Programs & Examples On #Krl

KRL stands for Kinetic Rule Language. Use this tag for questions regarding KRL applications.

How does one create an InputStream from a String?

Java 7+

It's possible to take advantage of the StandardCharsets JDK class:

String str=...
InputStream is = new ByteArrayInputStream(StandardCharsets.UTF_16.encode(str).array());

Split and join C# string

Well, here is my "answer". It uses the fact that String.Split can be told hold many items it should split to (which I found lacking in the other answers):

string theString = "Some Very Large String Here";
var array = theString.Split(new [] { ' ' }, 2); // return at most 2 parts
// note: be sure to check it's not an empty array
string firstElem = array[0];
// note: be sure to check length first
string restOfArray = array[1];

This is very similar to the Substring method, just by a different means.

jQuery.parseJSON throws “Invalid JSON” error due to escaped single quote in JSON

According to the state machine diagram on the JSON website, only escaped double-quote characters are allowed, not single-quotes. Single quote characters do not need to be escaped:

http://www.json.org/string.gif


Update - More information for those that are interested:


Douglas Crockford does not specifically say why the JSON specification does not allow escaped single quotes within strings. However, during his discussion of JSON in Appendix E of JavaScript: The Good Parts, he writes:

JSON's design goals were to be minimal, portable, textual, and a subset of JavaScript. The less we need to agree on in order to interoperate, the more easily we can interoperate.

So perhaps he decided to only allow strings to be defined using double-quotes since this is one less rule that all JSON implementations must agree on. As a result, it is impossible for a single quote character within a string to accidentally terminate the string, because by definition a string can only be terminated by a double-quote character. Hence there is no need to allow escaping of a single quote character in the formal specification.


Digging a little bit deeper, Crockford's org.json implementation of JSON for Java is more permissible and does allow single quote characters:

The texts produced by the toString methods strictly conform to the JSON syntax rules. The constructors are more forgiving in the texts they will accept:

...

  • Strings may be quoted with ' (single quote).

This is confirmed by the JSONTokener source code. The nextString method accepts escaped single quote characters and treats them just like double-quote characters:

public String nextString(char quote) throws JSONException {
    char c;
    StringBuffer sb = new StringBuffer();
    for (;;) {
        c = next();
        switch (c) {

        ...

        case '\\':
            c = this.next();
            switch (c) {

            ...

            case '"':
            case '\'':
            case '\\':
            case '/':
                sb.append(c);
                break;
        ...

At the top of the method is an informative comment:

The formal JSON format does not allow strings in single quotes, but an implementation is allowed to accept them.

So some implementations will accept single quotes - but you should not rely on this. Many popular implementations are quite restrictive in this regard and will reject JSON that contains single quoted strings and/or escaped single quotes.


Finally to tie this back to the original question, jQuery.parseJSON first attempts to use the browser's native JSON parser or a loaded library such as json2.js where applicable (which on a side note is the library the jQuery logic is based on if JSON is not defined). Thus jQuery can only be as permissive as that underlying implementation:

parseJSON: function( data ) {
    ...

    // Attempt to parse using the native JSON parser first
    if ( window.JSON && window.JSON.parse ) {
        return window.JSON.parse( data );
    }

    ...

    jQuery.error( "Invalid JSON: " + data );
},

As far as I know these implementations only adhere to the official JSON specification and do not accept single quotes, hence neither does jQuery.

Request Permission for Camera and Library in iOS 10 - Info.plist

Swift 5 The easiest way to add permissions without having to do it programatically, is to open your info.plist file and select the + next to Information Property list. Scroll through the drop down list to the Privacy options and select Privacy Camera Usage Description for accessing camera, or Privacy Photo Library Usage Description for accessing the Photo Library. Fill in the String value on the right after you've made your selection, to include the text you would like displayed to your user when the alert pop up asks for permissions. Camera/Photo Library permission

Running Composer returns: "Could not open input file: composer.phar"

This worked for me:

composer install

Without

php composer install

javascript create empty array of a given size

In 2018 and thenceforth we shall use [...Array(500)] to that end.

Converting Float to Dollars and Cents

you said that:

`mony = float(1234.5)
print(money)      #output is 1234.5
'${:,.2f}'.format(money)
print(money)

did not work.... Have you coded exactly that way? This should work (see the little difference):

money = float(1234.5)      #next you used format without printing, nor affecting value of "money"
amountAsFormattedString = '${:,.2f}'.format(money)
print( amountAsFormattedString )

How to unset (remove) a collection element after fetching it?

Or you can use reject method

$newColection = $collection->reject(function($element) {
    return $item->selected != true;
});

or pull method

$selected = []; 
foreach ($collection as $key => $item) {
      if ($item->selected == true) {
          $selected[] = $collection->pull($key);
      }
}

'cl' is not recognized as an internal or external command,

For me, this was related to the scenario described by Smi, with the difference being that vcvarsall.bat itself was failing due to an invalid path.

This was cause by line-breaks within the path, which meant vcvarsall.bat couldn't find the common tools directory for some reason.

Making a request to a RESTful API using python

Using requests:

import requests
url = 'http://ES_search_demo.com/document/record/_search?pretty=true'
data = '''{
  "query": {
    "bool": {
      "must": [
        {
          "text": {
            "record.document": "SOME_JOURNAL"
          }
        },
        {
          "text": {
            "record.articleTitle": "farmers"
          }
        }
      ],
      "must_not": [],
      "should": []
    }
  },
  "from": 0,
  "size": 50,
  "sort": [],
  "facets": {}
}'''
response = requests.post(url, data=data)

Depending on what kind of response your API returns, you will then probably want to look at response.text or response.json() (or possibly inspect response.status_code first). See the quickstart docs here, especially this section.

Getting the last n elements of a vector. Is there a better way than using the length() function?

I just add here something related. I was wanted to access a vector with backend indices, ie writting something like tail(x, i) but to return x[length(x) - i + 1] and not the whole tail.

Following commentaries I benchmarked two solutions:

accessRevTail <- function(x, n) {
    tail(x,n)[1]
}

accessRevLen <- function(x, n) {
  x[length(x) - n + 1]
}

microbenchmark::microbenchmark(accessRevLen(1:100, 87), accessRevTail(1:100, 87))
Unit: microseconds
                     expr    min      lq     mean median      uq     max neval
  accessRevLen(1:100, 87)  1.860  2.3775  2.84976  2.803  3.2740   6.755   100
 accessRevTail(1:100, 87) 22.214 23.5295 28.54027 25.112 28.4705 110.833   100

So it appears in this case that even for small vectors, tail is very slow comparing to direct access

get current url in twig template?

{{ path(app.request.attributes.get('_route'),
     app.request.attributes.get('_route_params')) }}

If you want to read it into a view variable:

{% set currentPath = path(app.request.attributes.get('_route'),
                       app.request.attributes.get('_route_params')) %}

The app global view variable contains all sorts of useful shortcuts, such as app.session and app.security.token.user, that reference the services you might use in a controller.

Transpose a range in VBA

This gets you X and X' as variant arrays you can pass to another function.

Dim X() As Variant
Dim XT() As Variant
X = ActiveSheet.Range("InRng").Value2
XT = Application.Transpose(X)

To have the transposed values as a range, you have to pass it via a worksheet as in this answer. Without seeing how your covariance function works it's hard to see what you need.

Using ng-click vs bind within link function of Angular Directive

In this case, no need for a directive. This does the job :

<button ng-click="count = count + 1" ng-init="count=0">
  Increment
</button>
<span>
  count: {{count}}
</span>

Source: https://docs.angularjs.org/api/ng/directive/ngClick

Update a dataframe in pandas while iterating row by row

Increment the MAX number from a column. For Example :

df1 = [sort_ID, Column1,Column2]
print(df1)

My output :

Sort_ID Column1 Column2
12         a    e
45         b    f
65         c    g
78         d    h

MAX = df1['Sort_ID'].max() #This returns my Max Number 

Now , I need to create a column in df2 and fill the column values which increments the MAX .

Sort_ID Column1 Column2
79      a1       e1
80      b1       f1
81      c1       g1
82      d1       h1

Note : df2 will initially contain only the Column1 and Column2 . we need the Sortid column to be created and incremental of the MAX from df1 .

Exercises to improve my Java programming skills

I highly recommend reading the book 'Effective Java' from Joshua Bloch.

How to set java_home on Windows 7?

This is the official solution for setting the Java environment from www.java.com - here.

There are solutions for Windows 7, Windows Vista, Windows XP, Linux/Solaris and other shells.


Example

Windows 7

  1. Select Computer from the Start menu
  2. Choose System Properties from the context menu
  3. Click Advanced system settings -> Advanced tab
  4. Click on Environment Variables, under System Variables, find PATH, and click on it.
  5. In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value.
  6. Reopen Command prompt window, and run your Java code.

How to prevent scanf causing a buffer overflow in C?

Directly using scanf(3) and its variants poses a number of problems. Typically, users and non-interactive use cases are defined in terms of lines of input. It's rare to see a case where, if enough objects are not found, more lines will solve the problem, yet that's the default mode for scanf. (If a user didn't know to enter a number on the first line, a second and third line will probably not help.)

At least if you fgets(3) you know how many input lines your program will need, and you won't have any buffer overflows...

How do I get the logfile from an Android device?

A simple way is to make your own log collector methods or even just an existing log collector app from the market.

For my apps I made a report functionality which sends the logs to my email (or even to another place - once you get the log you can do whether you want with it).

Here is a simple example about how to get the log file from a device:

Missing .map resource?

I had similar expirience like yours. I have Denwer server. When I loaded my http://new.new local site without using via script src jquery.min.js file at index.php in Chrome I got error 500 jquery.min.map in console. I resolved this problem simply - I disabled extension Wunderlist in Chrome and voila - I never see this error more. Although, No, I found this error again - when Wunderlist have been on again. So, check your extensions and try to disable all of them or some of them or one by one. Good luck!

WebApi's {"message":"an error has occurred"} on IIS7, not in IIS Express

None of the other answers worked for me.

This did: (in Startup.cs)

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        var config = new HttpConfiguration();

        WebApiConfig.Register(config);

        // Here: 
        config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;
    }
}

(or you can put it in WebApiConfig.cs):

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        // Web API routes
        config.MapHttpAttributeRoutes();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{action}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        // Here: 
        config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;
    }
}

What is [Serializable] and when should I use it?

Here is short example of how serialization works. I was also learning about the same and I found two links useful. What Serialization is and how it can be done in .NET.

A sample program explaining serialization

If you don't understand the above program a much simple program with explanation is given here.

WSDL/SOAP Test With soapui

You can try opening the wsdl in web browser and saving with .wsdl extension. And set the WSDL in SOAP UI project to this .wsdl file. This really works.

fill an array in C#

Say you want to fill with number 13.

int[] myarr = Enumerable.Range(0, 10).Select(n => 13).ToArray();

or

List<int> myarr = Enumerable.Range(0,10).Select(n => 13).ToList();

if you prefer a list.

Using Auto Layout in UITableView for dynamic cell layouts & variable row heights

An important enough gotcha I just ran into to post as an answer.

@smileyborg's answer is mostly correct. However, if you have any code in the layoutSubviews method of your custom cell class, for instance setting the preferredMaxLayoutWidth, then it won't be run with this code:

[cell.contentView setNeedsLayout];
[cell.contentView layoutIfNeeded];

It confounded me for awhile. Then I realized it's because those are only triggering layoutSubviews on the contentView, not the cell itself.

My working code looks like this:

TCAnswerDetailAppSummaryCell *cell = [self.tableView dequeueReusableCellWithIdentifier:@"TCAnswerDetailAppSummaryCell"];
[cell configureWithThirdPartyObject:self.app];
[cell layoutIfNeeded];
CGFloat height = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
return height;

Note that if you are creating a new cell, I'm pretty sure you don't need to call setNeedsLayout as it should already be set. In cases where you save a reference to a cell, you should probably call it. Either way it shouldn't hurt anything.

Another tip if you are using cell subclasses where you are setting things like preferredMaxLayoutWidth. As @smileyborg mentions, "your table view cell hasn't yet had its width fixed to the table view's width". This is true, and trouble if you are doing your work in your subclass and not in the view controller. However you can simply set the cell frame at this point using the table width:

For instance in the calculation for height:

self.summaryCell = [self.tableView dequeueReusableCellWithIdentifier:@"TCAnswerDetailDefaultSummaryCell"];
CGRect oldFrame = self.summaryCell.frame;
self.summaryCell.frame = CGRectMake(oldFrame.origin.x, oldFrame.origin.y, self.tableView.frame.size.width, oldFrame.size.height);

(I happen to cache this particular cell for re-use, but that's irrelevant).

How to obtain Telegram chat_id for a specific user?

I created a bot to get User or GroupChat id, just send the /my_id to telegram bot @get_id_bot.

It does not only work for user chat ID, but also for group chat ID.

To get group chat ID, first you have to add the bot to the group, then send /my_id in the group.

Here's the link to the bot.

How do I get bit-by-bit data from an integer value in C?

If you don't want any loops, you'll have to write it out:

#include <stdio.h>
#include <stdbool.h>

int main(void)
{
    int num = 7;

    #if 0
        bool arr[4] = { (num&1) ?true: false, (num&2) ?true: false, (num&4) ?true: false, (num&8) ?true: false };
    #else
        #define BTB(v,i) ((v) & (1u << (i))) ? true : false
        bool arr[4] = { BTB(num,0), BTB(num,1), BTB(num,2), BTB(num,3)};
        #undef BTB
    #endif

    printf("%d %d %d %d\n", arr[3], arr[2], arr[1], arr[0]);

    return 0;
}

As demonstrated here, this also works in an initializer.

