_be_pre_selected

You can also give this value where you initialize your formGroup or later,depending on your requirement.

You can do this by using [(ngModel)] binding also where you don't have to initialize your formControl.

Example with [(ngModel)] binding

 <select [(ngModel)]="matchedCity" formControlName="city" class="form-control input-sm">
                  <option *ngFor="let city of cities" [ngValue]="city">{{city.cityName}}</option>

Here, matchedCity is one of object within cities.

How to return first 5 objects of Array in Swift?

Swift 4 with saving array types

extension Array {
    func take(_ elementsCount: Int) -> [Element] {
        let min = Swift.min(elementsCount, count)
        return Array(self[0..<min])

Detect Android phone via Javascript / jQuery

I think Michal's answer is the best, but we can take it a step further and dynamically load an Android CSS as per the original question:

var isAndroid = /(android)/i.test(navigator.userAgent);
if (isAndroid) {
    var css = document.createElement("link");
    css.setAttribute("rel", "stylesheet");
    css.setAttribute("type", "text/css");
    css.setAttribute("href", "/css/android.css");

How to check if an integer is within a range of numbers in PHP?

$ranges = [
    1 => [
        'min_range' => 0.01,
        'max_range' => 199.99
    2 => [
        'min_range' => 200.00,

   foreach( $ranges as $value => $range ){
        if( filter_var( $cartTotal, FILTER_VALIDATE_FLOAT, [ 'options' => $range ] ) ){
            return $value;

How to do what head, tail, more, less, sed do in Powershell?

If you need to query large (or small) log files on Windows, the best tool I have found is Microsoft's free Log Parser 2.2. You can call it from PowerShell if you want and it will do all the heavy lifting for you, and very fast too.

What is the meaning of git reset --hard origin/master?

In newer version of git (2.23+) you can use:

git switch -C master origin/master

-C is same as --force-create. Related Reference Docs

Converting Swagger specification JSON to HTML documentation

Try to use redoc-cli.

I was using bootprint-openapi by which I was generating a bunch of files (bundle.js,, index.html, main.css and and then you can convert it into a single .html file using html-inline to generate a simple index.html file.

Then I found redoc-cli very easy to to use and output is really-2 awesome, a single and beautiful index.html file.


npm install -g redoc-cli


redoc-cli bundle -o index.html swagger.json

Center content vertically on Vuetify

Still surprised that no one proposed the shortest solution with align-center justify-center to center content vertically and horizontally. Check this CodeSandbox and code below:

<v-container fluid fill-height>
  <v-layout align-center justify-center>
      <!-- Some HTML elements... -->

jQuery Mobile how to check if button is disabled?

Faced with the same issue when trying to check if a button is disabled. I've tried a variety of approaches, such as btn.disabled, .is(':disabled'), .attr('disabled'), .prop('disabled'). But no one works for me.

Some, for example .disabled or .is(':disabled') returned undefined and other like .attr('disabled') returned the wrong result - false when the button was actually disabled.

But only one technique works for me: .is('[disabled]') (with square brackets).

So to determine if a button is disabled try this:


How can I initialize a MySQL database with schema in a Docker container?

For the ones not wanting to create an entrypoint script like me, you actually can start mysqld at build-time and then execute the mysql commands in your Dockerfile like so:

RUN mysqld_safe & until mysqladmin ping; do sleep 1; done && \
    mysql -uroot -e "CREATE DATABASE somedb;" && \
    mysql -uroot -e "CREATE USER 'someuser'@'localhost' IDENTIFIED BY 'somepassword';" && \
    mysql -uroot -e "GRANT ALL PRIVILEGES ON somedb.* TO 'someuser'@'localhost';"

The key here is to send mysqld_safe to background with the single & sign.

How to get UTF-8 working in Java webapps?

Some time you can solve problem through MySQL Administrator wizard. In

Startup variables > Advanced >

and set Def. char Set:utf8

Maybe this config need restart MySQL.

How do you turn a Mongoose document into a plain object?

