Programs & Examples On #Lazy evaluation

Lazy evaluation refers to a variety of concepts that seek to avoid evaluation of an expression unless its value is needed, and to share the results of evaluation of an expression among all uses of its, so that no expression need be evaluated more than once.

When should I use Lazy<T>?

You should try to avoid using Singletons, but if you ever do need to, Lazy<T> makes implementing lazy, thread-safe singletons easy:

public sealed class Singleton
{
    // Because Singleton's constructor is private, we must explicitly
    // give the Lazy<Singleton> a delegate for creating the Singleton.
    static readonly Lazy<Singleton> instanceHolder =
        new Lazy<Singleton>(() => new Singleton());

    Singleton()
    {
        // Explicit private constructor to prevent default public constructor.
        ...
    }

    public static Singleton Instance => instanceHolder.Value;
}

Read a file one line at a time in node.js?

function createLineReader(fileName){
    var EM = require("events").EventEmitter
    var ev = new EM()
    var stream = require("fs").createReadStream(fileName)
    var remainder = null;
    stream.on("data",function(data){
        if(remainder != null){//append newly received data chunk
            var tmp = new Buffer(remainder.length+data.length)
            remainder.copy(tmp)
            data.copy(tmp,remainder.length)
            data = tmp;
        }
        var start = 0;
        for(var i=0; i<data.length; i++){
            if(data[i] == 10){ //\n new line
                var line = data.slice(start,i)
                ev.emit("line", line)
                start = i+1;
            }
        }
        if(start<data.length){
            remainder = data.slice(start);
        }else{
            remainder = null;
        }
    })

    stream.on("end",function(){
        if(null!=remainder) ev.emit("line",remainder)
    })

    return ev
}


//---------main---------------
fileName = process.argv[2]

lineReader = createLineReader(fileName)
lineReader.on("line",function(line){
    console.log(line.toString())
    //console.log("++++++++++++++++++++")
})

What does a lazy val do?

scala> lazy val lazyEight = {
     |   println("I am lazy !")
     |   8
     | }
lazyEight: Int = <lazy>

scala> lazyEight
I am lazy !
res1: Int = 8
  • All vals are initialized during object construction
  • Use lazy keyword to defer initialization until first usage
  • Attention: Lazy vals are not final and therefore might show performance drawbacks

ASP.NET MVC 404 Error Handling

The response from Marco is the BEST solution. I needed to control my error handling, and I mean really CONTROL it. Of course, I have extended the solution a little and created a full error management system that manages everything. I have also read about this solution in other blogs and it seems very acceptable by most of the advanced developers.

Here is the final code that I am using:

protected void Application_EndRequest()
    {
        if (Context.Response.StatusCode == 404)
        {
            var exception = Server.GetLastError();
            var httpException = exception as HttpException;
            Response.Clear();
            Server.ClearError();
            var routeData = new RouteData();
            routeData.Values["controller"] = "ErrorManager";
            routeData.Values["action"] = "Fire404Error";
            routeData.Values["exception"] = exception;
            Response.StatusCode = 500;

            if (httpException != null)
            {
                Response.StatusCode = httpException.GetHttpCode();
                switch (Response.StatusCode)
                {
                    case 404:
                        routeData.Values["action"] = "Fire404Error";
                        break;
                }
            }
            // Avoid IIS7 getting in the middle
            Response.TrySkipIisCustomErrors = true;
            IController errormanagerController = new ErrorManagerController();
            HttpContextWrapper wrapper = new HttpContextWrapper(Context);
            var rc = new RequestContext(wrapper, routeData);
            errormanagerController.Execute(rc);
        }
    }

and inside my ErrorManagerController :

        public void Fire404Error(HttpException exception)
    {
        //you can place any other error handling code here
        throw new PageNotFoundException("page or resource");
    }

Now, in my Action, I am throwing a Custom Exception that I have created. And my Controller is inheriting from a custom Controller Based class that I have created. The Custom Base Controller was created to override error handling. Here is my custom Base Controller class:

public class MyBasePageController : Controller
{
    protected override void OnException(ExceptionContext filterContext)
    {
        filterContext.GetType();
        filterContext.ExceptionHandled = true;
        this.View("ErrorManager", filterContext).ExecuteResult(this.ControllerContext);
        base.OnException(filterContext);
    }
}

The "ErrorManager" in the above code is just a view that is using a Model based on ExceptionContext

My solution works perfectly and I am able to handle ANY error on my website and display different messages based on ANY exception type.

How do I get the different parts of a Flask request's url?

You can examine the url through several Request fields:

Imagine your application is listening on the following application root:

http://www.example.com/myapplication

And a user requests the following URI:

http://www.example.com/myapplication/foo/page.html?x=y

In this case the values of the above mentioned attributes would be the following:

    path             /foo/page.html
    full_path        /foo/page.html?x=y
    script_root      /myapplication
    base_url         http://www.example.com/myapplication/foo/page.html
    url              http://www.example.com/myapplication/foo/page.html?x=y
    url_root         http://www.example.com/myapplication/

You can easily extract the host part with the appropriate splits.

Fetch frame count with ffmpeg

linux

ffmpeg -i "/home/iorigins/????????????/123.mov" -f null /dev/null

ruby

result = `ffmpeg -i #{path} -f null - 2>&1`
r = result.match("frame=([0-9]+)")
p r[1]

"The given path's format is not supported."