How to bind inverse boolean properties in WPF?

.Net Core Solution

Handles null situation and does not throw an exception, but returns true if no value is presented; otherwise takes the inputted Boolean and reverses it.

public class BooleanToReverseConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
     => !(bool?) value ?? true;

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
     => !(value as bool?);
}

Xaml

IsEnabled="{Binding IsSuccess Converter={StaticResource BooleanToReverseConverter}}"

App.Xaml I like to put all my converter statics in the app.xaml file so I don't have to redeclare them throughout the windows/pages/controls of the project.

<Application.Resources>
    <converters:BooleanToReverseConverter x:Key="BooleanToReverseConverter"/>
    <local:FauxVM x:Key="VM" />
</Application.Resources>

To be clear converters: is the namespace to the actual class implementation (xmlns:converters="clr-namespace:ProvingGround.Converters").

How to convert NSNumber to NSString

In Swift 3.0

let number:NSNumber = 25
let strValue = String(describing: number as NSNumber)
print("As String => \(strValue)")

We can get the number value in String.

python's re: return True if string contains regex pattern

Here's a function that does what you want:

import re

def is_match(regex, text):
    pattern = re.compile(regex, text)
    return pattern.search(text) is not None

The regular expression search method returns an object on success and None if the pattern is not found in the string. With that in mind, we return True as long as the search gives us something back.

Examples:

>>> is_match('ba[rzd]', 'foobar')
True
>>> is_match('ba[zrd]', 'foobaz')
True
>>> is_match('ba[zrd]', 'foobad')
True
>>> is_match('ba[zrd]', 'foobam')
False

How to normalize a NumPy array to within a certain range?

audio /= np.max(np.abs(audio),axis=0)
image *= (255.0/image.max())

Using /= and *= allows you to eliminate an intermediate temporary array, thus saving some memory. Multiplication is less expensive than division, so

image *= 255.0/image.max()    # Uses 1 division and image.size multiplications

is marginally faster than

image /= image.max()/255.0    # Uses 1+image.size divisions

Since we are using basic numpy methods here, I think this is about as efficient a solution in numpy as can be.


In-place operations do not change the dtype of the container array. Since the desired normalized values are floats, the audio and image arrays need to have floating-point point dtype before the in-place operations are performed. If they are not already of floating-point dtype, you'll need to convert them using astype. For example,

image = image.astype('float64')

How to check if a column exists in Pandas

This will work:

if 'A' in df:

But for clarity, I'd probably write it as:

if 'A' in df.columns:

How to set 777 permission on a particular folder?

777 is a permission in Unix based system with full read/write/execute permission to owner, group and everyone.. in general we give this permission to assets which are not much needed to be hidden from public on a web server, for example images..

You said I am using windows 7. if that means that your web server is Windows based then you should login to that and right click the folder and set permissions to everyone and if you are on a windows client and server is unix/linux based then use some ftp software and in the parent directory right click and change the permission for the folder.

If you want permission to be set on sub-directories too then usually their is option to set permission recursively use that.

And, if you feel like doing it from command line the use putty and login to server and go to the parent directory includes and write the following command

chmod 0777 module_installation/

for recursive

chmod -R 0777 module_installation/

Hope this will help you

How do I ignore files in a directory in Git?

Both examples in the question are actually very bad examples that can lead to data loss!

My advice: never append /* to directories in .gitignore files, unless you have a good reason!

A good reason would be for example what Jefromi wrote: "if you intend to subsequently un-ignore something in the directory".

The reason why it otherwise shouldn't be done is that appending /* to directories does on the one hand work in the manner that it properly ignores all contents of the directory, but on the other hand it has a dangerous side effect:

If you execute git stash -u (to temporarily stash tracked and untracked files) or git clean -df (to delete untracked but keep ignored files) in your repository, all directories that are ignored with an appended /* will be irreversibly deleted!

Some background

I had to learn this the hard way. Somebody in my team was appending /* to some directories in our .gitignore. Over the time I had occasions where certain directories would suddenly disappear. Directories with gigabytes of local data needed by our application. Nobody could explain it and I always hat to re-download all data. After a while I got a notion that it might have to do with git stash. One day I wanted to clean my local repo (while keeping ignored files) and I was using git clean -df and again my data was gone. This time I had enough and investigated the issue. I finally figured that the reason is the appended /*.

I assume it can be explained somehow by the fact that directory/* does ignore all contents of the directory but not the directory itself. Thus it's neither considered tracked nor ignored when things get deleted. Even though git status and git status --ignored give a slightly different picture on it.

How to reproduce

Here is how to reproduce the behaviour. I'm currently using Git 2.8.4.

A directory called localdata/ with a dummy file in it (important.dat) will be created in a local git repository and the contents will be ignored by putting /localdata/* into the .gitignore file. When one of the two mentioned git commands is executed now, the directory will be (unexpectedly) lost.

mkdir test
cd test
git init
echo "/localdata/*" >.gitignore
git add .gitignore
git commit -m "Add .gitignore."
mkdir localdata
echo "Important data" >localdata/important.dat
touch untracked-file

If you do a git status --ignored here, you'll get:

On branch master
Untracked files:
  (use "git add <file>..." to include in what will be committed)

  untracked-file

Ignored files:
  (use "git add -f <file>..." to include in what will be committed)

  localdata/

Now either do

git stash -u
git stash pop

or

git clean -df

In both cases the allegedly ignored directory localdata will be gone!

Not sure if this can be considered a bug, but I guess it's at least a feature that nobody needs.

I'll report that to the git development list and see what they think about it.

How npm start runs a server on port 8000

npm start -- --port "port number"

Argparse optional positional arguments?

As an extension to @VinaySajip answer. There are additional nargs worth mentioning.

  1. parser.add_argument('dir', nargs=1, default=os.getcwd())

N (an integer). N arguments from the command line will be gathered together into a list

  1. parser.add_argument('dir', nargs='*', default=os.getcwd())

'*'. All command-line arguments present are gathered into a list. Note that it generally doesn't make much sense to have more than one positional argument with nargs='*', but multiple optional arguments with nargs='*' is possible.

  1. parser.add_argument('dir', nargs='+', default=os.getcwd())

'+'. Just like '*', all command-line args present are gathered into a list. Additionally, an error message will be generated if there wasn’t at least one command-line argument present.

  1. parser.add_argument('dir', nargs=argparse.REMAINDER, default=os.getcwd())

argparse.REMAINDER. All the remaining command-line arguments are gathered into a list. This is commonly useful for command line utilities that dispatch to other command line utilities

If the nargs keyword argument is not provided, the number of arguments consumed is determined by the action. Generally this means a single command-line argument will be consumed and a single item (not a list) will be produced.

Edit (copied from a comment by @Acumenus) nargs='?' The docs say: '?'. One argument will be consumed from the command line if possible and produced as a single item. If no command-line argument is present, the value from default will be produced.

What is lazy loading in Hibernate?

Lazy loading is a design pattern commonly used in computer programming to defer initialization of an object until the point at which it is needed. It can contribute to efficiency in the program's operation if properly and appropriately used

Wikipedia

Link of Lazy Loading from hibernate.org

Remove elements from collection while iterating

I would choose the second as you don't have to do a copy of the memory and the Iterator works faster. So you save memory and time.

How do I make the first letter of a string uppercase in JavaScript?

You can use a regular expression as below:

return string1.toLowerCase().replace(/^[a-zA-z]|\s(.)/ig, L => L.toUpperCase());

Convert Java String to sql.Timestamp

Have you tried using Timestamp.valueOf(String)? It looks like it should do almost exactly what you want - you just need to change the separator between your date and time to a space, and the ones between hours and minutes, and minutes and hours, to colons:

import java.sql.*;

public class Test {
    public static void main(String[] args) {
        String text = "2011-10-02 18:48:05.123456";
        Timestamp ts = Timestamp.valueOf(text);
        System.out.println(ts.getNanos());
    }
}

Assuming you've already validated the string length, this will convert to the right format:

static String convertSeparators(String input) {
    char[] chars = input.toCharArray();
    chars[10] = ' ';
    chars[13] = ':';
    chars[16] = ':';
    return new String(chars);
}

Alternatively, parse down to milliseconds by taking a substring and using Joda Time or SimpleDateFormat (I vastly prefer Joda Time, but your mileage may vary). Then take the remainder of the string as another string and parse it with Integer.parseInt. You can then combine the values pretty easily:

Date date = parseDateFromFirstPart();
int micros = parseJustLastThreeDigits();

Timestamp ts = new Timestamp(date.getTime());
ts.setNanos(ts.getNanos() + micros * 1000);

What is "loose coupling?" Please provide examples

In computer science there is another meaning for "loose coupling" that no one else has posted about here, so... Here goes - hopefully you'll give me some votes up so this isn't lost at the bottom of the heap! SURELY the subject of my answer belongs in any comprehensive answer to the question... To wit:

The term "Loose Coupling" first entered computing as a term used as an adjective regarding CPU architecture in a multi-CPU configuration. Its counterpart term is "tight coupling". Loose Coupling is when CPUs do not share many resources in common and Tight Coupling is when they do.

The term "system" can be confusing here so please parse the situation carefully.

Usually, but not always, multiple CPUs in a hardware configuration in which they exist within one system (as in individual "PC" boxes) would be tightly coupled. With the exception of some super-high-performance systems that have subsystems that actually share main memory across "systems", all divisible systems are loosely coupled.

The terms Tightly Coupled and Loosely Coupled were introduced before multi-threaded and multi-core CPUs were invented, so these terms may need some companions to fully articulate the situation today. And, indeed, today one may very well have a system that encompases both types in one overall system. Regarding current software systems, there are two common architectures, one of each variety, that are common enough these should be familliar.

First, since it was what the question was about, some examples of Loosely Coupled systems:

  • VaxClusters
  • Linux Clusters

In contrast, some Tightly Coupled examples:

  • Semetrical-Multi-Processing (SMP) Operating systems - e.g. Fedora 9
  • Multi-threaded CPUs
  • Multi-Core CPUs

In today's computing, examples of both operating in a single overall system is not uncommon. For example, take modern Pentium dual or quad core CPUs running Fedora 9 - these are tightly-coupled computing systems. Then, combine several of them in a loosely coupled Linux Cluster and you now have both loosely and tightly coupled computing going on! Oh, isn't modern hardware wonderful!

SSIS Excel Import Forcing Incorrect Column Type

I've seen this issue before, it's Excel that is the issue not SSIS. Excel samples the 1st few rows and then infers the data type even if you explicitly set it to text. What you need to do is put this into the Excel file connection string in the SSIS package. This instruction tells Excel that the columns contain mixed data types and hints it to do extra checking before deciding that the column is a numeric type when in fact it's not.

;Extended Properties="IMEX=1"

It should work with this (in most cases). The safer thing to do is export the Excel data to tab delimited text and use SSIS to import that.

The response content cannot be parsed because the Internet Explorer engine is not available, or

In your invoke web request just use the parameter -UseBasicParsing

e.g. in your script (line 2) you should use:

$rss = Invoke-WebRequest -Uri $url -UseBasicParsing

According to the documentation, this parameter is necessary on systems where IE isn't installed or configured:

Uses the response object for HTML content without Document Object Model (DOM) parsing. This parameter is required when Internet Explorer is not installed on the computers, such as on a Server Core installation of a Windows Server operating system.

How to check if mysql database exists

I am using simply the following query:

"USE 'DBname'"

Then check if the result is FALSE. Otherwise, there might be an access denied error, but I cannot know that. So, in case of privileges involved, one can use:

"SHOW DATABASES LIKE 'DBname'"

as already mentioned earlier.

Code for Greatest Common Divisor in Python

I had to do something like this for a homework assignment using while loops. Not the most efficient way, but if you don't want to use a function this works:

num1 = 20
num1_list = []
num2 = 40
num2_list = []
x = 1
y = 1
while x <= num1:
    if num1 % x == 0:
        num1_list.append(x)
    x += 1
while y <= num2:
    if num2 % y == 0:
        num2_list.append(y)
    y += 1
xy = list(set(num1_list).intersection(num2_list))
print(xy[-1])

How to read a configuration file in Java

It depends.

Start with Basic I/O, take a look at Properties, take a look at Preferences API and maybe even Java API for XML Processing and Java Architecture for XML Binding

And if none of those meet your particular needs, you could even look at using some kind of Database

Setting the filter to an OpenFileDialog to allow the typical image formats?

To filter images files, use this code sample.

//Create a new instance of openFileDialog
OpenFileDialog res = new OpenFileDialog();

//Filter
res.Filter = "Image Files|*.jpg;*.jpeg;*.png;*.gif;*.tif;...";

//When the user select the file
if (res.ShowDialog() == DialogResult.OK)
{
   //Get the file's path
   var filePath = res.FileName;
   //Do something
   ....
}

Get first letter of a string from column

.str.get

This is the simplest to specify string methods

# Setup
df = pd.DataFrame({'A': ['xyz', 'abc', 'foobar'], 'B': [123, 456, 789]})
df

        A    B
0     xyz  123
1     abc  456
2  foobar  789

df.dtypes

A    object
B     int64
dtype: object

For string (read:object) type columns, use

df['C'] = df['A'].str[0]
# Similar to,
df['C'] = df['A'].str.get(0)

.str handles NaNs by returning NaN as the output.