A better way of tackling an issue like this is using doc.toObject() like this

doc.toObject({ getters: true })

other options include:

  • getters: apply all getters (path and virtual getters)
  • virtuals: apply virtual getters (can override getters option)
  • minimize: remove empty objects (defaults to true)
  • transform: a transform function to apply to the resulting document before returning
  • depopulate: depopulate any populated paths, replacing them with their original refs (defaults to false)
  • versionKey: whether to include the version key (defaults to true)

so for example you can say

Model.findOne().exec((err, doc) => {
   if (!err) {
      doc.toObject({ getters: true })
      console.log('doc _id:', doc._id)

and now it will work.

For reference, see:

How do I dynamically set HTML5 data- attributes using react?

Note - if you want to pass a data attribute to a React Component, you need to handle them a little differently than other props.

2 options

Don't use camel case

<Option data-img-src='value' ... />

And then in the component, because of the dashes, you need to refer to the prop in quotes.

// @flow
class Option extends React.Component {

  props: {
    'data-img-src': string

And when you refer to it later, you don't use the dot syntax

  render () {
    return (
      <option data-img-src={this.props['data-img-src']} >...</option>

Or use camel case

<Option dataImgSrc='value' ... />

And then in the component, you need to convert.

// @flow
class Option extends React.Component {

  props: {
    dataImgSrc: string

And when you refer to it later, you don't use the dot syntax

  render () {
    return (
      <option data-img-src={this.props.dataImgSrc} >...</option>

Mainly just realize data- attributes and aria- attributes are treated specially. You are allowed to use hyphens in the attribute name in those two cases.

How can I count the numbers of rows that a MySQL query returned?

If you're fetching data using Wordpress, then you can access the number of rows returned using $wpdb->num_rows:

$wpdb->get_results( $wpdb->prepare('select * from mytable where foo = %s', $searchstring));
echo $wpdb->num_rows;

If you want a specific count based on a mysql count query then you do this:

$numrows = $wpdb->get_var($wpdb->prepare('SELECT COUNT(*) FROM mytable where foo = %s', $searchstring );
echo $numrows;

If you're running updates or deletes then the count of rows affected is returned directly from the function call:

$numrowsaffected = $wpdb->query($wpdb->prepare(
   'update mytable set val=%s where myid = %d', $valuetoupdate, $myid));

This applies also to $wpdb->update and $wpdb->delete.

CSS to keep element at "fixed" position on screen

position: fixed;

Will make this happen.

It handles like position:absolute; with the exception that it will scroll with the window as the user scrolls down the content.

Error 6 (net::ERR_FILE_NOT_FOUND): The files c or directory could not be found

I have solved this issue as follows:

removed from chrome extension and install ext again. It will work ISA

Intellij Idea: Importing Gradle project - getting JAVA_HOME not defined yet

If you'd like to have your JAVA_HOME recognised by intellij, you can do one of these:

  • Start your intellij from terminal /Applications/IntelliJ IDEA (this will pick your bash env variables)
  • Add login env variable by executing: launchctl setenv JAVA_HOME "/Library/Java/JavaVirtualMachines/jdk1.8.0_60.jdk/Contents/Home"

As others have answered you can ignore JAVA_HOME by setting up SDK in project structure.

No Title Bar Android Theme

To Hide the Action Bar add the below code in Values/Styles

<style name="CustomActivityThemeNoActionBar" parent="@android:style/Theme.Holo.Light">
    <item name="android:windowActionBar">false</item>
    <item name="android:windowNoTitle">true</item>

Then in your AndroidManifest.xml file add the below code in the required activity


Could not find the main class, program will exit

I tried to start SQUirrel 3.1 but I received a message stating "Could not find the main class Files\Rational\ClearQuest\cqjni.jar" I noticed that C:\Program Files\Rational\ClearQuest\cqjni.jar is in my existing classpath as defined by the Windows environment variable, CLASSPATH.

SQUirrel doesn't need my existing classpath, so I updated the SQUirrel bat file, squirrel-sql.bat.



It no longer appends my existing classpath to its classpath and runs fine.