Try changing:

Server.MapPath("/UploadBucket/Raw/")

to

Server.MapPath(@"\UploadBucket\Raw\")

'import' and 'export' may only appear at the top level

I had the same issue using webpack4, i was missing the file .babelrc in the root folder:

{
    "presets":["env", "react"],
    "plugins": [
        "syntax-dynamic-import"
    ]
}

From package.json :

"babel-core": "^6.26.3",
"babel-loader": "^7.1.5",
"babel-plugin-syntax-dynamic-import": "^6.18.0",
"babel-polyfill": "^6.26.0",
"babel-preset-env": "^1.7.0",
"babel-preset-react": "^6.24.1",

jQuery: If this HREF contains

$("a").each(function() {
    if (this.href.indexOf('?') != -1) {
        alert("Contains questionmark");
    }
});

ASP.NET Core Web API Authentication

Now, after I was pointed in the right direction, here's my complete solution:

This is the middleware class which is executed on every incoming request and checks if the request has the correct credentials. If no credentials are present or if they are wrong, the service responds with a 401 Unauthorized error immediately.

public class AuthenticationMiddleware
{
    private readonly RequestDelegate _next;

    public AuthenticationMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        string authHeader = context.Request.Headers["Authorization"];
        if (authHeader != null && authHeader.StartsWith("Basic"))
        {
            //Extract credentials
            string encodedUsernamePassword = authHeader.Substring("Basic ".Length).Trim();
            Encoding encoding = Encoding.GetEncoding("iso-8859-1");
            string usernamePassword = encoding.GetString(Convert.FromBase64String(encodedUsernamePassword));

            int seperatorIndex = usernamePassword.IndexOf(':');

            var username = usernamePassword.Substring(0, seperatorIndex);
            var password = usernamePassword.Substring(seperatorIndex + 1);

            if(username == "test" && password == "test" )
            {
                await _next.Invoke(context);
            }
            else
            {
                context.Response.StatusCode = 401; //Unauthorized
                return;
            }
        }
        else
        {
            // no authorization header
            context.Response.StatusCode = 401; //Unauthorized
            return;
        }
    }
}

The middleware extension needs to be called in the Configure method of the service Startup class

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();

    app.UseMiddleware<AuthenticationMiddleware>();

    app.UseMvc();
}

And that's all! :)

A very good resource for middleware in .Net Core and authentication can be found here: https://www.exceptionnotfound.net/writing-custom-middleware-in-asp-net-core-1-0/

Show popup after page load

You can also do this much easier with a plugin called jQuery-confirm. All you have to do is add the script tag and the style sheet they provide in your page

<link rel="stylesheet" 
href="https://cdnjs.cloudflare.com/ajax/libs/jquery-
confirm/3.3.0/jquery-confirm.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery-
confirm/3.3.0/jquery-confirm.min.js"></script>

And then an example of calling the alert box is:

   <script>
        $.alert({
    title: 'Alert!',
    content: 'Simple alert!',
     });

lexical or preprocessor issue file not found occurs while archiving?

In my case I was developing a framework and had a test application inside it, what was missing is inside the test application target -> build settings -> Framework Search Paths:

  • The value needed to be the framework path (the build output - .framework) which is in my case: "../FrameworkNameFolder/" - the 2 points indicates to go one folder up.

Also, inside the test application target -> Build Phases -> Link Binary With Libraries:

  • I had to remove the framework file, clean the project, add the framework file again, compile and this also solved the issue.

How do I upload a file to an SFTP server in C# (.NET)?

Unfortunately, it's not in the .NET Framework itself. My wish is that you could integrate with FileZilla, but I don't think it exposes an interface. They do have scripting I think, but it won't be as clean obviously.

I've used CuteFTP in a project which does SFTP. It exposes a COM component which I created a .NET wrapper around. The catch, you'll find, is permissions. It runs beautifully under the Windows credentials which installed CuteFTP, but running under other credentials requires permissions to be set in DCOM.

How to Allow Remote Access to PostgreSQL database

If using PostgreSql 9.5.1, please follow the below configuration:

  1. Open hg_hba.conf in pgAdmin pgAdmin
  2. Select your path, and open it, then add a setting pg_hba.conf
  3. Restart postgresql service

How to Count Duplicates in List with LINQ

You can also do Dictionary:

 var list = new List<string> { "a", "b", "a", "c", "a", "b" };
 var result = list.GroupBy(x => x)
            .ToDictionary(y=>y.Key, y=>y.Count())
            .OrderByDescending(z => z.Value);

 foreach (var x in result)
        {
            Console.WriteLine("Value: " + x.Key + " Count: " + x.Value);
        }

Pushing from local repository to GitHub hosted remote

Subversion implicitly has the remote repository associated with it at all times. Git, on the other hand, allows many "remotes", each of which represents a single remote place you can push to or pull from.

You need to add a remote for the GitHub repository to your local repository, then use git push ${remote} or git pull ${remote} to push and pull respectively - or the GUI equivalents.

Pro Git discusses remotes here: http://git-scm.com/book/ch2-5.html

The GitHub help also discusses them in a more "task-focused" way here: http://help.github.com/remotes/

Once you have associated the two you will be able to push or pull branches.

Adding values to specific DataTable cells

You mean you want to add a new row and only put data in a certain column? Try the following:

var row = dataTable.NewRow();
row[myColumn].Value = "my new value";
dataTable.Add(row);

As it is a data table, though, there will always be data of some kind in every column. It just might be DBNull.Value instead of whatever data type you imagine it would be.

Hash Map in Python

In python you would use a dictionary.

It is a very important type in python and often used.

You can create one easily by

name = {}

Dictionaries have many methods:

# add entries:
>>> name['first'] = 'John'
>>> name['second'] = 'Doe'
>>> name
{'first': 'John', 'second': 'Doe'}

# you can store all objects and datatypes as value in a dictionary
# as key you can use all objects and datatypes that are hashable
>>> name['list'] = ['list', 'inside', 'dict']
>>> name[1] = 1
>>> name
{'first': 'John', 'second': 'Doe', 1: 1, 'list': ['list', 'inside', 'dict']}

You can not influence the order of a dict.