For non-numeric columns, an .astype conversion is required beforehand, as shown in @Ed Chum's answer.

# Note that this won't work well if the data has NaNs. 
# It'll return lowercase "n"
df['D'] = df['B'].astype(str).str[0]

df
        A    B  C  D
0     xyz  123  x  1
1     abc  456  a  4
2  foobar  789  f  7

List Comprehension and Indexing

There is enough evidence to suggest a simple list comprehension will work well here and probably be faster.

# For string columns
df['C'] = [x[0] for x in df['A']]

# For numeric columns
df['D'] = [str(x)[0] for x in df['B']]

df
        A    B  C  D
0     xyz  123  x  1
1     abc  456  a  4
2  foobar  789  f  7

If your data has NaNs, then you will need to handle this appropriately with an if/else in the list comprehension,

df2 = pd.DataFrame({'A': ['xyz', np.nan, 'foobar'], 'B': [123, 456, np.nan]})
df2

        A      B
0     xyz  123.0
1     NaN  456.0
2  foobar    NaN

# For string columns
df2['C'] = [x[0] if isinstance(x, str) else np.nan for x in df2['A']]

# For numeric columns
df2['D'] = [str(x)[0] if pd.notna(x) else np.nan for x in df2['B']]

        A      B    C    D
0     xyz  123.0    x    1
1     NaN  456.0  NaN    4
2  foobar    NaN    f  NaN

Let's do some timeit tests on some larger data.

df_ = df.copy()
df = pd.concat([df_] * 5000, ignore_index=True) 

%timeit df.assign(C=df['A'].str[0])
%timeit df.assign(D=df['B'].astype(str).str[0])

%timeit df.assign(C=[x[0] for x in df['A']])
%timeit df.assign(D=[str(x)[0] for x in df['B']])

12 ms ± 253 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
27.1 ms ± 1.38 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)

3.77 ms ± 110 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
7.84 ms ± 145 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

List comprehensions are 4x faster.

How can I turn a string into a list in Python?

The list() function [docs] will convert a string into a list of single-character strings.

>>> list('hello')
['h', 'e', 'l', 'l', 'o']

Even without converting them to lists, strings already behave like lists in several ways. For example, you can access individual characters (as single-character strings) using brackets:

>>> s = "hello"
>>> s[1]
'e'
>>> s[4]
'o'

You can also loop over the characters in the string as you can loop over the elements of a list:

>>> for c in 'hello':
...     print c + c,
... 
hh ee ll ll oo

Convert a python 'type' object to a string

Using str()

 typeOfOneAsString=str(type(1))

How to get label text value form a html page?

Use innerText/textContent:

  var el = document.getElementById('*spaM4');
  console.log(el.innerText || el.textContent);

Fiddle: http://jsfiddle.net/NeTgC/2/

How to clear or stop timeInterval in angularjs?

When you want to create interval store promise to variable:

var p = $interval(function() { ... },1000);

And when you want to stop / clear the interval simply use:

$interval.cancel(p);

Virtual network interface in Mac OS X

ifconfig interfacename create will create a virtual interface,

Function Pointers in Java

Check the closures how they have been implemented in the lambdaj library. They actually have a behavior very similar to C# delegates:

http://code.google.com/p/lambdaj/wiki/Closures

SQLiteDatabase.query method

tableColumns

  • null for all columns as in SELECT * FROM ...
  • new String[] { "column1", "column2", ... } for specific columns as in SELECT column1, column2 FROM ... - you can also put complex expressions here:
    new String[] { "(SELECT max(column1) FROM table1) AS max" } would give you a column named max holding the max value of column1

whereClause

  • the part you put after WHERE without that keyword, e.g. "column1 > 5"
  • should include ? for things that are dynamic, e.g. "column1=?" -> see whereArgs

whereArgs

  • specify the content that fills each ? in whereClause in the order they appear

the others

  • just like whereClause the statement after the keyword or null if you don't use it.

Example

String[] tableColumns = new String[] {
    "column1",
    "(SELECT max(column1) FROM table2) AS max"
};
String whereClause = "column1 = ? OR column1 = ?";
String[] whereArgs = new String[] {
    "value1",
    "value2"
};
String orderBy = "column1";
Cursor c = sqLiteDatabase.query("table1", tableColumns, whereClause, whereArgs,
        null, null, orderBy);

// since we have a named column we can do
int idx = c.getColumnIndex("max");

is equivalent to the following raw query

String queryString =
    "SELECT column1, (SELECT max(column1) FROM table1) AS max FROM table1 " +
    "WHERE column1 = ? OR column1 = ? ORDER BY column1";
sqLiteDatabase.rawQuery(queryString, whereArgs);

By using the Where/Bind -Args version you get automatically escaped values and you don't have to worry if input-data contains '.

Unsafe: String whereClause = "column1='" + value + "'";
Safe: String whereClause = "column1=?";

because if value contains a ' your statement either breaks and you get exceptions or does unintended things, for example value = "XYZ'; DROP TABLE table1;--" might even drop your table since the statement would become two statements and a comment:

SELECT * FROM table1 where column1='XYZ'; DROP TABLE table1;--'

using the args version XYZ'; DROP TABLE table1;-- would be escaped to 'XYZ''; DROP TABLE table1;--' and would only be treated as a value. Even if the ' is not intended to do bad things it is still quite common that people have it in their names or use it in texts, filenames, passwords etc. So always use the args version. (It is okay to build int and other primitives directly into whereClause though)

how can I set visible back to true in jquery

The problem is that since you are using ASP.NET controls with a runat attribute, the ID of the control is not actually "test1". It's "test1" with a long string attached to it.

socket programming multiple client to one server

This is the echo server handling multiple clients... Runs fine and good using Threads

// echo server
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;


public class Server_X_Client {
public static void main(String args[]){


    Socket s=null;
    ServerSocket ss2=null;
    System.out.println("Server Listening......");
    try{
        ss2 = new ServerSocket(4445); // can also use static final PORT_NUM , when defined

    }
    catch(IOException e){
    e.printStackTrace();
    System.out.println("Server error");

    }

    while(true){
        try{
            s= ss2.accept();
            System.out.println("connection Established");
            ServerThread st=new ServerThread(s);
            st.start();

        }

    catch(Exception e){
        e.printStackTrace();
        System.out.println("Connection Error");

    }
    }

}

}

class ServerThread extends Thread{  

    String line=null;
    BufferedReader  is = null;
    PrintWriter os=null;
    Socket s=null;

    public ServerThread(Socket s){
        this.s=s;
    }

    public void run() {
    try{
        is= new BufferedReader(new InputStreamReader(s.getInputStream()));
        os=new PrintWriter(s.getOutputStream());

    }catch(IOException e){
        System.out.println("IO error in server thread");
    }

    try {
        line=is.readLine();
        while(line.compareTo("QUIT")!=0){

            os.println(line);
            os.flush();
            System.out.println("Response to Client  :  "+line);
            line=is.readLine();
        }   
    } catch (IOException e) {

        line=this.getName(); //reused String line for getting thread name
        System.out.println("IO Error/ Client "+line+" terminated abruptly");
    }
    catch(NullPointerException e){
        line=this.getName(); //reused String line for getting thread name
        System.out.println("Client "+line+" Closed");
    }

    finally{    
    try{
        System.out.println("Connection Closing..");
        if (is!=null){
            is.close(); 
            System.out.println(" Socket Input Stream Closed");
        }

        if(os!=null){
            os.close();
            System.out.println("Socket Out Closed");
        }
        if (s!=null){
        s.close();
        System.out.println("Socket Closed");
        }

        }
    catch(IOException ie){
        System.out.println("Socket Close Error");
    }
    }//end finally
    }
}

Also here is the code for the client.. Just execute this code for as many times as you want to create multiple client..

// A simple Client Server Protocol .. Client for Echo Server

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;

public class NetworkClient {

public static void main(String args[]) throws IOException{


    InetAddress address=InetAddress.getLocalHost();
    Socket s1=null;
    String line=null;
    BufferedReader br=null;
    BufferedReader is=null;
    PrintWriter os=null;

    try {
        s1=new Socket(address, 4445); // You can use static final constant PORT_NUM
        br= new BufferedReader(new InputStreamReader(System.in));
        is=new BufferedReader(new InputStreamReader(s1.getInputStream()));
        os= new PrintWriter(s1.getOutputStream());
    }
    catch (IOException e){
        e.printStackTrace();
        System.err.print("IO Exception");
    }

    System.out.println("Client Address : "+address);
    System.out.println("Enter Data to echo Server ( Enter QUIT to end):");

    String response=null;
    try{
        line=br.readLine(); 
        while(line.compareTo("QUIT")!=0){
                os.println(line);
                os.flush();
                response=is.readLine();
                System.out.println("Server Response : "+response);
                line=br.readLine();

            }



    }
    catch(IOException e){
        e.printStackTrace();
    System.out.println("Socket read Error");
    }
    finally{

        is.close();os.close();br.close();s1.close();
                System.out.println("Connection Closed");

    }

}
}

Finding the handle to a WPF window

If you want window handles for ALL of your application's Windows for some reason, you can use the Application.Windows property to get at all the Windows and then use WindowInteropHandler to get at their handles as you have already demonstrated.

python catch exception and continue try block

No, you cannot do that. That's just the way Python has its syntax. Once you exit a try-block because of an exception, there is no way back in.

What about a for-loop though?

funcs = do_smth1, do_smth2

for func in funcs:
    try:
        func()
    except Exception:
        pass  # or you could use 'continue'

Note however that it is considered a bad practice to have a bare except. You should catch for a specific exception instead. I captured for Exception because that's as good as I can do without knowing what exceptions the methods might throw.

How to enable directory listing in apache web server

I solved the problem by enabling the mod_autoindex from Apache. It was disabled by default.

sudo a2enmod autoindex

How would I access variables from one class to another?

var1 and var2 is an Instance variables of ClassA. Create an Instance of ClassB and when calling the methodA it will check the methodA in Child class (ClassB) first, If methodA is not present in ClassB you need to invoke the ClassA by using the super() method which will get you all the methods implemented in ClassA. Now, you can access all the methods and attributes of ClassB.

class ClassA(object):
    def __init__(self):
        self.var1 = 1
        self.var2 = 2

    def methodA(self):
        self.var1 = self.var1 + self.var2
        return self.var1


class ClassB(ClassA):
    def __init__(self):
        super().__init__()
        print("var1",self.var1)
        print("var2",self.var2)


object1 = ClassB()
sum = object1.methodA()
print(sum)

The name 'ConfigurationManager' does not exist in the current context

In your project, right-click, Add Reference..., in the .NET tab, find the System.Configuration component name and click OK.

using System.Configuration tells the compiler/IntelliSense to search in that namespace for any classes you use. Otherwise, you would have to use the full name (System.Configuration.ConfigurationManager) every time. But if you don't add the reference, that namespace/class will not be found anywhere.

Note that a DLL can have any namespace, so the file System.Configuration.dll could, in theory, have the namespace Some.Random.Name. For clarity/consistency they're usually the same, but there are exceptions.

python: sys is not defined

Move import sys outside of the try-except block:

import sys
try:
    # ...
except ImportError:
    # ...

If any of the imports before the import sys line fails, the rest of the block is not executed, and sys is never imported. Instead, execution jumps to the exception handling block, where you then try to access a non-existing name.

sys is a built-in module anyway, it is always present as it holds the data structures to track imports; if importing sys fails, you have bigger problems on your hand (as that would indicate that all module importing is broken).

Can I use GDB to debug a running process?

You can attach to a running process with gdb -p PID.

__FILE__, __LINE__, and __FUNCTION__ usage in C++

FYI: g++ offers the non-standard __PRETTY_FUNCTION__ macro. Until just now I did not know about C99 __func__ (thanks Evan!). I think I still prefer __PRETTY_FUNCTION__ when it's available for the extra class scoping.

PS:

static string  getScopedClassMethod( string thePrettyFunction )
{
  size_t index = thePrettyFunction . find( "(" );
  if ( index == string::npos )
    return thePrettyFunction;  /* Degenerate case */

  thePrettyFunction . erase( index );

  index = thePrettyFunction . rfind( " " );
  if ( index == string::npos )
    return thePrettyFunction;  /* Degenerate case */

  thePrettyFunction . erase( 0, index + 1 );

  return thePrettyFunction;   /* The scoped class name. */
}

How to create windows service from java jar?

Use nssm.exe but remember to set the AppDirectory or any required libraries or resources will not be accessible. By default nssm set the current working directory to the that of the application, java.exe, not the jar. So do this to create a batch script:

    pushd <path-to-jar>
    nssm.exe install "<service-name>" "<path-to-java.exe>" "-jar <name-of-jar>"
    nssm.exe set "<service-name>" AppDirectory "<path-to-jar>"

This should fix the service paused issue.

Hide Command Window of .BAT file that Executes Another .EXE File

Create a .vbs file with this code:

CreateObject("Wscript.Shell").Run "your_batch.bat",0,True

This .vbs will run your_batch.bat hidden.

Works fine for me.

How to add a single item to a Pandas Series

Here is another thought n for appending multiple items in one line without changing the name of series. However, this may be not as efficient as the other answer.