Send file via cURL from form POST in PHP

we can upload image file by curl request by converting it base64 string.So in post we will send file string and then covert this in an image.

function covertImageInBase64()
    var imageFile = document.getElementById("imageFile").files;
    if (imageFile.length > 0)
        var imageFileUpload = imageFile[0];
        var readFile = new FileReader();
        readFile.onload = function(fileLoadedEvent) 
            var base64image = document.getElementById("image");
            base64image.value =;

then send it in curl request

    $ch = curl_init();
    curl_setopt($ch,CURLOPT_URL, $curlUrl);
    curl_setopt($ch,CURLOPT_POST, 1);
    curl_setopt($ch,CURLOPT_POSTFIELDS, 'image='.$_POST['image']);
    $result = curl_exec($ch);

see here

Breaking out of nested loops

If you're able to extract the loop code into a function, a return statement can be used to exit the outermost loop at any time.

def foo():
    for x in range(10):
        for y in range(10):
            if x*y > 50:

If it's hard to extract that function you could use an inner function, as @bjd2385 suggests, e.g.

def your_outer_func():
    def inner_func():
        for x in range(10):
            for y in range(10):
                if x*y > 50:

How to quickly clear a JavaScript Object?

Something new to think about looking forward to Object.observe in ES7 and with data-binding in general. Consider:

var foo={
   name: "hello"

Object.observe(foo, function(){alert('modified');}); // bind to foo

foo={}; // You are no longer bound to foo but to an orphaned version of it"there"; // This change will be missed by Object.observe()

So under that circumstance #2 can be the best choice.

Rails 4: how to use $(document).ready() with turbo-links

You have to use:

document.addEventListener("turbolinks:load", function() {
  // your code here

from turbolinks doc.

ValueError: unsupported pickle protocol: 3, python2 pickle can not load the file dumped by python 3 pickle?

Pickle uses different protocols to convert your data to a binary stream.

You must specify in python 3 a protocol lower than 3 in order to be able to load the data in python 2. You can specify the protocol parameter when invoking pickle.dump.

Linq select object from list depending on objects attribute

if a.Correct is a bool flag for the correct answer then you need.

Answer answer = Answers.Single(a => a.Correct);

How to open specific tab of bootstrap nav tabs on click of a particuler link using jQuery?

Applying a selector from the .nav-tabs seems to be working


<ul class="nav nav-tabs">
    <li><a href="#aaa" data-toggle="tab">AAA</a></li>
    <li><a href="#bbb" data-toggle="tab">BBB</a></li>
    <li><a href="#ccc" data-toggle="tab">CCC</a></li>
<div class="tab-content" id="tabs">
    <div class="tab-pane" id="aaa">...Content...</div>
    <div class="tab-pane" id="bbb">...Content...</div>
    <div class="tab-pane" id="ccc">...Content...</div>

Script is


function activaTab(tab){
  $('.nav-tabs a[href="#' + tab + '"]').tab('show');

How can I make a time delay in Python?

While everyone else has suggested the de facto time module, I thought I'd share a different method using matplotlib's pyplot function, pause.

An example

from matplotlib import pyplot as plt
plt.pause(5)    # Pauses the program for 5 seconds

Typically this is used to prevent the plot from disappearing as soon as it is plotted or to make crude animations.

This would save you an import if you already have matplotlib imported.

How to connect to a secure website using SSL in Java with a pkcs12 file?

It appears that you are extracting you certificate from the PKCS #12 key store and creating a new Java key store (with type "JKS"). You don't strictly have to provide a trust store password (although using one allows you to test the integrity of your root certificates).

So, try your program with only the following SSL properties set. The list shown in your question is over-specified and may be causing problems.

System.setProperty("", "myTrustStore");
System.setProperty("", "changeit");

Also, using the PKCS #12 file directly as the trust store should work, as long as the CA certificate is detected as a "trusted" entry. But in that case, you'll have to specify the property as "PKCS12" too.

Try with these properties only. If you get the same error, I suspect your problem is not the key store. If it still occurs, post more of the stack trace in your question to narrow the problem down.

The new error, "the trustAnchors parameter must be non-empty," could be due to setting the property to a file that doesn't exist; if the file cannot be opened, an empty key store created, which would lead to this error.

What are the differences between .so and .dylib on osx?

Just an observation I just made while building naive code on OSX with cmake:


creates .so files


cmake ... -DBUILD_SHARED_LIBS=ON ...

creates .dynlib files.

Perhaps this helps anyone.