Concatenate multiple result rows of one column into one, group by another column

You can use array_agg function for that:

SELECT "Movie",
array_to_string(array_agg(distinct "Actor"),',') AS Actor
FROM Table1
GROUP BY "Movie";

Result:

MOVIE ACTOR
A 1,2,3
B 4

See this SQLFiddle

For more See 9.18. Aggregate Functions

Jenkins could not run git

It seems Jenkins has been changing a lot. I fixed this problem in March 2017 by doing this:

  1. Go to Manage Jenkins
  2. Go to Global Tool Configuration
  3. In Git / Path to Git executable enter C:\<whatever the path is>\git.exe.
  4. Click on Save.

Best way to check if a Data Table has a null value in it

DataTable dt = new DataTable();
foreach (DataRow dr in dt.Rows)
{
    if (dr["Column_Name"] == DBNull.Value)
    {
        //Do something
    }
    else
    {
        //Do something
    }
}

Java: how to use UrlConnection to post request with authorization?

I don't see anywhere in the code where you specify that this is a POST request. Then again, you need a java.net.HttpURLConnection to do that.

In fact, I highly recommend using HttpURLConnection instead of URLConnection, with conn.setRequestMethod("POST"); and see if it still gives you problems.

How can I remount my Android/system as read-write in a bash script using adb?

Probable cause that remount fails is you are not running adb as root.

Shell Script should be as follow.

# Script to mount Android Device as read/write.
# List the Devices.
adb devices;

# Run adb as root (Needs root access).
adb root;

# Since you're running as root su is not required
adb shell mount -o rw,remount /;

If this fails, you could try the below:

# List the Devices.
adb devices;

# Run adb as root
adb root;

adb remount;
adb shell su -c "mount -o rw,remount /";

To find which user you are:

$ adb shell whoami

Error:attempt to apply non-function

You're missing *s in the last two terms of your expression, so R is interpreting (e.g.) 0.207 (log(DIAM93))^2 as an attempt to call a function named 0.207 ...

For example:

> 1 + 2*(3)
[1] 7
> 1 + 2 (3)

Error: attempt to apply non-function

Your (unreproducible) expression should read:

censusdata_20$AGB93 = WD * exp(-1.239 + 1.980 * log (DIAM93) + 
                              0.207* (log(DIAM93))^2  -
                              0.0281*(log(DIAM93))^3)

Mathematica is the only computer system I know of that allows juxtaposition to be used for multiplication ...

Android Studio Checkout Github Error "CreateProcess=2" (Windows)

If you have downloaded Github Desktop Client 1.0.9 then the path for git.exe will be

C:\Users\Username\AppData\Local\GitHubDesktop\app-1.0.9\resources\app\git\cmd\git.exe

How to convert a hex string to hex number

Try this:

hex_str = "0xAD4"
hex_int = int(hex_str, 16)
new_int = hex_int + 0x200
print hex(new_int)

If you don't like the 0x in the beginning, replace the last line with

print hex(new_int)[2:]

How do I access named capturing groups in a .NET Regex?

This answers improves on Rashmi Pandit's answer, which is in a way better than the rest because that it seems to completely resolve the exact problem detailed in the question.

The bad part is that is inefficient and not uses the IgnoreCase option consistently.

Inefficient part is because regex can be expensive to construct and execute, and in that answer it could have been constructed just once (calling Regex.IsMatch was just constructing the regex again behind the scene). And Match method could have been called only once and stored in a variable and then linkand name should call Result from that variable.

And the IgnoreCase option was only used in the Match part but not in the Regex.IsMatch part.

I also moved the Regex definition outside the method in order to construct it just once (I think is the sensible approach if we are storing that the assembly with the RegexOptions.Compiled option).

private static Regex hrefRegex = new Regex("<td>\\s*<a\\s*href\\s*=\\s*(?:\"(?<link>[^\"]*)\"|(?<link>\\S+))\\s*>(?<name>.*)\\s*</a>\\s*</td>",  RegexOptions.IgnoreCase | RegexOptions.Compiled);

public static bool TryGetHrefDetails(string htmlTd, out string link, out string name)
{
    var matches = hrefRegex.Match(htmlTd);
    if (matches.Success)
    {
        link = matches.Result("${link}");
        name = matches.Result("${name}");
        return true;
    }
    else
    {
        link = null;
        name = null;
        return false;
    }
}

How to calculate the IP range when the IP address and the netmask is given?

I learned this shortcut from working at the network deployment position. It helped me so much, I figured I will share this secret with everyone. So far, I have not able to find an easier way online that I know of.

For example a network 192.115.103.64 /27, what is the range?

just remember that subnet mask is 0, 128, 192, 224, 240, 248, 252, 254, 255

255.255.255.255 11111111.11111111.11111111.11111111 /32

255.255.255.254 11111111.11111111.11111111.11111110 /31

255.255.255.252 11111111.11111111.11111111.11111100 /30

255.255.255.248 11111111.11111111.11111111.11111000 /29

255.255.255.240 11111111.11111111.11111111.11110000 /28

255.255.255.224 11111111.11111111.11111111.11100000 /27

255.255.255.192 11111111.11111111.11111111.11000000 /26

255.255.255.128 11111111.11111111.11111111.10000000 /25

255.255.255.0 11111111.11111111.11111111.00000000 /24

from /27 we know that (11111111.11111111.11111111.11100000). Counting from the left, it is the third number from the last octet, which equal 255.255.255.224 subnet mask. (Don't count 0, 0 is /24) so 128, 192, 224..etc

Here where the math comes in:

use the subnet mask - subnet mask of the previous listed subnet mask in this case 224-192=32

We know 192.115.103.64 is the network: 64 + 32 = 96 (the next network for /27)

which means we have .0 .32. 64. 96. 128. 160. 192. 224. (Can't use 256 because it is .255)

Here is the range 64 -- 96.

network is 64.

first host is 65.(first network +1)

Last host is 94. (broadcast -1)

broadcast is 95. (last network -1)

Convert cells(1,1) into "A1" and vice versa

The Address property of a cell can get this for you:

MsgBox Cells(1, 1).Address(RowAbsolute:=False, ColumnAbsolute:=False)

returns A1.