>>> df = pd.Series(np.random.random(5), name='random')
>>> df

0    0.363885
1    0.402623
2    0.450449
3    0.172917
4    0.983481
Name: random, dtype: float64


>>> df.to_frame().T.assign(a=3, b=2, c=5).squeeze()

0    0.363885
1    0.402623
2    0.450449
3    0.172917
4    0.983481
a    3.000000
b    2.000000
c    5.000000
Name: random, dtype: float64

SQL Server ORDER BY date and nulls last

smalldatetime has range up to June 6, 2079 so you can use

ORDER BY ISNULL(Next_Contact_Date, '2079-06-05T23:59:00')

If no legitimate records will have that date.

If this is not an assumption you fancy relying on a more robust option is sorting on two columns.

ORDER BY CASE WHEN Next_Contact_Date IS NULL THEN 1 ELSE 0 END, Next_Contact_Date

Both of the above suggestions are not able to use an index to avoid a sort however and give similar looking plans.

enter image description here

One other possibility if such an index exists is

SELECT 1 AS Grp, Next_Contact_Date 
FROM T 
WHERE Next_Contact_Date IS NOT NULL
UNION ALL
SELECT 2 AS Grp, Next_Contact_Date 
FROM T 
WHERE Next_Contact_Date IS NULL
ORDER BY Grp, Next_Contact_Date

Plan

What is the size of a boolean variable in Java?

I read that Java reserves one byte for a boolean datatype, but it uses only one bit. However, the documentation says that "its "size" isn't something that's precisely defined". See here.

python "TypeError: 'numpy.float64' object cannot be interpreted as an integer"

N=np.floor(np.divide(l,delta))
...
for j in range(N[i]/2):

N[i]/2 will be a float64 but range() expects an integer. Just cast the call to

for j in range(int(N[i]/2)):

PHP list of specific files in a directory

$it = new RegexIterator(new DirectoryIterator("."), "/\\.xml\$/i"));

foreach ($it as $filename) {
    //...
}

You can also use the recursive variants of the iterators to traverse an entire directory hierarchy.

How to replace all special character into a string using C#

Assume you want to replace symbols which are not digits or letters (and _ character as @Guffa correctly pointed):

string input = "Hello@Hello&Hello(Hello)";
string result = Regex.Replace(input, @"[^\w\d]", ",");
// Hello,Hello,Hello,Hello,

You can add another symbols which should not be replaced. E.g. if you want white space symbols to stay, then just add \s to pattern: \[^\w\d\s]

How to set password for Redis?

sudo nano /etc/redis/redis.conf 

find and uncomment line # requirepass foobared, then restart server

now you password is foobared

How do I specify row heights in CSS Grid layout?

One of the Related posts gave me the (simple) answer.

Apparently the auto value on the grid-template-rows property does exactly what I was looking for.

.grid {
    display:grid;
    grid-template-columns: 1fr 1.5fr 1fr;
    grid-template-rows: auto auto 1fr 1fr 1fr auto auto;
    grid-gap:10px;
    height: calc(100vh - 10px);
}

How to detect chrome and safari browser (webkit)

/WebKit/.test(navigator.userAgent) — that's it.

How to change the port of Tomcat from 8080 to 80?

I tried changing the port from 8080 to 80 in the server.xml but it didn't work for me. Then I found alternative, update the iptables which i'm sure there is an impact on performance.

I use the following commands:

sudo /sbin/iptables -t nat -I PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
sudo /sbin/service iptables save

http://www.excelsior-usa.com/articles/tomcat-amazon-ec2-advanced.html#port80

How to list the properties of a JavaScript object?

The solution work on my cases and cross-browser:

var getKeys = function(obj) {
    var type = typeof  obj;
    var isObjectType = type === 'function' || type === 'object' || !!obj;

    // 1
    if(isObjectType) {
        return Object.keys(obj);
    }

    // 2
    var keys = [];
    for(var i in obj) {
        if(obj.hasOwnProperty(i)) {
            keys.push(i)
        }
    }
    if(keys.length) {
        return keys;
    }

    // 3 - bug for ie9 <
    var hasEnumbug = !{toString: null}.propertyIsEnumerable('toString');
    if(hasEnumbug) {
        var nonEnumerableProps = ['valueOf', 'isPrototypeOf', 'toString',
            'propertyIsEnumerable', 'hasOwnProperty', 'toLocaleString'];

        var nonEnumIdx = nonEnumerableProps.length;

        while (nonEnumIdx--) {
            var prop = nonEnumerableProps[nonEnumIdx];
            if (Object.prototype.hasOwnProperty.call(obj, prop)) {
                keys.push(prop);
            }
        }

    }

    return keys;
};

How to use ArrayAdapter<myClass>

Implement custom adapter for your class:

public class MyClassAdapter extends ArrayAdapter<MyClass> {

    private static class ViewHolder {
        private TextView itemView;
    }

    public MyClassAdapter(Context context, int textViewResourceId, ArrayList<MyClass> items) {
        super(context, textViewResourceId, items);
    }

    public View getView(int position, View convertView, ViewGroup parent) {

        if (convertView == null) {
            convertView = LayoutInflater.from(this.getContext())
            .inflate(R.layout.listview_association, parent, false);

            viewHolder = new ViewHolder();
            viewHolder.itemView = (TextView) convertView.findViewById(R.id.ItemView);

            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        MyClass item = getItem(position);
        if (item!= null) {
            // My layout has only one TextView
                // do whatever you want with your string and long
            viewHolder.itemView.setText(String.format("%s %d", item.reason, item.long_val));
        }

        return convertView;
    }
}

For those not very familiar with the Android framework, this is explained in better detail here: https://github.com/codepath/android_guides/wiki/Using-an-ArrayAdapter-with-ListView.

A circular reference was detected while serializing an object of type 'SubSonic.Schema .DatabaseColumn'.

Its because of the new DbContext T4 template that is used for generating the EntityFramework entities. In order to be able to perform the change tracking, this templates uses the Proxy pattern, by wrapping your nice POCOs with them. This then causes the issues when serializing with the JavaScriptSerializer.

So then the 2 solutions are:

  1. Either you just serialize and return the properties you need on the client
  2. You may switch off the automatic generation of proxies by setting it on the context's configuration

    context.Configuration.ProxyCreationEnabled = false;

Very well explained in the below article.

http://juristr.com/blog/2011/08/javascriptserializer-circular-reference/

SCRIPT438: Object doesn't support property or method IE

I had the following

document.getElementById("search-button") != null

which worked fine in all browsers except ie8. ( I didnt check ie6 or ie7)

I changed it to

document.getElementById("searchBtn") != null

and updated the id attribute on the field in my html and it now works in ie8

Convert floating point number to a certain precision, and then copy to string

Using round:

>>> numvar = 135.12345678910
>>> str(round(numvar, 9))
'135.123456789'

Angular - ui-router get previous state

Ok, I know that I am late to the party here, but I am new to angular. I am trying to make this fit into the John Papa style guide here. I wanted to make this reusable so I created in a block. Here is what I came up with:

previousStateProvider

(function () {
'use strict';

angular.module('blocks.previousState')
       .provider('previousState', previousStateProvider);

previousStateProvider.$inject = ['$rootScopeProvider'];

function previousStateProvider($rootScopeProvider) {
    this.$get = PreviousState;

    PreviousState.$inject = ['$rootScope'];

    /* @ngInject */
    function PreviousState($rootScope) {
        $rootScope.previousParms;
        $rootScope.previousState;
        $rootScope.currentState;

        $rootScope.$on('$stateChangeSuccess', function (ev, to, toParams, from, fromParams) {
            $rootScope.previousParms = fromParams;
            $rootScope.previousState = from.name;
            $rootScope.currentState = to.name;
        });
    }
}
})();

core.module

(function () {
'use strict';

angular.module('myApp.Core', [
    // Angular modules 
    'ngMessages',
    'ngResource',

    // Custom modules 
    'blocks.previousState',
    'blocks.router'

    // 3rd Party Modules
]);
})();

core.config

(function () {
'use strict';

var core = angular.module('myApp.Core');

core.run(appRun);

function appRun(previousState) {
    // do nothing. just instantiating the state handler
}
})();

Any critique on this code will only help me, so please let me know where I can improve this code.

Add params to given URL in Python

Use the various urlparse functions to tear apart the existing URL, urllib.urlencode() on the combined dictionary, then urlparse.urlunparse() to put it all back together again.

Or just take the result of urllib.urlencode() and concatenate it to the URL appropriately.

Playing HTML5 video on fullscreen in android webview

Thank you so much for that class, Cristian.

I made a minor tweak to it so that the custom loading view is optional, like so:

  @Override
    public View getVideoLoadingProgressView() // Video will start loading, only called in the case of VideoView (typically API level 10-)
    {
        if (loadingView == null)
        {
            return super.getVideoLoadingProgressView();
        }
        else
        {
            loadingView.setVisibility(View.VISIBLE);
            return loadingView;
        }
    }

I also added a new constructor that just takes two parameters. Anyway, just a minor simplification if you don't need the loading view. Thanks again for providing this.

Calculate RSA key fingerprint

If your SSH agent is running, it is

ssh-add -l

to list RSA fingerprints of all identities, or -L for listing public keys.

If your agent is not running, try:

ssh-agent sh -c 'ssh-add; ssh-add -l'

And for your public keys:

ssh-agent sh -c 'ssh-add; ssh-add -L'

If you get the message: 'The agent has no identities.', then you have to generate your RSA key by ssh-keygen first.

Using the Web.Config to set up my SQL database connection string?

http://www.connectionstrings.com is a site where you can find a lot of connection strings. All that you need to do is copy-paste and modify it to suit your needs. It is sure to have all the connection strings for all of your needs.

Check if a class is derived from a generic class

(Reposted due to a massive rewrite)

JaredPar's code answer is fantastic, but I have a tip that would make it unnecessary if your generic types are not based on value type parameters. I was hung up on why the "is" operator would not work, so I have also documented the results of my experimentation for future reference. Please enhance this answer to further enhance its clarity.

TIP:

If you make certain that your GenericClass implementation inherits from an abstract non-generic base class such as GenericClassBase, you could ask the same question without any trouble at all like this:

typeof(Test).IsSubclassOf(typeof(GenericClassBase))

IsSubclassOf()

My testing indicates that IsSubclassOf() does not work on parameterless generic types such as

typeof(GenericClass<>)

whereas it will work with

typeof(GenericClass<SomeType>)

Therefore the following code will work for any derivation of GenericClass<>, assuming you are willing to test based on SomeType:

typeof(Test).IsSubclassOf(typeof(GenericClass<SomeType>))

The only time I can imagine that you would want to test by GenericClass<> is in a plug-in framework scenario.


Thoughts on the "is" operator

At design-time C# does not allow the use of parameterless generics because they are essentially not a complete CLR type at that point. Therefore, you must declare generic variables with parameters, and that is why the "is" operator is so powerful for working with objects. Incidentally, the "is" operator also can not evaluate parameterless generic types.

The "is" operator will test the entire inheritance chain, including interfaces.

So, given an instance of any object, the following method will do the trick:

bool IsTypeof<T>(object t)
{
    return (t is T);
}

This is sort of redundant, but I figured I would go ahead and visualize it for everybody.

Given

var t = new Test();

The following lines of code would return true:

bool test1 = IsTypeof<GenericInterface<SomeType>>(t);

bool test2 = IsTypeof<GenericClass<SomeType>>(t);

bool test3 = IsTypeof<Test>(t);

On the other hand, if you want something specific to GenericClass, you could make it more specific, I suppose, like this:

bool IsTypeofGenericClass<SomeType>(object t)
{
    return (t is GenericClass<SomeType>);
}

Then you would test like this:

bool test1 = IsTypeofGenericClass<SomeType>(t);

Search code inside a Github project

Go here: https://github.com/search and enter "pattern repo:user_name/repo_name".

For example, to search for cnn_learner in the fastai repo of user fastai, enter this:

cnn_learner repo:fastai/fastai

That's it. The only annoyance is you'll need an extra click. It will tell you:

We couldn’t find any repositories matching 'cnn_learner repo:fastai/fastai'

because by default it searches for repositories matching that search string...

So just click on the left on "Code" and it will display what you want.

Or get the code search results directly with a URL like this:

https://github.com/search?q=cnn_learner+repo%3Afastai%2Ffastai&type=code

JavaScript object: access variable property by name as string

You don't need a function for it - simply use the bracket notation:

var side = columns['right'];

This is equal to dot notation, var side = columns.right;, except the fact that right could also come from a variable, function return value, etc., when using bracket notation.

If you NEED a function for it, here it is:

function read_prop(obj, prop) {
    return obj[prop];
}

To answer some of the comments below that aren't directly related to the original question, nested objects can be referenced through multiple brackets. If you have a nested object like so:

var foo = { a: 1, b: 2, c: {x: 999, y:998, z: 997}};

you can access property x of c as follows:

var cx = foo['c']['x']

If a property is undefined, an attempt to reference it will return undefined (not null or false):

foo['c']['q'] === null
// returns false

foo['c']['q'] === false
// returns false

foo['c']['q'] === undefined
// returns true

Creating a Jenkins environment variable using Groovy

On my side it only worked this way by replacing an existing parameter.

def artifactNameParam = new StringParameterValue('CopyProjectArtifactName', 'bla bla bla')
build.replaceAction(new ParametersAction(artifactNameParam))

Additionally this script must be run with system groovy.