Assign a synthesizable initial value to a reg in Verilog

The other answers are all good. For Xilinx FPGA designs, it is best not to use global reset lines, and use initial blocks for reset conditions for most logic. Here is the white paper from Ken Chapman (Xilinx FPGA guru)

changing default x range in histogram matplotlib

plt.hist(hmag, 30, range=[6.5, 12.5], facecolor='gray', align='mid')

How can I use break or continue within for loop in Twig template?

This can be nearly done by setting a new variable as a flag to break iterating:

{% set break = false %}
{% for post in posts if not break %}
    <h2>{{ post.heading }}</h2>
    {% if == 10 %}
        {% set break = true %}
    {% endif %}
{% endfor %}

An uglier, but working example for continue:

{% set continue = false %}
{% for post in posts %}
    {% if == 10 %}
        {% set continue = true %}
    {% endif %}
    {% if not continue %}
        <h2>{{ post.heading }}</h2>
    {% endif %}
    {% if continue %}
        {% set continue = false %}
    {% endif %}
{% endfor %}

But there is no performance profit, only similar behaviour to the built-in break and continue statements like in flat PHP.

Is it wrong to place the <script> tag after the </body> tag?

It won't validate outside of the <body> or <head> tags. It also won't make much difference — unless you're doing DOM manipulations that could break IE before the body element is fully loaded — to putting it just before the closing </body>.

     <script type="text/javascript" src="theJs.js"></script>

C# SQL Server - Passing a list to a stored procedure

If you're using SQL Server 2008, there's a new featured called a User Defined Table Type. Here is an example of how to use it:

Create your User Defined Table Type:

CREATE TYPE [dbo].[StringList] AS TABLE(

Next you need to use it properly in your stored procedure:

CREATE PROCEDURE [dbo].[sp_UseStringList]
    @list StringList READONLY
    -- Just return the items we passed in
    SELECT l.Item FROM @list l;

Finally here's some sql to use it in c#:

using (var con = new SqlConnection(connstring))

    using (SqlCommand cmd = new SqlCommand("exec sp_UseStringList @list", con))
        using (var table = new DataTable()) {
          table.Columns.Add("Item", typeof(string));

          for (int i = 0; i < 10; i++)
            table.Rows.Add("Item " + i.ToString());

          var pList = new SqlParameter("@list", SqlDbType.Structured);
          pList.TypeName = "dbo.StringList";
          pList.Value = table;


          using (var dr = cmd.ExecuteReader())
            while (dr.Read())

To execute this from SSMS

DECLARE @list AS StringList

INSERT INTO @list VALUES ('Apple')
INSERT INTO @list VALUES ('Banana')
INSERT INTO @list VALUES ('Orange')

-- Alternatively, you can populate @list with an INSERT-SELECT
   SELECT Name FROM Fruits

EXEC sp_UseStringList @list

How to update gradle in android studio?

I can't comment yet.

Same as Kevin but with different UI step:

This may not be the exact answer for the OP, but is the answer to the Title of the question: How to Update Gradle in Android Studio (AS):

  • Get latest version supported by AS: (Currently 1.9, 1.10 is NOT supported by AS yet)
  • Install: Unzip to anywhere like near where AS is installed: C:\Users[username]\gradle-1.9\
  • Open AS: File->Settings->Build, Execution, Deployment->Build Tools-> Gradle->Service directory path: (Change to folder you set above) ->Click ok. Status on bottom should indicate it's busy & error should be fixed. Might have to restart AS

How to concatenate a std::string and an int?

#include <string>
#include <sstream>
using namespace std;
string concatenate(std::string const& name, int i)
    stringstream s;
    s << name << i;
    return s.str();

How do I find numeric columns in Pandas?

df.select_dtypes(exclude = ['object'])


df.select_dtypes(include= np.number)

or with new version of panda


How do I do logging in C# without using 3rd party libraries?

You can write directly to an event log. Check the following links:

And here's the sample from MSDN:

using System;
using System.Diagnostics;
using System.Threading;

class MySample{

    public static void Main(){

        // Create the source, if it does not already exist.
             //An event log source should not be created and immediately used.
             //There is a latency time to enable the source, it should be created
             //prior to executing the application that uses the source.
             //Execute this sample a second time to use the new source.
            EventLog.CreateEventSource("MySource", "MyNewLog");
            Console.WriteLine("Exiting, execute the application a second time to use the source.");
            // The source is created.  Exit the application to allow it to be registered.