The other way around can be done with the Row and Column property of Range:

MsgBox Range("A1").Row & ", " & Range("A1").Column

returns 1,1.

Add day(s) to a Date object

date.setTime( date.getTime() + days * 86400000 );

Android Fragment onClick button Method

Your activity must have

public void insertIntoDb(View v) {
...
} 

not Fragment .

If you don't want the above in activity. initialize button in fragment and set listener to the same.

<Button
    android:id="@+id/btn_conferma" // + missing

Then

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

   View view = inflater.inflate(R.layout.fragment_rssitem_detail,
    container, false);
   Button button = (Button) view.findViewById(R.id.btn_conferma);
   button.setOnClickListener(new OnClickListener()
   {
             @Override
             public void onClick(View v)
             {
                // do something
             } 
   }); 
   return view;
}

MVVM Passing EventArgs As Command Parameter

I try to keep my dependencies to a minimum, so I implemented this myself instead of going with EventToCommand of MVVMLight. Works for me so far, but feedback is welcome.

Xaml:

<i:Interaction.Behaviors>
    <beh:EventToCommandBehavior Command="{Binding DropCommand}" Event="Drop" PassArguments="True" />
</i:Interaction.Behaviors>

ViewModel:

public ActionCommand<DragEventArgs> DropCommand { get; private set; }

this.DropCommand = new ActionCommand<DragEventArgs>(OnDrop);

private void OnDrop(DragEventArgs e)
{
    // ...
}

EventToCommandBehavior:

/// <summary>
/// Behavior that will connect an UI event to a viewmodel Command,
/// allowing the event arguments to be passed as the CommandParameter.
/// </summary>
public class EventToCommandBehavior : Behavior<FrameworkElement>
{
    private Delegate _handler;
    private EventInfo _oldEvent;

    // Event
    public string Event { get { return (string)GetValue(EventProperty); } set { SetValue(EventProperty, value); } }
    public static readonly DependencyProperty EventProperty = DependencyProperty.Register("Event", typeof(string), typeof(EventToCommandBehavior), new PropertyMetadata(null, OnEventChanged));

    // Command
    public ICommand Command { get { return (ICommand)GetValue(CommandProperty); } set { SetValue(CommandProperty, value); } }
    public static readonly DependencyProperty CommandProperty = DependencyProperty.Register("Command", typeof(ICommand), typeof(EventToCommandBehavior), new PropertyMetadata(null));

    // PassArguments (default: false)
    public bool PassArguments { get { return (bool)GetValue(PassArgumentsProperty); } set { SetValue(PassArgumentsProperty, value); } }
    public static readonly DependencyProperty PassArgumentsProperty = DependencyProperty.Register("PassArguments", typeof(bool), typeof(EventToCommandBehavior), new PropertyMetadata(false));


    private static void OnEventChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var beh = (EventToCommandBehavior)d;

        if (beh.AssociatedObject != null) // is not yet attached at initial load
            beh.AttachHandler((string)e.NewValue);
    }

    protected override void OnAttached()
    {
        AttachHandler(this.Event); // initial set
    }

    /// <summary>
    /// Attaches the handler to the event
    /// </summary>
    private void AttachHandler(string eventName)
    {
        // detach old event
        if (_oldEvent != null)
            _oldEvent.RemoveEventHandler(this.AssociatedObject, _handler);

        // attach new event
        if (!string.IsNullOrEmpty(eventName))
        {
            EventInfo ei = this.AssociatedObject.GetType().GetEvent(eventName);
            if (ei != null)
            {
                MethodInfo mi = this.GetType().GetMethod("ExecuteCommand", BindingFlags.Instance | BindingFlags.NonPublic);
                _handler = Delegate.CreateDelegate(ei.EventHandlerType, this, mi);
                ei.AddEventHandler(this.AssociatedObject, _handler);
                _oldEvent = ei; // store to detach in case the Event property changes
            }
            else
                throw new ArgumentException(string.Format("The event '{0}' was not found on type '{1}'", eventName, this.AssociatedObject.GetType().Name));
        }
    }

    /// <summary>
    /// Executes the Command
    /// </summary>
    private void ExecuteCommand(object sender, EventArgs e)
    {
        object parameter = this.PassArguments ? e : null;
        if (this.Command != null)
        {
            if (this.Command.CanExecute(parameter))
                this.Command.Execute(parameter);
        }
    }
}

ActionCommand:

public class ActionCommand<T> : ICommand
{
    public event EventHandler CanExecuteChanged;
    private Action<T> _action;

    public ActionCommand(Action<T> action)
    {
        _action = action;
    }

    public bool CanExecute(object parameter) { return true; }

    public void Execute(object parameter)
    {
        if (_action != null)
        {
            var castParameter = (T)Convert.ChangeType(parameter, typeof(T));
            _action(castParameter);
        }
    }
}

How to copy data from one HDFS to another HDFS?

distcp command use for copying from one cluster to another cluster in parallel. You have to set the path for namenode of src and path for namenode of dst, internally it use mapper.

Example:

$ hadoop distcp <src> <dst>

there few options you can set for distcp

-m for no. of mapper for copying data this will increase speed of copying.