A groovy must be manually installed on that system and the bin dir of groovy must be added to path. Additionally in the lib folder I had to add jenkins-core.jar.

Then it was possible to modify a parameter in a groovy script and get the modified value in a batch script after to continue work.

The server encountered an internal error that prevented it from fulfilling this request - in servlet 3.0

In here:

    if (ValidationUtils.isNullOrEmpty(lastName)) {
        registrationErrors.add(ValidationErrors.LAST_NAME);
    }
    if (!ValidationUtils.isEmailValid(email)) {
        registrationErrors.add(ValidationErrors.EMAIL);
    }

you check for null or empty value on lastname, but in isEmailValid you don't check for empty value. Something like this should do

    if (ValidationUtils.isNullOrEmpty(email) || !ValidationUtils.isEmailValid(email)) {
        registrationErrors.add(ValidationErrors.EMAIL);
    }

or better yet, fix your ValidationUtils.isEmailValid() to cope with null email values. It shouldn't crash, it should just return false.

How to count items in JSON data

import json

json_data = json.dumps({
  "result":[
    {
      "run":[
        {
          "action":"stop"
        },
        {
          "action":"start"
        },
        {
          "action":"start"
        }
      ],
      "find": "true"
    }
  ]
})

item_dict = json.loads(json_data)
print len(item_dict['result'][0]['run'])

Convert it in dict.

When should we use mutex and when should we use semaphore

See "The Toilet Example" - http://pheatt.emporia.edu/courses/2010/cs557f10/hand07/Mutex%20vs_%20Semaphore.htm:

Mutex:

Is a key to a toilet. One person can have the key - occupy the toilet - at the time. When finished, the person gives (frees) the key to the next person in the queue.

Officially: "Mutexes are typically used to serialise access to a section of re-entrant code that cannot be executed concurrently by more than one thread. A mutex object only allows one thread into a controlled section, forcing other threads which attempt to gain access to that section to wait until the first thread has exited from that section." Ref: Symbian Developer Library

(A mutex is really a semaphore with value 1.)

Semaphore:

Is the number of free identical toilet keys. Example, say we have four toilets with identical locks and keys. The semaphore count - the count of keys - is set to 4 at beginning (all four toilets are free), then the count value is decremented as people are coming in. If all toilets are full, ie. there are no free keys left, the semaphore count is 0. Now, when eq. one person leaves the toilet, semaphore is increased to 1 (one free key), and given to the next person in the queue.

Officially: "A semaphore restricts the number of simultaneous users of a shared resource up to a maximum number. Threads can request access to the resource (decrementing the semaphore), and can signal that they have finished using the resource (incrementing the semaphore)." Ref: Symbian Developer Library

How to define and use function inside Jenkins Pipeline config?

First off, you shouldn't add $ when you're outside of strings ($class in your first function being an exception), so it should be:

def doCopyMibArtefactsHere(projectName) {
    step ([
        $class: 'CopyArtifact',
        projectName: projectName,
        filter: '**/**.mib',
        fingerprintArtifacts: true, 
        flatten: true
    ]);
}

def BuildAndCopyMibsHere(projectName, params) {
    build job: project, parameters: params
    doCopyMibArtefactsHere(projectName)
}
...

Now, as for your problem; the second function takes two arguments while you're only supplying one argument at the call. Either you have to supply two arguments at the call:

...
node { 
    stage('Prepare Mib'){
        BuildAndCopyMibsHere('project1', null)
    }
}

... or you need to add a default value to the functions' second argument:

def BuildAndCopyMibsHere(projectName, params = null) {
    build job: project, parameters: params
    doCopyMibArtefactsHere($projectName)
}

Bundler::GemNotFound: Could not find rake-10.3.2 in any of the sources

Remove your Gemfile.lock.

Move to bash if you are using zsh.

sudo bash
gem update --system 

Now run command bundle to create a new Gemfile.lock file. Move back to your zsh sudo exec zsh now run your rake commands.

Does Python have a string 'contains' substring method?

if needle in haystack: is the normal use, as @Michael says -- it relies on the in operator, more readable and faster than a method call.

If you truly need a method instead of an operator (e.g. to do some weird key= for a very peculiar sort...?), that would be 'haystack'.__contains__. But since your example is for use in an if, I guess you don't really mean what you say;-). It's not good form (nor readable, nor efficient) to use special methods directly -- they're meant to be used, instead, through the operators and builtins that delegate to them.

How can I display a tooltip on an HTML "option" tag?

At least on firefox, you can set a "title" attribute on the option tag:

<option value="" title="Tooltip">Some option</option>

Action Bar's onClick listener for the Home button

if we use the system given action bar following code works fine

getActionBar().setHomeButtonEnabled(true);

@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {

    int itemId = item.getItemId();
    switch (itemId) {
    case android.R.id.home:
      //do your action here.
        break;

    }

    return true;
}

xml.LoadData - Data at the root level is invalid. Line 1, position 1

If your xml is in a string use the following to remove any byte order mark:

        xml = new Regex("\\<\\?xml.*\\?>").Replace(xml, "");

How to implement a ConfigurationSection with a ConfigurationElementCollection

If you are looking for a custom configuration section like following

<CustomApplicationConfig>
        <Credentials Username="itsme" Password="mypassword"/>
        <PrimaryAgent Address="10.5.64.26" Port="3560"/>
        <SecondaryAgent Address="10.5.64.7" Port="3570"/>
        <Site Id="123" />
        <Lanes>
          <Lane Id="1" PointId="north" Direction="Entry"/>
          <Lane Id="2" PointId="south" Direction="Exit"/>
        </Lanes> 
</CustomApplicationConfig>

then you can use my implementation of configuration section so to get started add System.Configuration assembly reference to your project

Look at the each nested elements I used, First one is Credentials with two attributes so lets add it first

Credentials Element

public class CredentialsConfigElement : System.Configuration.ConfigurationElement
    {
        [ConfigurationProperty("Username")]
        public string Username
        {
            get 
            {
                return base["Username"] as string;
            }
        }

        [ConfigurationProperty("Password")]
        public string Password
        {
            get
            {
                return base["Password"] as string;
            }
        }
    }

PrimaryAgent and SecondaryAgent

Both has the same attributes and seem like a Address to a set of servers for a primary and a failover, so you just need to create one element class for both of those like following

public class ServerInfoConfigElement : ConfigurationElement
    {
        [ConfigurationProperty("Address")]
        public string Address
        {
            get
            {
                return base["Address"] as string;
            }
        }

        [ConfigurationProperty("Port")]
        public int? Port
        {
            get
            {
                return base["Port"] as int?;
            }
        }
    }

I'll explain how to use two different element with one class later in this post, let us skip the SiteId as there is no difference in it. You just have to create one class same as above with one property only. let us see how to implement Lanes collection

it is splitted in two parts first you have to create an element implementation class then you have to create collection element class

LaneConfigElement

public class LaneConfigElement : ConfigurationElement
    {
        [ConfigurationProperty("Id")]
        public string Id
        {
            get
            {
                return base["Id"] as string;
            }
        }

        [ConfigurationProperty("PointId")]
        public string PointId
        {
            get
            {
                return base["PointId"] as string;
            }
        }

        [ConfigurationProperty("Direction")]
        public Direction? Direction
        {
            get
            {
                return base["Direction"] as Direction?;
            }
        }
    }

    public enum Direction
    { 
        Entry,
        Exit
    }

you can notice that one attribute of LanElement is an Enumeration and if you try to use any other value in configuration which is not defined in Enumeration application will throw an System.Configuration.ConfigurationErrorsException on startup. Ok lets move on to Collection Definition

[ConfigurationCollection(typeof(LaneConfigElement), AddItemName = "Lane", CollectionType = ConfigurationElementCollectionType.BasicMap)]
    public class LaneConfigCollection : ConfigurationElementCollection
    {
        public LaneConfigElement this[int index]
        {
            get { return (LaneConfigElement)BaseGet(index); }
            set
            {
                if (BaseGet(index) != null)
                {
                    BaseRemoveAt(index);
                }
                BaseAdd(index, value);
            }
        }

        public void Add(LaneConfigElement serviceConfig)
        {
            BaseAdd(serviceConfig);
        }

        public void Clear()
        {
            BaseClear();
        }

        protected override ConfigurationElement CreateNewElement()
        {
            return new LaneConfigElement();
        }

        protected override object GetElementKey(ConfigurationElement element)
        {
            return ((LaneConfigElement)element).Id;
        }

        public void Remove(LaneConfigElement serviceConfig)
        {
            BaseRemove(serviceConfig.Id);
        }

        public void RemoveAt(int index)
        {
            BaseRemoveAt(index);
        }

        public void Remove(String name)
        {
            BaseRemove(name);
        }

    }

you can notice that I have set the AddItemName = "Lane" you can choose whatever you like for your collection entry item, i prefer to use "add" the default one but i changed it just for the sake of this post.

Now all of our nested Elements have been implemented now we should aggregate all of those in a class which has to implement System.Configuration.ConfigurationSection

CustomApplicationConfigSection

public class CustomApplicationConfigSection : System.Configuration.ConfigurationSection
    {
        private static readonly ILog log = LogManager.GetLogger(typeof(CustomApplicationConfigSection));
        public const string SECTION_NAME = "CustomApplicationConfig";

        [ConfigurationProperty("Credentials")]
        public CredentialsConfigElement Credentials
        {
            get
            {
                return base["Credentials"] as CredentialsConfigElement;
            }
        }

        [ConfigurationProperty("PrimaryAgent")]
        public ServerInfoConfigElement PrimaryAgent
        {
            get
            {
                return base["PrimaryAgent"] as ServerInfoConfigElement;
            }
        }

        [ConfigurationProperty("SecondaryAgent")]
        public ServerInfoConfigElement SecondaryAgent
        {
            get
            {
                return base["SecondaryAgent"] as ServerInfoConfigElement;
            }
        }

        [ConfigurationProperty("Site")]
        public SiteConfigElement Site
        {
            get
            {
                return base["Site"] as SiteConfigElement;
            }
        }

        [ConfigurationProperty("Lanes")]
        public LaneConfigCollection Lanes
        {
            get { return base["Lanes"] as LaneConfigCollection; }
        }
    }

Now you can see that we have two properties with name PrimaryAgent and SecondaryAgent both have the same type now you can easily understand why we had only one implementation class against these two element.

Before you can use this newly invented configuration section in your app.config (or web.config) you just need to tell you application that you have invented your own configuration section and give it some respect, to do so you have to add following lines in app.config (may be right after start of root tag).

<configSections>
    <section name="CustomApplicationConfig" type="MyNameSpace.CustomApplicationConfigSection, MyAssemblyName" />
  </configSections>

NOTE: MyAssemblyName should be without .dll e.g. if you assembly file name is myDll.dll then use myDll instead of myDll.dll

to retrieve this configuration use following line of code any where in your application

CustomApplicationConfigSection config = System.Configuration.ConfigurationManager.GetSection(CustomApplicationConfigSection.SECTION_NAME) as CustomApplicationConfigSection;

I hope above post would help you to get started with a bit complicated kind of custom config sections.

Happy Coding :)

****Edit**** To Enable LINQ on LaneConfigCollection you have to implement IEnumerable<LaneConfigElement>

And Add following implementation of GetEnumerator

public new IEnumerator<LaneConfigElement> GetEnumerator()
        {
            int count = base.Count;
            for (int i = 0; i < count; i++)
            {
                yield return base.BaseGet(i) as LaneConfigElement;
            }
        }

for the people who are still confused about how yield really works read this nice article

Two key points taken from above article are

it doesn’t really end the method’s execution. yield return pauses the method execution and the next time you call it (for the next enumeration value), the method will continue to execute from the last yield return call. It sounds a bit confusing I think… (Shay Friedman)

Yield is not a feature of the .Net runtime. It is just a C# language feature which gets compiled into simple IL code by the C# compiler. (Lars Corneliussen)

Ionic 2: Cordova is not available. Make sure to include cordova.js or run in a device/simulator (running in emulator)

The livereload plugin fails to serve cordova.js file and serves // mock cordova file during development.

FIX: You need go to node_modules/@ionic/app-scripts/dist/dev-server/serve-config.js

and replace

exports.ANDROID_PLATFORM_PATH = path.join('platforms', 'android', 'assets', 'www');

to

exports.ANDROID_PLATFORM_PATH = path.join('platforms', 'android', 'app', 'src', 'main', 'assets', 'www');

How to connect to mysql with laravel?

You probably only forgot to create database. Enter your PHPMyAdmin and do it from there.

Edit: Definitely don't go with Maulik's answer. Not only it is using mysql_ extenstion (which is commonly recognized bad practice), Laravel is also taking care of your connections using PDO.

C error: undefined reference to function, but it IS defined

Add the "extern" keyword to the function definitions in point.h

Operation is not valid due to the current state of the object, when I select a dropdown list

I know an answer has already been accepted for this problem but someone asked in the comments if there was a solution that could be done outside the web.config. I had a ListView producing the exact same error and setting EnableViewState to false resolved this problem for me.

How to run a Python script in the background even after I logout SSH?

Here is a simple solution inside python using a decorator:

import os, time

def daemon(func):
    def wrapper(*args, **kwargs):
        if os.fork(): return
        func(*args, **kwargs)
        os._exit(os.EX_OK)
    return wrapper

@daemon
def my_func(count=10):    
  for i in range(0,count):
     print('parent pid: %d' % os.getppid())
     time.sleep(1)


my_func(count=10)
#still in parent thread
time.sleep(2)
#after 2 seconds the function my_func lives on is own

You can of course replace the content of your bgservice.py file in place of my_func.