        // Create an EventLog instance and assign its source.
        EventLog myLog = new EventLog();
        myLog.Source = "MySource";

        // Write an informational entry to the event log.    
        myLog.WriteEntry("Writing to event log.");


Running windows shell commands with python

Refactoring of @srini-beerge's answer which gets the output and the return code

import subprocess
def run_win_cmd(cmd):
    result = []
    process = subprocess.Popen(cmd,
    for line in process.stdout:
    errcode = process.returncode
    for line in result:
    if errcode is not None:
        raise Exception('cmd %s failed, see above for details', cmd)

iPhone and WireShark

The tcpdump tool is available under gnu.

You can use it instead of wireshark.

Adding default parameter value with type hint in Python

I recently saw this one-liner:

def foo(name: str, opts: dict=None) -> str:
    opts = {} if not opts else opts

java.lang.NoClassDefFoundError: org/json/JSONObject

Add json jar to your classpath

or use java -classpath json.jar ClassName

refer this

Sort dataGridView columns in C# ? (Windows Form)

There's a method on the DataGridView called "Sort":

this.dataGridView1.Sort(this.dataGridView1.Columns["Name"], ListSortDirection.Ascending);

This will programmatically sort your datagridview.

Eclipse C++ : "Program "g++" not found in PATH"

First Install MinGW or other C/C++ compiler as it's required by Eclipse C++.

Use as unbelievably the's version has malware attached.

Back to Eclipse.

Now in all those path settings that the Eclipse Help manual talks about INSTEAD of typing the path, Select Variables and


and do so for all instances which would ask for the compiler's path.

First would be to click Preferences of the whatever project and C/C++ General then Paths and Symbols and add the

**MINGW_HOME** to those paths of for the compiler.

Next simply add the home directory to the Build Variables under the C++/C Build

Build Variables Screen Capture

SQL where datetime column equals today's date?

Looks like you're using SQL Server, in which case GETDATE() or current_timestamp may help you. But you will have to ensure that the format of the date with which you are comparing the system dates matches (timezone, granularity etc.)


where convert(varchar(10), submission_date, 102) 
    = convert(varchar(10), getdate(), 102)

What values for checked and selected are false?

There are no values that will cause the checkbox to be unchecked. If the checked attribute exists, the checkbox will be checked regardless of what value you set it to.

<input type="checkbox" checked />_x000D_
<input type="checkbox" checked="" />_x000D_
<input type="checkbox" checked="checked" />_x000D_
<input type="checkbox" checked="unchecked" />_x000D_
<input type="checkbox" checked="true" />_x000D_
<input type="checkbox" checked="false" />_x000D_
<input type="checkbox" checked="on" />_x000D_
<input type="checkbox" checked="off" />_x000D_
<input type="checkbox" checked="1" />_x000D_
<input type="checkbox" checked="0" />_x000D_
<input type="checkbox" checked="yes" />_x000D_
<input type="checkbox" checked="no" />_x000D_
<input type="checkbox" checked="y" />_x000D_
<input type="checkbox" checked="n" />

Renders everything checked in all modern browsers (FF3.6, Chrome 10, IE8).

How to listen to the window scroll event in a VueJS component?

In my experience, using an event listener on scroll can create a lot of noise due to piping into that event stream, which can cause performance issues if you are executing a bulky handleScroll function.

I often use the technique shown here in the highest rated answer, but I add debounce on top of it, usually about 100ms yields good performance to UX ratio.

Here is an example using the top-rated answer with Lodash debounce added:

import debounce from 'lodash/debounce';

export default {
  methods: {
    handleScroll(event) {
      // Any code to be executed when the window is scrolled
      this.isUserScrolling = (window.scrollY > 0);
      console.log('calling handleScroll');

  created() {
    this.handleDebouncedScroll = debounce(this.handleScroll, 100);
    window.addEventListener('scroll', this.handleDebouncedScroll);

  beforeDestroy() {
    // I switched the example from `destroyed` to `beforeDestroy`
    // to exercise your mind a bit. This lifecycle method works too.
    window.removeEventListener('scroll', this.handleDebouncedScroll);

Try changing the value of 100 to 0 and 1000 so you can see the difference in how/when handleScroll is called.