-atomic for auto commit the data.

-update will only update data that is in old version.

There are generic command for copying files in hadoop are -cp and -put but they are use only when the data volume is less.

Node Version Manager (NVM) on Windows

The first thing that we need to do is install NVM.

  1. Uninstall existing version of node since we won’t be using it anymore
  2. Delete any existing nodejs installation directories. e.g. “C:\Program Files\nodejs”) that might remain. NVM’s generated symlink will not overwrite an existing (even empty) installation directory.
  3. Delete the npm install directory at C:\Users[Your User]\AppData\Roaming\npm We are now ready to install nvm. Download the installer from https://github.com/coreybutler/nvm/releases

To upgrade, run the new installer. It will safely overwrite the files it needs to update without touching your node.js installations. Make sure you use the same installation and symlink folder. If you originally installed to the default locations, you just need to click “next” on each window until it finishes.

Credits Directly copied from : https://digitaldrummerj.me/windows-running-multiple-versions-of-node/

How to convert index of a pandas dataframe into a column?

either:

df['index1'] = df.index

or, .reset_index:

df.reset_index(level=0, inplace=True)

so, if you have a multi-index frame with 3 levels of index, like:

>>> df
                       val
tick       tag obs        
2016-02-26 C   2    0.0139
2016-02-27 A   2    0.5577
2016-02-28 C   6    0.0303

and you want to convert the 1st (tick) and 3rd (obs) levels in the index into columns, you would do:

>>> df.reset_index(level=['tick', 'obs'])
          tick  obs     val
tag                        
C   2016-02-26    2  0.0139
A   2016-02-27    2  0.5577
C   2016-02-28    6  0.0303

maven-dependency-plugin (goals "copy-dependencies", "unpack") is not supported by m2e

If copy-dependencies, unpack, pack, etc., are important for your project you shouldn't ignore it. You have to enclose your <plugins> in <pluginManagement> tested with Eclipse Indigo SR1, maven 2.2.1

How to move from one fragment to another fragment on click of an ImageView in Android?

Add this code where you want to click and load Fragment. I hope it's work for you.


Fragment fragment = new yourfragment();
        FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fragment_container, fragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();

Difference between a Structure and a Union

As you already state in your question, the main difference between union and struct is that union members overlay the memory of each other so that the sizeof of a union is the one , while struct members are laid out one after each other (with optional padding in between). Also an union is large enough to contain all its members, and have an alignment that fits all its members. So let's say int can only be stored at 2 byte addresses and is 2 bytes wide, and long can only be stored at 4 byte addresses and is 4 bytes long. The following union

union test {
    int a;
    long b;
}; 

could have a sizeof of 4, and an alignment requirement of 4. Both an union and a struct can have padding at the end, but not at their beginning. Writing to a struct changes only the value of the member written to. Writing to a member of an union will render the value of all other members invalid. You cannot access them if you haven't written to them before, otherwise the behavior is undefined. GCC provides as an extension that you can actually read from members of an union, even though you haven't written to them most recently. For an Operation System, it doesn't have to matter whether a user program writes to an union or to a structure. This actually is only an issue of the compiler.

Another important property of union and struct is, they allow that a pointer to them can point to types of any of its members. So the following is valid:

struct test {
    int a;
    double b;
} * some_test_pointer;

some_test_pointer can point to int* or double*. If you cast an address of type test to int*, it will point to its first member, a, actually. The same is true for an union too. Thus, because an union will always have the right alignment, you can use an union to make pointing to some type valid:

union a {
    int a;
    double b;
};

That union will actually be able to point to an int, and a double:

union a * v = (union a*)some_int_pointer;
*some_int_pointer = 5;
v->a = 10;
return *some_int_pointer;    

is actually valid, as stated by the C99 standard:

An object shall have its stored value accessed only by an lvalue expression that has one of the following types:

  • a type compatible with the effective type of the object
  • ...
  • an aggregate or union type that includes one of the aforementioned types among its members

The compiler won't optimize out the v->a = 10; as it could affect the value of *some_int_pointer (and the function will return 10 instead of 5).

How to retrieve the dimensions of a view?

You can use a broadcast that is called in OnResume ()

For example:

int vh = 0;   
int vw = 0;

public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.maindemo);  //<- includes the grid called "board"

      registerReceiver(new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                TableLayout tl = (TableLayout) findViewById(R.id.board);  
                tl = (TableLayout) findViewById(R.id.board);
                vh = tl.getHeight();       
                vw = tl.getWidth();               
            }
      }, new IntentFilter("Test"));
}

protected void onResume() {
        super.onResume();

        Intent it = new Intent("Test");
        sendBroadcast(it);

}

You can not get the height of a view in OnCreate (), onStart (), or even in onResume () for the reason that kcoppock responded

Fastest way to update 120 Million records

If your int_field is indexed, remove the index before running the update. Then create your index again...

5 hours seem like a lot for 120 million recs.

Bootstrap 3 - 100% height of custom div inside column

I was just looking for a smiliar issue and I found this:

.div{
  height : 100vh;
}

more info

vw: 1/100th viewport width
vh: 1/100th viewport height
vmin: 1/100th of the smallest side
vmax: 1/100th of the largest side

What is the difference between '/' and '//' when used for division?

>>> print 5.0 / 2
2.5

>>> print 5.0 // 2
2.0

How to install SignTool.exe for Windows 10

I did a modify with the Visual Studio from Control Panel, Programs and Features. The SDK was not at first apparent so I installed the Common Tools which lo and behold did include the SDK Update 3.

How to remove .html from URL?