Capturing TAB key in text box

I would advise against changing the default behaviour of a key. I do as much as possible without touching a mouse, so if you make my tab key not move to the next field on a form I will be very aggravated.

A shortcut key could be useful however, especially with large code blocks and nesting. Shift-TAB is a bad option because that normally takes me to the previous field on a form. Maybe a new button on the WMD editor to insert a code-TAB, with a shortcut key, would be possible?

How to select last two characters of a string

Slice can be used to find the substring. When we know the indexes we can use an alternative solution like index wise adder. Both are taking roughly the same time for execution.

_x000D_
_x000D_
const primitiveStringMember = "my name is Mate";

const objectStringMember = new String("my name is Mate");
console.log(typeof primitiveStringMember);//string
console.log(typeof objectStringMember);//object


/* However when we use . operator to string primitive type, JS will wrap up the string with object. That's why we can use the methods String object type for the primitive type string.
*/

//Slice method
const t0 = performance.now();
slicedString = primitiveStringMember.slice(-2);//te
const t1 = performance.now();
console.log(`Call to do slice took ${t1 - t0} milliseconds.`);


//index vise adder method
const t2 = performance.now();
length = primitiveStringMember.length
neededString = primitiveStringMember[length-2]+primitiveStringMember[length-1];//te
const t3 = performance.now();
console.log(`Call to do index adder took ${t3 - t2} milliseconds.`);
_x000D_
_x000D_
_x000D_

Mac OS X - EnvironmentError: mysql_config not found

If you don't want to install full mysql, we can fix this by just installing mysqlclient brew install mysqlclient Once cmd is completed it will ask to add below line to ~/.bash_profile:

echo 'export PATH="/usr/local/opt/mysql-client/bin:$PATH"' >> ~/.bash_profile

Close terminal and start new terminal and proceed with pip install mysqlclient

No mapping found for HTTP request with URI.... in DispatcherServlet with name

if you are using maven then do run maven install command before you run your web app on a server as it will generate a class file for your controller and in my experience that is what your application has been missing.

eslint: error Parsing error: The keyword 'const' is reserved

If using Visual Code one option is to add this to the settings.json file:

"eslint.options": {
    "useEslintrc": false,
    "parserOptions": {
        "ecmaVersion": 2017
    },
    "env": {
        "es6": true
    }
}

Closing Application with Exit button

You cannot exit your application. Using android.finish() won't exit the application, it just kills the activity. It's used when we don't want to see the previous activity on back button click. The application automatically exits when you switch off the device. The Android architecture does not support exiting the app. If you want, you can forcefully exit the app, but that's not considered good practice.

How do I find the parent directory in C#?

Since nothing else I have found helps to solve this in a truly normalized way, here is another answer.

Note that some answers to similar questions try to use the Uri type, but that struggles with trailing slashes vs. no trailing slashes too.

My other answer on this page works for operations that put the file system to work, but if we want to have the resolved path right now (such as for comparison reasons), without going through the file system, C:/Temp/.. and C:/ would be considered different. Without going through the file system, navigating in that manner does not provide us with a normalized, properly comparable path.

What can we do?

We will build on the following discovery:

Path.GetDirectoryName(path + "/") ?? "" will reliably give us a directory path without a trailing slash.

  • Adding a slash (as string, not as char) will treat a null path the same as it treats "".
  • GetDirectoryName will refrain from discarding the last path component thanks to the added slash.
  • GetDirectoryName will normalize slashes and navigational dots.
  • This includes the removal of any trailing slashes.
  • This includes collapsing .. by navigating up.
  • GetDirectoryName will return null for an empty path, which we coalesce to "".

How do we use this?

First, normalize the input path:

dirPath = Path.GetDirectoryName(dirPath + "/") ?? "";

Then, we can get the parent directory, and we can repeat this operation any number of times to navigate further up:

// This is reliable if path results from this or the previous operation
path = Path.GetDirectoryName(path);

Note that we have never touched the file system. No part of the path needs to exist, as it would if we had used DirectoryInfo.

Java SSL: how to disable hostname verification

There is no hostname verification in standard Java SSL sockets or indeed SSL, so that's why you can't set it at that level. Hostname verification is part of HTTPS (RFC 2818): that's why it manifests itself as javax.net.ssl.HostnameVerifier, which is applied to an HttpsURLConnection.

How do I cancel form submission in submit button onclick event?

You need to return false;:

<input type='submit' value='submit request' onclick='return btnClick();' />

function btnClick() {
    return validData();
}

Download old version of package with NuGet

Another option is to change the version number in the packages.config file. This will cause NuGet to download the dlls for that version the next time you build.

jQuery UI " $("#datepicker").datepicker is not a function"

I know that this post is quite old, but for reference I fixed this issue by updating the version of datepicker

It is worth trying that too to avoid hours of debugging.

https://cdnjs.com/libraries/bootstrap-datepicker

align divs to the bottom of their container

The modern way to do this is with flexbox, adding align-items: flex-end; on the container.

With this content:

<div class="Container">
  <div>one</div>
  <div>two</div>
</div>

Use this style:

.Container {
  display: flex;
  align-items: flex-end;
}

https://codepen.io/rds/pen/gGMBbg

Creating and returning Observable from Angular 2 Service

In the service.ts file -

a. import 'of' from observable/of
b. create a json list
c. return json object using Observable.of()
Ex. -

import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import { of } from 'rxjs/observable/of';

@Injectable()
export class ClientListService {
    private clientList;

    constructor() {
        this.clientList = [
            {name: 'abc', address: 'Railpar'},
            {name: 'def', address: 'Railpar 2'},
            {name: 'ghi', address: 'Panagarh'},
            {name: 'jkl', address: 'Panagarh 2'},
        ];
    }

    getClientList () {
        return Observable.of(this.clientList);
    }
};

In the component where we are calling the get function of the service -

this.clientListService.getClientList().subscribe(res => this.clientList = res);

Test if number is odd or even

You were right in thinking mod was a good place to start. Here is an expression which will return true if $number is even, false if odd:

$number % 2 == 0

Works for every integerPHP value, see as well Arithmetic OperatorsPHP.

Example:

$number = 20;
if ($number % 2 == 0) {
  print "It's even";
}

Output:

It's even

how to replace characters in hive?

Custom SerDe might be a way to do it. Or you could use some kind of mediation process with regex_replace:

create table tableB as 
select 
    columnA
    regexp_replace(description, '\\t', '') as description
from tableA
;

What is so bad about singletons?

Monopoly is the devil and singletons with non-readonly/mutable state are the 'real' problem...

After reading Singletons are Pathological Liars as suggested in jason's answer I came across this little tidbit that provides the best presented example of how singletons are often misused.

Global is bad because:

  • a. It causes namespace conflict
  • b. It exposes the state in a unwarranted fashion

When it comes to Singletons

  • a. The explicit OO way of calling them, prevents the conflicts, so point a. is not an issue
  • b. Singletons without state are (like factories) are not a problem. Singletons with state can again fall in two categories, those which are immutable or write once and read many (config/property files). These are not bad. Mutable Singletons, which are kind of reference holders are the ones which you are speaking of.

In the last statement he's referring to the blog's concept of 'singletons are liars'.

How does this apply to Monopoly?

To start a game of monopoly, first:

  • we establish the rules first so everybody is on the same page
  • everybody is given an equal start at the beginning of the game
  • only one set of rules is presented to avoid confusion
  • the rules aren't allowed to change throughout the game

Now, for anybody who hasn't really played monopoly, these standards are ideal at best. A defeat in monopoly is hard to swallow because, monopoly is about money, if you lose you have to painstakingly watch the rest of the players finish the game, and losses are usually swift and crushing. So, the rules usually get twisted at some point to serve the self-interest of some of the players at the expense of the others.

So you're playing monopoly with friends Bob, Joe, and Ed. You're swiftly building your empire and consuming market share at an exponential rate. Your opponents are weakening and you start to smell blood (figuratively). Your buddy Bob put all of his money into gridlocking as many low-value properties as possible but his isn't receiving a high return on investment the way he expected. Bob, as a stroke of bad luck, lands on your Boardwalk and is excised from the game.

Now the game goes from friendly dice-rolling to serious business. Bob has been made the example of failure and Joe and Ed don't want to end up like 'that guy'. So, being the leading player you, all of a sudden, become the enemy. Joe and Ed start practicing under-the-table trades, behind-the-back money injections, undervalued house-swapping and generally anything to weaken you as a player until one of them rises to the top.

Then, instead of one of them winning, the process starts all over. All of a sudden, a finite set of rules becomes a moving target and the game degenerates into the type of social interactions that would make up the foundation of every high-rated reality TV show since Survivor. Why, because the rules are changing and there's no consensus on how/why/what they're supposed to represent, and more importantly, there's no one person making the decisions. Every player in the game, at that point, is making his/her own rules and chaos ensues until two of the players are too tired to keep up the charade and slowly give up.

So, if a rulebook for a game accurately represented a singleton, the monopoly rulebook would be an example of abuse.

How does this apply to programming?

Aside from all of the obvious thread-safety and synchronization issues that mutable singletons present... If you have one set of data, that is capable of being read/manipulated by multiple different sources concurrently and exists during the lifetime of the application execution, it's probably a good time to step back and ask "am I using the right type of data structure here".

Personally, I have seen a programmer abuse a singleton by using it as some sort of twisted cross-thread database store within an application. Having worked on the code directly, I can attest that it was a slow (because of all the thread locks needed to make it thread-safe) and a nightmare to work on (because of the unpredictable/intermittent nature of synchronization bugs), and nearly impossible to test under 'production' conditions. Sure, a system could have been developed using polling/signaling to overcome some of the performance issues but that wouldn't solve the issues with testing and, why bother when a 'real' database can already accomplish the same functionality in a much more robust/scalable manner.

A Singleton is only an option if you need what a singleton provides. A write-one read-only instance of an object. That same rule should cascade to the object's properties/members as well.

How to import component into another root component in Angular 2

For Angular RC5 and RC6 you have to declare component in the module metadata decorator's declarations key, so add CoursesComponent in your main module declarations as below and remove directives from AppComponent metadata.

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent } from './app.component';
import { CoursesComponent } from './courses.component';

@NgModule({
  imports:      [ BrowserModule ],
  declarations: [ AppComponent, CoursesComponent ],
  bootstrap:    [ AppComponent ]
})
export class AppModule { }

SignalR - Sending a message to a specific user using (IUserIdProvider) *NEW 2.0.0*

SignalR provides ConnectionId for each connection. To find which connection belongs to whom (the user), we need to create a mapping between the connection and the user. This depends on how you identify a user in your application.

In SignalR 2.0, this is done by using the inbuilt IPrincipal.Identity.Name, which is the logged in user identifier as set during the ASP.NET authentication.

However, you may need to map the connection with the user using a different identifier instead of using the Identity.Name. For this purpose this new provider can be used with your custom implementation for mapping user with the connection.

Example of Mapping SignalR Users to Connections using IUserIdProvider

Lets assume our application uses a userId to identify each user. Now, we need to send message to a specific user. We have userId and message, but SignalR must also know the mapping between our userId and the connection.

To achieve this, first we need to create a new class which implements IUserIdProvider:

public class CustomUserIdProvider : IUserIdProvider
{
     public string GetUserId(IRequest request)
    {
        // your logic to fetch a user identifier goes here.

        // for example:

        var userId = MyCustomUserClass.FindUserId(request.User.Identity.Name);
        return userId.ToString();
    }
}

The second step is to tell SignalR to use our CustomUserIdProvider instead of the default implementation. This can be done in the Startup.cs while initializing the hub configuration:

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        var idProvider = new CustomUserIdProvider();

        GlobalHost.DependencyResolver.Register(typeof(IUserIdProvider), () => idProvider);          

        // Any connection or hub wire up and configuration should go here
        app.MapSignalR();
    }
}

Now, you can send message to a specific user using his userId as mentioned in the documentation, like:

public class MyHub : Hub
{
   public void Send(string userId, string message)
   {
      Clients.User(userId).send(message);
   }
}

Hope this helps.

R cannot be resolved - Android error

This could be an issue caused by manually renaming the package in the AndroidManifest.xml

An alternative is to use the built in tool to rename the package, this will take care of most of the problems avoiding the R not found issue.

Right Click on the project
Click on Android Tools
Click on Rename Application Project
Enter the new package name

Then a pop-up will appear asking for changes to be applied, including the R workaround.

Source: Rename package name in android

C# Enum - How to Compare Value

You can use extension methods to do the same thing with less code.

public enum AccountType
{
    Retailer = 1,
    Customer = 2,
    Manager = 3,
    Employee = 4
}

static class AccountTypeMethods
{
    public static bool IsRetailer(this AccountType ac)
    {
        return ac == AccountType.Retailer;
    }
}

And to use:

if (userProfile.AccountType.isRetailer())
{
    //your code
}

I would recommend to rename the AccountType to Account. It's not a name convention.