BONUS: You can also accomplish this in an even more concise and reuseable manner with a library like vue-scroll. It is a great use case for you to learn about custom directives in Vue if you haven't seen those yet. Check out

This is also a great tutorial by Sarah Drasner in the Vue docs:

How to take keyboard input in JavaScript?

You should register an event handler on the window or any element that you want to observe keystrokes on, and use the standard key values instead of keyCode. This modified code from MDN will respond to keydown when the left, right, up, or down arrow keys are pressed:

window.addEventListener("keydown", function (event) {_x000D_
  if (event.defaultPrevented) {_x000D_
    return; // Do nothing if the event was already processed_x000D_
  switch (event.key) {_x000D_
    case "ArrowDown":_x000D_
      // code for "down arrow" key press._x000D_
    case "ArrowUp":_x000D_
      // code for "up arrow" key press._x000D_
    case "ArrowLeft":_x000D_
      // code for "left arrow" key press._x000D_
    case "ArrowRight":_x000D_
      // code for "right arrow" key press._x000D_
      return; // Quit when this doesn't handle the key event._x000D_
  // Cancel the default action to avoid it being handled twice_x000D_
}, true);_x000D_
// the last option dispatches the event to the listener first,_x000D_
// then dispatches event to window

jquery equivalent for JSON.stringify

There is no such functionality in jQuery. Use JSON.stringify or alternatively any jQuery plugin with similar functionality (e.g jquery-json).

Using Math.round to round to one decimal place?

If you need this and similar operations more often, it may be more convenient to find the right library instead of implementing it yourself.

Here are one-liners solving your question from Apache Commons Math using Precision, Colt using Functions, and Weka using Utils:

double value = 540.512 / 1978.8 * 100;
// Apache commons math
double rounded1 = Precision.round(value, 1);
double rounded2 = Precision.round(value, 1, BigDecimal.ROUND_HALF_UP);
// Colt
double rounded3 = Functions.round(0.1).apply(value)
// Weka
double rounded4 = Utils.roundDouble(value, 1)

Maven dependencies:




Multiple conditions in ngClass - Angular 4

you need object notation

<section [ngClass]="{'class1':condition1, 'class2': condition2, 'class3':condition3}" > 

ref: NgClass

C# MessageBox dialog result

Rather than using if statements might I suggest using a switch instead, I try to avoid using if statements when possible.

var result = MessageBox.Show(@"Do you want to save the changes?", "Confirmation", MessageBoxButtons.YesNoCancel);
switch (result)
    case DialogResult.Yes:
    case DialogResult.No:

How to restore to a different database in sql server?

Actually, there is no need to restore the database in native SQL Server terms, since you "want to fiddle with some data" and "browse through the data of that .bak file"

You can use ApexSQL Restore – a SQL Server tool that attaches both native and natively compressed SQL database backups and transaction log backups as live databases, accessible via SQL Server Management Studio, Visual Studio or any other third-party tool. It allows attaching single or multiple full, differential and transaction log backups

Moreover, I think that you can do the job while the tool is in fully functional trial mode (14 days)

Disclaimer: I work as a Product Support Engineer at ApexSQL

powerpoint loop a series of animation

Unfortunately you're probably done with the animation and presentation already. In the hopes this answer can help future questioners, however, this blog post has a walkthrough of steps that can loop a single slide as a sort of sub-presentation.

First, click Slide Show > Set Up Show.

Put a checkmark to Loop continuously until 'Esc'.

Click Ok. Now, Click Slide Show > Custom Shows. Click New.

Select the slide you are looping, click Add. Click Ok and Close.

Click on the slide you are looping. Click Slide Show > Slide Transition. Under Advance slide, put a checkmark to Automatically After. This will allow the slide to loop automatically. Do NOT Apply to all slides.

Right click on the thumbnail of the current slide, select Hide Slide.

Now, you will need to insert a new slide just before the slide you are looping. On the new slide, insert an action button. Set the hyperlink to the custom show you have created. Put a checkmark on "Show and Return"

This has worked for me.

Android: How to create a Dialog without a title?

dialog=new Dialog(YourActivity.this, 1);  // to make dialog box full screen with out title.