Good question, but it seems to have confused people. The answers are almost equally divided between those who thought Dave (the OP) was saving his HTML pages without the .html extension, and those who thought he was saving them as normal (with .html), but wanting the URL to show up without. While the question could have been worded a little better, I think it’s clear what he meant. If he was saving pages without .html, his two question (‘how to remove .html') and (how to ‘redirect any url with .html’) would be exactly the same question! So that interpretation doesn’t make much sense. Also, his first comment (about avoiding an infinite loop) and his own answer seem to confirm this.

So let’s start by rephrasing the question and breaking down the task. We want to accomplish two things:

  1. Visibly remove the .html if it’s part of the requested URL (e.g. /page.html)
  2. Point the cropped URL (e.g. /page) back to the actual file (/page.html).

There’s nothing difficult about doing either of these things. (We could achieve the second one simply by enabling MultiViews.) The challenge here is doing them both without creating an infinite loop.

Dave’s own answer got the job done, but it’s pretty convoluted and not at all portable. (Sorry Dave.) Lukasz Habrzyk seems to have cleaned up Anmol’s answer, and finally Amit Verma improved on them both. However, none of them explained how their solutions solved the fundamental problem—how to avoid an infinite loop. As I understand it, they work because THE_REQUEST variable holds the original request from the browser. As such, the condition (RewriteCond %{THE_REQUEST}) only gets triggered once. Since it doesn’t get triggered upon a rewrite, you avoid the infinite loop scenario. But then you're dealing with the full HTTP request—GET, HTTP and all—which partly explains some of the uglier regex examples on this page.

I’m going to offer one more approach, which I think is easier to understand. I hope this helps future readers understand the code they’re using, rather than just copying and pasting code they barely understand and hoping for the best.

RewriteEngine on

# Remove .html (or htm) from visible URL (permanent redirect)
RewriteCond %{REQUEST_URI} ^/(.+)\.html?$ [nocase]
RewriteRule ^ /%1 [L,R=301]

# Quietly point back to the HTML file (temporary/undefined redirect):
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}.html -f
RewriteRule ^ %{REQUEST_URI}.html [END]

Let’s break it down…

The first rule is pretty simple. The condition matches any URL ending in .html (or .htm) and redirects to the URL without the filename extension. It's a permanent redirect to indicate that the cropped URL is the canonical one.

The second rule is simple too. The first condition will only pass if the requested filename is not a valid directory (!-d). The second will only pass if the filename refers to a valid file (-f) with the .html extension added. If both conditions pass, the rewrite rule simply adds ‘.html’ to the filename. And then the magic happens… [END]. Yep, that’s all it takes to prevent an infinite loop. The Apache RewriteRule Flags documentation explains it:

Using the [END] flag terminates not only the current round of rewrite processing (like [L]) but also prevents any subsequent rewrite processing from occurring in per-directory (htaccess) context.

jQuery: Selecting by class and input type

Just in case any dummies like me tried the suggestions here with a button and found nothing worked, you probably want this:

$(':button.myclass')

Could not open a connection to your authentication agent

Note: this is an answer to this question, which has been merged with this one. That question was for Windows 7, meaning my answer was for Cygwin/MSYS/MSYS2. This one seems for some unix, where I wouldn't expect the SSH agent needing to be managed like this.

This will run the SSH agent and authenticate only the first time you need it, not every time you open your Bash terminal. It can be used for any program using SSH in general, including ssh itself and scp. Just add this to /etc/profile.d/ssh-helper.sh:

ssh-auth() {
    # Start the SSH agent only if not running
    [[ -z $(ps | grep ssh-agent) ]] && echo $(ssh-agent) > /tmp/ssh-agent-data.sh

    # Identify the running SSH agent
    [[ -z $SSH_AGENT_PID ]] && source /tmp/ssh-agent-data.sh > /dev/null

    # Authenticate (change key path or make a symlink if needed)
    [[ -z $(ssh-add -l | grep "/home/$(whoami)/.ssh/id_rsa") ]] && ssh-add
}

# You can repeat this for other commands using SSH
git() { ssh-auth; command git "$@"; }

Django: multiple models in one template using forms

I currently have a workaround functional (it passes my unit tests). It is a good solution to my opinion when you only want to add a limited number of fields from other models.

Am I missing something here ?

class UserProfileForm(ModelForm):
    def __init__(self, instance=None, *args, **kwargs):
        # Add these fields from the user object
        _fields = ('first_name', 'last_name', 'email',)
        # Retrieve initial (current) data from the user object
        _initial = model_to_dict(instance.user, _fields) if instance is not None else {}
        # Pass the initial data to the base
        super(UserProfileForm, self).__init__(initial=_initial, instance=instance, *args, **kwargs)
        # Retrieve the fields from the user model and update the fields with it
        self.fields.update(fields_for_model(User, _fields))

    class Meta:
        model = UserProfile
        exclude = ('user',)

    def save(self, *args, **kwargs):
        u = self.instance.user
        u.first_name = self.cleaned_data['first_name']
        u.last_name = self.cleaned_data['last_name']
        u.email = self.cleaned_data['email']
        u.save()
        profile = super(UserProfileForm, self).save(*args,**kwargs)
        return profile

I can't understand why this JAXB IllegalAnnotationException is thrown

I can't understand why this JAXB IllegalAnnotationException is thrown

I also was getting the ### counts of IllegalAnnotationExceptions exception and it seemed to be due to an improper dependency hierarchy in my Spring wiring.