Slicing a dictionary

You should be iterating over the tuple and checking if the key is in the dict not the other way around, if you don't check if the key exists and it is not in the dict you are going to get a key error:

print({k:d[k] for k in l if k in d})

Some timings:

 {k:d[k] for k in set(d).intersection(l)}

In [22]: %%timeit                        
l = xrange(100000)
{k:d[k] for k in l}
   ....: 
100 loops, best of 3: 11.5 ms per loop

In [23]: %%timeit                        
l = xrange(100000)
{k:d[k] for k in set(d).intersection(l)}
   ....: 
10 loops, best of 3: 20.4 ms per loop

In [24]: %%timeit                        
l = xrange(100000)
l = set(l)                              
{key: d[key] for key in d.viewkeys() & l}
   ....: 
10 loops, best of 3: 24.7 ms per

In [25]: %%timeit                        

l = xrange(100000)
{k:d[k] for k in l if k in d}
   ....: 
100 loops, best of 3: 17.9 ms per loop

I don't see how {k:d[k] for k in l} is not readable or elegant and if all elements are in d then it is pretty efficient.

How can I use onItemSelected in Android?

For Kotlin and bindings the code is:

binding.spinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener{
            override fun onNothingSelected(parent: AdapterView<*>?) {
            }

            override fun onItemSelected(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {
            }
        }

How do I find files that do not contain a given string pattern?

Take a look at ack. It does the .svn exclusion for you automatically, gives you Perl regular expressions, and is a simple download of a single Perl program.

The equivalent of what you're looking for should be, in ack:

ack -L foo

Why does JS code "var a = document.querySelector('a[data-a=1]');" cause error?

Took me a while to find this out but if you a number stored in a variable, say x and you want to select it, use

document.querySelector('a[data-a= + CSS.escape(x) + ']'). 

This is due to some attribute naming specifications that I'm not yet very familiar with. Hope this will help someone.

TLS 1.2 in .NET Framework 4.0

There are two possible scenarios,

  1. If your application runs on .net framework 4.5 or less, and you can easily deploy new code to the production then you can use of below solution.

    You can add the below line of code before making the API call,

    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12; // .NET 4.5
    ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072; // .NET 4.0
    
  2. If you cannot deploy new code and you want to resolve the issue with the same code which is present in the production, then you have two options.

Option 1 :

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319]
"SchUseStrongCrypto"=dword:00000001


then create a file with extension .reg and install.

Note : This setting will apply at registry level and is applicable to all application present on that machine and if you want to restrict to only single application then you can use Option 2

Option 2 : This can be done by changing some configuration setting in config file. You can add either in your config file.

<runtime>
    <AppContextSwitchOverrides value="Switch.System.Net.DontEnableSchUseStrongCrypto=false"/>
</runtime>

or

<runtime>
  <AppContextSwitchOverrides value="Switch.System.Net.DontEnableSystemDefaultTlsVersions=false"
</runtime>

how to send a post request with a web browser

with a form, just set method to "post"

<form action="blah.php" method="post">
  <input type="text" name="data" value="mydata" />
  <input type="submit" />
</form>

Using Rsync include and exclude options to include directory and file by pattern

Here's my "teach a person to fish" answer:

Rsync's syntax is definitely non-intuitive, but it is worth understanding.

  1. First, use -vvv to see the debug info for rsync.
$ rsync -nr -vvv --include="**/file_11*.jpg" --exclude="*" /Storage/uploads/ /website/uploads/

[sender] hiding directory 1280000000 because of pattern *
[sender] hiding directory 1260000000 because of pattern *
[sender] hiding directory 1270000000 because of pattern *

The key concept here is that rsync applies the include/exclude patterns for each directory recursively. As soon as the first include/exclude is matched, the processing stops.

The first directory it evaluates is /Storage/uploads. Storage/uploads has 1280000000/, 1260000000/, 1270000000/ dirs/files. None of them match file_11*.jpg to include. All of them match * to exclude. So they are excluded, and rsync ends.

  1. The solution is to include all dirs (*/) first. Then the first dir component will be 1260000000/, 1270000000/, 1280000000/ since they match */. The next dir component will be 1260000000/. In 1260000000/, file_11_00.jpg matches --include="file_11*.jpg", so it is included. And so forth.
$ rsync -nrv --include='*/' --include="file_11*.jpg" --exclude="*" /Storage/uploads/ /website/uploads/

./
1260000000/
1260000000/file_11_00.jpg
1260000000/file_11_01.jpg
1270000000/
1270000000/file_11_00.jpg
1270000000/file_11_01.jpg
1280000000/
1280000000/file_11_00.jpg
1280000000/file_11_01.jpg

https://download.samba.org/pub/rsync/rsync.1

What's the difference between getRequestURI and getPathInfo methods in HttpServletRequest?

getPathInfo() gives the extra path information after the URI, used to access your Servlet, where as getRequestURI() gives the complete URI.

I would have thought they would be different, given a Servlet must be configured with its own URI pattern in the first place; I don't think I've ever served a Servlet from root (/).

For example if Servlet 'Foo' is mapped to URI '/foo' then I would have thought the URI:

/foo/path/to/resource

Would result in:

RequestURI = /foo/path/to/resource

and

PathInfo = /path/to/resource

Set EditText cursor color

After a lot of time spent trying all these technique in a Dialog, I finally had this idea : attach the theme to the Dialog itself and not to the TextInputLayout.

<style name="AppTheme_Dialog" parent="Theme.AppCompat.Dialog">

    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorWhite</item>
    <item name="colorAccent">@color/colorPrimary</item>

</style>

inside onCreate :

public class myDialog extends Dialog {

private Activity activity;
private someVars;

public PopupFeedBack(Activity activity){
    super(activity, R.style.AppTheme_Dialog);
    setContentView(R.layout.myView);
    ....}}

cheers :)

Tools for creating Class Diagrams

I have used both Poseidon UML and Enterprise Architect and must say that I prefer Poseidon but wasn't fully satisfied with any of them.

How to Determine the Screen Height and Width in Flutter

Just declare a function

Size screenSize() {
return MediaQuery.of(context).size;
}

Use like below

return Container(
      width: screenSize().width,
      height: screenSize().height,
      child: ...
 )

Why should a Java class implement comparable?

Comparable is used to compare instances of your class. We can compare instances from many ways that is why we need to implement a method compareTo in order to know how (attributes) we want to compare instances.

Dog class:

package test;
import java.util.Arrays;

public class Main {

    public static void main(String[] args) {
        Dog d1 = new Dog("brutus");
        Dog d2 = new Dog("medor");
        Dog d3 = new Dog("ara");
        Dog[] dogs = new Dog[3];
        dogs[0] = d1;
        dogs[1] = d2;
        dogs[2] = d3;

        for (int i = 0; i < 3; i++) {
            System.out.println(dogs[i].getName());
        }
        /**
         * Output:
         * brutus
         * medor
         * ara
         */

        Arrays.sort(dogs, Dog.NameComparator);
        for (int i = 0; i < 3; i++) {
            System.out.println(dogs[i].getName());
        }
        /**
         * Output:
         * ara
         * medor
         * brutus
         */

    }
}

Main class:

package test;

import java.util.Arrays;

public class Main {

    public static void main(String[] args) {
        Dog d1 = new Dog("brutus");
        Dog d2 = new Dog("medor");
        Dog d3 = new Dog("ara");
        Dog[] dogs = new Dog[3];
        dogs[0] = d1;
        dogs[1] = d2;
        dogs[2] = d3;

        for (int i = 0; i < 3; i++) {
            System.out.println(dogs[i].getName());
        }
        /**
         * Output:
         * brutus
         * medor
         * ara
         */

        Arrays.sort(dogs, Dog.NameComparator);
        for (int i = 0; i < 3; i++) {
            System.out.println(dogs[i].getName());
        }
        /**
         * Output:
         * ara
         * medor
         * brutus
         */

    }
}

Here is a good example how to use comparable in Java:

http://www.onjava.com/pub/a/onjava/2003/03/12/java_comp.html?page=2

How can I make a time delay in Python?

import time
time.sleep(5)   # Delays for 5 seconds. You can also use a float value.

Here is another example where something is run approximately once a minute:

import time
while True:
    print("This prints once a minute.")
    time.sleep(60) # Delay for 1 minute (60 seconds).

mongodb service is not starting up

For ubunto , what made it happen and was real simple is to install mongodb package:

sudo apt-get install  mongodb

Interface vs Base class

Make a list of the things your objects must be, have, or do and the things your objects can (or might) be, have, or do. Must indicates your base types and can indicates your interfaces.

E.g., your PetBase must Breathe, and your IPet might DoTricks.

Analysis of your problem domain will help you define the precise hierarchy structure.

Java double comparison epsilon

Yes. Java doubles will hold their precision better than your given epsilon of 0.00001.

Any rounding error that occurs due to the storage of floating point values will occur smaller than 0.00001. I regularly use 1E-6 or 0.000001 for a double epsilon in Java with no trouble.

On a related note, I like the format of epsilon = 1E-5; because I feel it is more readable (1E-5 in Java = 1 x 10^-5). 1E-6 is easy to distinguish from 1E-5 when reading code whereas 0.00001 and 0.000001 look so similar when glancing at code I think they are the same value.

Integer to hex string in C++

For those of you who figured out that many/most of the ios::fmtflags don't work with std::stringstream yet like the template idea that Kornel posted way back when, the following works and is relatively clean:

#include <iomanip>
#include <sstream>


template< typename T >
std::string hexify(T i)
{
    std::stringbuf buf;
    std::ostream os(&buf);


    os << "0x" << std::setfill('0') << std::setw(sizeof(T) * 2)
       << std::hex << i;

    return buf.str().c_str();
}


int someNumber = 314159265;
std::string hexified = hexify< int >(someNumber);

Closing Twitter Bootstrap Modal From Angular Controller

You can do it like this:

angular.element('#modal').modal('hide');

The way to check a HDFS directory's size?

When trying to calculate the total of a particular group of files within a directory the -s option does not work (in Hadoop 2.7.1). For example:

Directory structure:

some_dir
+abc.txt    
+count1.txt 
+count2.txt 
+def.txt    

Assume each file is 1 KB in size. You can summarize the entire directory with:

hdfs dfs -du -s some_dir
4096 some_dir

However, if I want the sum of all files containing "count" the command falls short.

hdfs dfs -du -s some_dir/count*
1024 some_dir/count1.txt
1024 some_dir/count2.txt

To get around this I usually pass the output through awk.

hdfs dfs -du some_dir/count* | awk '{ total+=$1 } END { print total }'
2048 

SQL "select where not in subquery" returns no results

I had an example where I was looking up and because one table held the value as a double, the other as a string, they would not match (or not match without a cast). But only NOT IN. As SELECT ... IN ... worked. Weird, but thought I would share in case anyone else encounters this simple fix.

Why is Ant giving me a Unsupported major.minor version error

Simply just check your run time by go to ant build configuration and change the jre against to jdk (if jdk 1.7 then jre should be 1.7) .

enter image description here

OperationalError, no such column. Django

I think you skipped this steps...run the following commands to see if you had forgotten to execute them...it worked for me.

$ python manage.py makemigrations

$ python manage.py migrate

Thank you.

Why can't I make a vector of references?

As other have mentioned, you will probably end up using a vector of pointers instead.

However, you may want to consider using a ptr_vector instead!

WPF What is the correct way of using SVG files as icons in WPF

Use the SvgImage or the SvgImageConverter extensions, the SvgImageConverter supports binding. See the following link for samples demonstrating both extensions.

https://github.com/ElinamLLC/SharpVectors/tree/master/TutorialSamples/ControlSamplesWpf

Write a mode method in Java to find the most frequently occurring element in an array

You should be able to do this in N operations, meaning in just one pass, O(n) time.

Use a map or int[] (if the problem is only for ints) to increment the counters, and also use a variable that keeps the key which has the max count seen. Everytime you increment a counter, ask what the value is and compare it to the key you used last, if the value is bigger update the key.

public class Mode {
public static int mode(final int[] n) {
    int maxKey = 0;
    int maxCounts = 0;

    int[] counts = new int[n.length];

    for (int i=0; i < n.length; i++) {
        counts[n[i]]++;
        if (maxCounts < counts[n[i]]) {
            maxCounts = counts[n[i]];
            maxKey = n[i];
        }
    }
    return maxKey;
}

public static void main(String[] args) {
    int[] n = new int[] { 3,7,4,1,3,8,9,3,7,1 };
    System.out.println(mode(n));
}
}

Determine the path of the executing BASH script

For the relative path (i.e. the direct equivalent of Windows' %~dp0):

MY_PATH="`dirname \"$0\"`"
echo "$MY_PATH"

For the absolute, normalized path:

MY_PATH="`dirname \"$0\"`"              # relative
MY_PATH="`( cd \"$MY_PATH\" && pwd )`"  # absolutized and normalized
if [ -z "$MY_PATH" ] ; then
  # error; for some reason, the path is not accessible
  # to the script (e.g. permissions re-evaled after suid)
  exit 1  # fail
fi
echo "$MY_PATH"

submit a form in a new tab

Try using jQuery

<script type="text/javascript">
$("form").submit(function() {
$("form").attr('target', '_blank');
return true;
});
</script>

Here is a full answer - http://ftutorials.com/open-html-form-in-new-tab/

How to convert a Title to a URL slug in jQuery?

You may want to take a look at the speakingURL plugin and then you just could:

    $("#Restaurant_Name").on("keyup", function () {
        var slug = getSlug($("#Restaurant_Name").val());
        $("#Restaurant_Slug").val(slug);
    });

Getting HTML elements by their attribute names

You can use querySelectorAll:

    document.querySelectorAll('span[property=name]');

How to move up a directory with Terminal in OS X

For Mac Terminal

cd ..   # one up
cd ../  # two up
cd      # home directory 
cd /    # root directory
cd "yaya-13" # use quotes if the file name contains punctuation or spaces

Auto number column in SharePoint list

it's in there by default. It's the id field.

Excel - Combine multiple columns into one column

Try this. Click anywhere in your range of data and then use this macro:

Sub CombineColumns()
Dim rng As Range
Dim iCol As Integer
Dim lastCell As Integer

Set rng = ActiveCell.CurrentRegion
lastCell = rng.Columns(1).Rows.Count + 1

For iCol = 2 To rng.Columns.Count
    Range(Cells(1, iCol), Cells(rng.Columns(iCol).Rows.Count, iCol)).Cut
    ActiveSheet.Paste Destination:=Cells(lastCell, 1)
    lastCell = lastCell + rng.Columns(iCol).Rows.Count
Next iCol
End Sub

Can't Autowire @Repository annotated interface in Spring Boot

Sometimes I had the same issues when I forget to add Lombok annotation processor dependency to the maven configuration

Breaking out of a nested loop

Sometimes nice to abstract the code into it's own function and than use an early return - early returns are evil though : )

public void GetIndexOf(Transform transform, out int outX, out int outY)
{
    outX = -1;
    outY = -1;

    for (int x = 0; x < Columns.Length; x++)
    {
        var column = Columns[x];

        for (int y = 0; y < column.Transforms.Length; y++)
        {
            if(column.Transforms[y] == transform)
            {
                outX = x;
                outY = y;

                return;
            }
        }
    }
}

Getting char from string at specified index

Getting one char from string at specified index

Dim pos As Integer
Dim outStr As String
pos = 2 
Dim outStr As String
outStr = Left(Mid("abcdef", pos), 1)

outStr="b"

How to get substring from string in c#?

string text = "Retrieves a substring from this instance. The substring starts at a specified character position. Some other text";

string result = text.Substring(text.IndexOf('.') + 1,text.LastIndexOf('.')-text.IndexOf('.'))

This will cut the part of string which lays between the special characters.

How do I close a tkinter window?

You can use:

root.destroy()

Or

root.quit()

If that does not work, change root to what ever your variable was at the start of your program

import tkinter

main = Tk()

main.destroy()

main.mainloop

Dump a list in a pickle file and retrieve it back later

Pickling will serialize your list (convert it, and it's entries to a unique byte string), so you can save it to disk. You can also use pickle to retrieve your original list, loading from the saved file.

So, first build a list, then use pickle.dump to send it to a file...

Python 3.4.1 (default, May 21 2014, 12:39:51) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> mylist = ['I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.', "Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?", "I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!", "No, no, 'e's uh,...he's resting."]
>>> 
>>> import pickle
>>> 
>>> with open('parrot.pkl', 'wb') as f:
...   pickle.dump(mylist, f)
... 
>>> 

Then quit and come back later… and open with pickle.load...

Python 3.4.1 (default, May 21 2014, 12:39:51) 
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> with open('parrot.pkl', 'rb') as f:
...   mynewlist = pickle.load(f)
... 
>>> mynewlist
['I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.', "Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?", "I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!", "No, no, 'e's uh,...he's resting."]
>>>

What are the file limits in Git (number and size)?

I think that it's good to try to avoid large file commits as being part of the repository (e.g. a database dump might be better off elsewhere), but if one considers the size of the kernel in its repository, you can probably expect to work comfortably with anything smaller in size and less complex than that.

Adding an image to a PDF using iTextSharp and scale it properly

image.ScaleToFit(500f,30f);

this method keeps the aspect ratio of the image

Use RSA private key to generate public key?

here in this code first we are creating RSA key which is private but it has pair of its public key as well so to get your actual public key we simply do this

openssl rsa -in mykey.pem -pubout > mykey.pub

hope you get it for more info check this

Method List in Visual Studio Code

In 2020 version of VSCode
Cmd+P

  • # - Find symbol across files
  • @ - Find symbol within file
  • @: - Group symbols within a file

Symbols in a file VS Code v1.44.0

Constructors in Go

In Go, a constructor can be implemented using a function that returns a pointer to a modified structure.

type Colors struct {
    R   byte
    G   byte
    B   byte
}

// Constructor
func NewColors (r, g, b byte) *Colors {
    return &Color{R:r, G:g, B:b}
}

For weak dependencies and better abstraction, the constructor does not return a pointer to a structure, but an interface that this structure implements.

type Painter interface {
    paintMethod1() byte
    paintMethod2(byte) byte
}

type Colors struct {
    R byte
    G byte
    B byte
}

// Constructor return intreface
func NewColors(r, g, b byte) Painter {
    return &Color{R: r, G: g, B: b}
}

func (c *Colors) paintMethod1() byte {
    return c.R
}

func (c *Colors) paintMethod2(b byte) byte {
    return c.B = b
}

Pandas: convert dtype 'object' to int

Follow these steps:

1.clean your file -> open your datafile in csv format and see that there is "?" in place of empty places and delete all of them.

2.drop the rows containing missing values e.g.:

df.dropna(subset=["normalized-losses"], axis = 0 , inplace= True)

3.use astype now for conversion

df["normalized-losses"]=df["normalized-losses"].astype(int)

Note: If still finding erros in your program then again inspect your csv file, open it in excel to find whether is there an "?" in your required column, then delete it and save file and go back and run your program.

comment success! if it works. :)

Render partial view with dynamic model in Razor view engine and ASP.NET MVC 3

I had the same problem & in my case this is what I did

@Html.Partial("~/Views/Cabinets/_List.cshtml", (List<Shop>)ViewBag.cabinets)

and in Partial view

@foreach (Shop cabinet in Model)
{
    //...
}

How can I delete one element from an array by value

You can also monkey patch it. I never understood why Ruby has an except method for Hash but not for Array:

class Array
  def except value
    value = value.kind_of(Array) ? value : [value]
    self - value
  end
end

Now you can do:

[1,3,7,"436",354,nil].except(354) #=> [1,3,7,"436",nil]

Or:

[1,3,7,"436",354,nil].except([354, 1]) #=> [3,7,"436",nil]

Gradle Sync failed could not find constraint-layout:1.0.0-alpha2

Just as a heads up to those still searching for this.

ConstraintLayout 1.0.1 and lower have been deprecated by maven.

For a list of available constraint layouts that can be downloaded, see below:

https://maven.google.com/web/index.html?q=Constrain#com.android.support.constraint:constraint-layout

The easiest solution at the moment, is to change

implementation 'com.android.support.constraint:constraint-layout:1.0.0-beta1'

to

implementation 'com.android.support.constraint:constraint-layout:1.0.2'

Most efficient way to find smallest of 3 numbers Java?

Simply use this math function

System.out.println(Math.min(a,b,c));

You will get the answer in single line.

how can I debug a jar at runtime?

With IntelliJ IDEA you can create a Jar Application runtime configuration, select the JAR, the sources, the JRE to run the Jar with and start debugging. Here is the documentation.

Get the last 4 characters of a string

str = "aaaaabbbb"
newstr = str[-4:]

See : http://codepad.org/S3zjnKoD

Finding the index of elements based on a condition using python list comprehension

Even if it's a late answer: I think this is still a very good question and IMHO Python (without additional libraries or toolkits like numpy) is still lacking a convenient method to access the indices of list elements according to a manually defined filter.

You could manually define a function, which provides that functionality:

def indices(list, filtr=lambda x: bool(x)):
    return [i for i,x in enumerate(list) if filtr(x)]

print(indices([1,0,3,5,1], lambda x: x==1))

Yields: [0, 4]

In my imagination the perfect way would be making a child class of list and adding the indices function as class method. In this way only the filter method would be needed:

class MyList(list):
    def __init__(self, *args):
        list.__init__(self, *args)
    def indices(self, filtr=lambda x: bool(x)):
        return [i for i,x in enumerate(self) if filtr(x)]

my_list = MyList([1,0,3,5,1])
my_list.indices(lambda x: x==1)

I elaborated a bit more on that topic here: http://tinyurl.com/jajrr87

How to set corner radius of imageView?

in swift 3 'CGRectGetWidth' has been replaced by property 'CGRect.width'

    view.layer.cornerRadius = view.frame.width/4.0
    view.clipsToBounds = true

How to pass List from Controller to View in MVC 3

  1. Create a model which contains your list and other things you need for the view.

    For example:

    public class MyModel
    {
        public List<string> _MyList { get; set; }
    }
    
  2. From the action method put your desired list to the Model, _MyList property, like:

    public ActionResult ArticleList(MyModel model)
    {
        model._MyList = new List<string>{"item1","item2","item3"};
        return PartialView(@"~/Views/Home/MyView.cshtml", model);
    }
    
  3. In your view access the model as follows

    @model MyModel
    foreach (var item in Model)
    {
       <div>@item</div>
    }
    

I think it will help for start.

.gitignore all the .DS_Store files in every folder and subfolder

You should add following lines while creating a project. It will always ignore .DS_Store to be pushed to the repository.

*.DS_Store this will ignore .DS_Store while code commit.
git rm --cached .DS_Store this is to remove .DS_Store files from your repository, in case you need it, you can uncomment it.

## ignore .DS_Store file.
# git rm --cached .DS_Store
*.DS_Store

Can I delete data from the iOS DeviceSupport directory?

Yes, you can delete data from iOS device support by the symbols of the operating system, one for each version for each architecture. It's used for debugging. If you don't need to support those devices any more, you can delete the directory without ill effect

PostgreSQL: Why psql can't connect to server?

In my case I had this error, /var/run/postgresql/.s.PGSQL.5433 (note, one number up from the file it was looking for, .s.PGSQL.5432) was present. Tried the instructions at the top of this page but nothing worked.

Turns out there was an old directory for PostGreSQL 12 config files in /etc/postgresql/12, which I deleted, which solved the issue.

Java parsing XML document gives "Content not allowed in prolog." error

If you're able to control the xml file, try adding a bit more information to the beginning of the file:

<?xml version="1.0" encoding="UTF-16" standalone="no"?>

How to top, left justify text in a <td> cell that spans multiple rows

td[rowspan] {
  vertical-align: top;
  text-align: left;
}

See: CSS attribute selectors.

How to click on hidden element in Selenium WebDriver?

First store that element in object, let's say element and then write following code to click on that hidden element:

JavascriptExecutor js = (JavascriptExecutor)driver;
js.executeScript("arguments[0].click();", element);

Android Studio-No Module

I had the same issue since I changed my app ID in config.xml file.

I used to open my Android project by choosing among recent projects of Android Studio.

I just File > Open > My project to get it working again.

How can I hide an HTML table row <tr> so that it takes up no space?

This happened to me and I was baffled as to why. Then I noticed that if i removed any nbsp; i had within the rows, then the rows didn't take up any space.

How do I stretch a background image to cover the entire HTML element?

You cannot in pure CSS. Having an image covering the whole page behind all other components is probably your best bet (looks like that's the solution given above). Anyway, chances are it will look awful anyway. I would try either an image big enough to cover most screen resolutions (say up to 1600x1200, above it is scarcer), to limit the width of the page, or just to use an image that tile.

Search of table names

I'm using this and works fine

SELECT * FROM INFORMATION_SCHEMA.TABLES 
WHERE TABLE_NAME LIKE '%%'

Add/delete row from a table

Here's the code JS Bin using jQuery. Tested on all the browsers. Here, we have to click the rows in order to delete it with beautiful effect. Hope it helps.

Open source PDF library for C/C++ application?

It depends a bit on your needs. Some toolkits are better at drawing, others are better for writing text. Cairo has a pretty good for drawing (it support a wide range of screen and file types, including pdf), but it may not be ideal for good typography.

How to use range-based for() loop with std::map?

Each element of the container is a map<K, V>::value_type, which is a typedef for std::pair<const K, V>. Consequently, in C++17 or higher, you can write

for (auto& [key, value]: myMap) {
    std::cout << key << " has value " << value << std::endl;
}

or as

for (const auto& [key, value]: myMap) {
    std::cout << key << " has value " << value << std::endl;
}

if you don't plan on modifying the values.

In C++11 and C++14, you can use enhanced for loops to extract out each pair on its own, then manually extract the keys and values:

for (const auto& kv : myMap) {
    std::cout << kv.first << " has value " << kv.second << std::endl;
}

You could also consider marking the kv variable const if you want a read-only view of the values.

MatPlotLib: Multiple datasets on the same scatter plot

You can also do this easily in Pandas, if your data is represented in a Dataframe, as described here:

http://pandas.pydata.org/pandas-docs/version/0.15.0/visualization.html#scatter-plot

How can I add some small utility functions to my AngularJS application?

Do I understand correctly that you just want to define some utility methods and make them available in templates?

You don't have to add them to every controller. Just define a single controller for all the utility methods and attach that controller to <html> or <body> (using the ngController directive). Any other controllers you attach anywhere under <html> (meaning anywhere, period) or <body> (anywhere but <head>) will inherit that $scope and will have access to those methods.

g++ undefined reference to typeinfo

This can also happen when you mix -fno-rtti and -frtti code. Then you need to ensure that any class, which type_info is accessed in the -frtti code, have their key method compiled with -frtti. Such access can happen when you create an object of the class, use dynamic_cast etc.

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