I figured it out by putting a breakpoint in the JAXB code when it does the throw. For me this was at com.sun.xml.bind.v2.runtime.IllegalAnnotationsException$Builder.check(). Then I dumped the list variable which gives something like:

[org.mortbay.jetty.Handler is an interface, and JAXB can't handle interfaces.
this problem is related to the following location:
    at org.mortbay.jetty.Handler
    at public org.mortbay.jetty.Handler[] org.mortbay.jetty.handler.HandlerCollection.getHandlers()
    at org.mortbay.jetty.handler.HandlerCollection
    at org.mortbay.jetty.handler.ContextHandlerCollection
    at com.mprew.ec2.commons.server.LocalContextHandlerCollection
    at private com.mprew.ec2.commons.server.LocalContextHandlerCollection com.mprew.ec2.commons.services.jaxws_asm.SetLocalContextHandlerCollection.arg0
    at com.mprew.ec2.commons.services.jaxws_asm.SetLocalContextHandlerCollection,
org.mortbay.jetty.Handler does not have a no-arg default constructor.]
....

The does not have a no-arg default constructor seemed to me to be misleading. Maybe I wasn't understanding what the exception was saying. But it did indicate that there was a problem with my LocalContextHandlerCollection. I removed a dependency loop and the error cleared.

Hopefully this will be helpful to others.

How to get method parameter names?

In python 3, below is to make *args and **kwargs into a dict (use OrderedDict for python < 3.6 to maintain dict orders):

from functools import wraps

def display_param(func):
    @wraps(func)
    def wrapper(*args, **kwargs):

        param = inspect.signature(func).parameters
        all_param = {
            k: args[n] if n < len(args) else v.default
            for n, (k, v) in enumerate(param.items()) if k != 'kwargs'
        }
        all_param .update(kwargs)
        print(all_param)

        return func(**all_param)
    return wrapper

Spring Boot - Loading Initial Data

I created a library that facilitates initial/demo data loading in a Spring Boot application. You can find it at https://github.com/piotrpolak/spring-boot-data-fixtures

Once the data fixtures starter is on the classpath, it will automatically try to load DICTIONARY data upon application startup (this behavior can be controlled by properties) - all you need to do is to register a bean implementing DataFixture.

I find loading initial data by code superior to loading it using SQL scripts:

  • the logic of your fixtures lives close to your application logic/domain model and it is subject to refactoring as your domain evolves
  • you benefit from incremental demo data updates - imagine a QA environment with some user data (that needs not to be lost after application deploy) but at the same time you want to add data for the new features you developed

Example data fixture:

/**
 * You can have as many fixture classes as you want.
 * @Order annotation is respected for the fixtures belonging to the same set.
 * You can make your demo database to be incrementally updated with fresh data
 * each time the application is redeployed - all you need to do is to write
 * a good condition in `canBeLoaded()` method.
 */
@Component
public class InitialDataFixture implements DataFixture {

    private final LanguageRepository languageRepository;

    // ...

    @Override
    public DataFixtureSet getSet() {
      return DataFixtureSet.DICTIONARY;
    }

    /**
     * We want to make sure the fixture is applied once and once only.
     * A more sophisticated condition can be used to create incremental demo data
     * over time without the need to reset the QA database (for example).
     */
    @Override
    public boolean canBeLoaded() {
      return languageRepository.size() == 0;
    }

    /**
     * The actual application of the fixture.
     * Assuming that data fixtures are registered as beans, this method can call
     * other services and/or repositories.
     */
    @Override
    public void load() {
      languageRepository.saveAll(Arrays.asList(
          new Language("en-US"), new Language("pl-PL")));
    }
}

The concept is inspired by the Symfony Doctrine Data Fixtures bundle.

How to import cv2 in python3?

Make a virtual enviroment using python3

virtualenv env_name --python="python3"

and run the following command

pip3 install opencv-python

Running an executable in Mac Terminal

Unix will only run commands if they are available on the system path, as you can view by the $PATH variable

echo $PATH

Executables located in directories that are not on the path cannot be run unless you specify their full location. So in your case, assuming the executable is in the current directory you are working with, then you can execute it as such

./my-exec

Where my-exec is the name of your program.

How to view DB2 Table structure

Generally it's easiest to use DESCRIBE.

DESCRIBE TABLE MYSCHEMA.TABLE

or

DESCRIBE INDEXES FOR MYSCHEMA.TABLE SHOW DETAIL

etc.

See the documentation: DESCRIBE command

String formatting in Python 3

Here are the docs about the "new" format syntax. An example would be:

"({:d} goals, ${:d})".format(self.goals, self.penalties)

If both goals and penalties are integers (i.e. their default format is ok), it could be shortened to:

"({} goals, ${})".format(self.goals, self.penalties)

And since the parameters are fields of self, there's also a way of doing it using a single argument twice (as @Burhan Khalid noted in the comments):

"({0.goals} goals, ${0.penalties})".format(self)

Explaining:

  • {} means just the next positional argument, with default format;
  • {0} means the argument with index 0, with default format;
  • {:d} is the next positional argument, with decimal integer format;
  • {0:d} is the argument with index 0, with decimal integer format.

There are many others things you can do when selecting an argument (using named arguments instead of positional ones, accessing fields, etc) and many format options as well (padding the number, using thousands separators, showing sign or not, etc). Some other examples:

"({goals} goals, ${penalties})".format(goals=2, penalties=4)
"({goals} goals, ${penalties})".format(**self.__dict__)

"first goal: {0.goal_list[0]}".format(self)
"second goal: {.goal_list[1]}".format(self)

"conversion rate: {:.2f}".format(self.goals / self.shots) # '0.20'
"conversion rate: {:.2%}".format(self.goals / self.shots) # '20.45%'
"conversion rate: {:.0%}".format(self.goals / self.shots) # '20%'

"self: {!s}".format(self) # 'Player: Bob'
"self: {!r}".format(self) # '<__main__.Player instance at 0x00BF7260>'

"games: {:>3}".format(player1.games)  # 'games: 123'
"games: {:>3}".format(player2.games)  # 'games:   4'
"games: {:0>3}".format(player2.games) # 'games: 004'

Note: As others pointed out, the new format does not supersede the former, both are available both in Python 3 and the newer versions of Python 2 as well. Some may say it's a matter of preference, but IMHO the newer is much more expressive than the older, and should be used whenever writing new code (unless it's targeting older environments, of course).

Difference between Dictionary and Hashtable

ILookup Interface is used in .net 3.5 with linq.

The HashTable is the base class that is weakly type; the DictionaryBase abstract class is stronly typed and uses internally a HashTable.

I found a a strange thing about Dictionary, when we add the multiple entries in Dictionary, the order in which the entries are added is maintained. Thus if I apply a foreach on the Dictionary, I will get the records in the same order I have inserted them.

Whereas, this is not true with normal HashTable, as when I add same records in Hashtable the order is not maintained. As far as my knowledge goes, Dictionary is based on Hashtable, if this is true, why my Dictionary maintains the order but HashTable does not?

As to why they behave differently, it's because Generic Dictionary implements a hashtable, but is not based on System.Collections.Hashtable. The Generic Dictionary implementation is based on allocating key-value-pairs from a list. These are then indexed with the hashtable buckets for random access, but when it returns an enumerator, it just walks the list in sequential order - which will be the order of insertion as long as entries are not re-used.

shiv govind Birlasoft.:)

How do I execute a Shell built-in command with a C function?

You should execute sh -c echo $PWD; generally sh -c will execute shell commands.

(In fact, system(foo) is defined as execl("sh", "sh", "-c", foo, NULL) and thus works for shell built-ins.)

If you just want the value of PWD, use getenv, though.

Selecting with complex criteria from pandas.DataFrame

Another solution is to use the query method:

import pandas as pd

from random import randint
df = pd.DataFrame({'A': [randint(1, 9) for x in xrange(10)],
                   'B': [randint(1, 9) * 10 for x in xrange(10)],
                   'C': [randint(1, 9) * 100 for x in xrange(10)]})
print df

   A   B    C
0  7  20  300
1  7  80  700
2  4  90  100
3  4  30  900
4  7  80  200
5  7  60  800
6  3  80  900
7  9  40  100
8  6  40  100
9  3  10  600

print df.query('B > 50 and C != 900')

   A   B    C
1  7  80  700
2  4  90  100
4  7  80  200
5  7  60  800

Now if you want to change the returned values in column A you can save their index:

my_query_index = df.query('B > 50 & C != 900').index

....and use .iloc to change them i.e:

df.iloc[my_query_index, 0] = 5000

print df

      A   B    C
0     7  20  300
1  5000  80  700
2  5000  90  100
3     4  30  900
4  5000  80  200
5  5000  60  800
6     3  80  900
7     9  40  100
8     6  40  100
9     3  10  600

Redirect using AngularJS

Check your routing method:

if your routing state is like this

 .state('app.register', {
    url: '/register',
    views: {
      'menuContent': {
        templateUrl: 'templates/register.html',
      }
    }
  }) 

then you should use

$location.path("/app/register");

Label points in geom_point

Instead of using the ifelse as in the above example, one can also prefilter the data prior to labeling based on some threshold values, this saves a lot of work for the plotting device:

xlimit <- 36
ylimit <- 24
ggplot(myData)+geom_point(aes(myX,myY))+
    geom_label(data=myData[myData$myX > xlimit & myData$myY> ylimit,], aes(myX,myY,myLabel))

Get top first record from duplicate records having no unique identity

Doesn't SELECT DISTINCT help? I suppose it would return the result you want.

matching query does not exist Error in Django

In case anybody is here and the other two solutions do not make the trick, check that what you are using to filter is what you expect:

user = UniversityDetails.objects.get(email=email)

is email a str, or a None? or an int?

what is difference between success and .done() method of $.ajax

.success() only gets called if your webserver responds with a 200 OK HTTP header - basically when everything is fine.

The callbacks attached to done() will be fired when the deferred is resolved. The callbacks attached to fail() will be fired when the deferred is rejected.

promise.done(doneCallback).fail(failCallback)

.done() has only one callback and it is the success callback

What does #defining WIN32_LEAN_AND_MEAN exclude exactly?

Complementing the above answers and also "Parroting" from the Windows Dev Center documentation,

The Winsock2.h header file internally includes core elements from the Windows.h header file, so there is not usually an #include line for the Windows.h header file in Winsock applications. If an #include line is needed for the Windows.h header file, this should be preceded with the #define WIN32_LEAN_AND_MEAN macro. For historical reasons, the Windows.h header defaults to including the Winsock.h header file for Windows Sockets 1.1. The declarations in the Winsock.h header file will conflict with the declarations in the Winsock2.h header file required by Windows Sockets 2.0. The WIN32_LEAN_AND_MEAN macro prevents the Winsock.h from being included by the Windows.h header ..

PHP: How to handle <![CDATA[ with SimpleXMLElement?

This did the trick for me:

echo trim($entry->title);

How can I set / change DNS using the command-prompt at windows 8

Now you can change the primary dns (index=1), assuming that your interface is static (not using dhcp)

You can set your DNS servers statically even if you use DHCP to obtain your IP address.

Example under Windows 7 to add two DN servers, the command is as follows:

netsh interface ipv4 add dns "Local Area Connection" address=192.168.x.x index=1 netsh interface ipv4 add dns "Local Area Connection" address=192.168.x.x index=2

How to count the number of columns in a table using SQL?

Maybe something like this:

SELECT count(*) FROM user_tab_columns WHERE table_name = 'FOO'

this will count number of columns in a the table FOO

You can also just

select count(*) from all_tab_columns where owner='BAR' and table_name='FOO';

where the owner is schema and note that Table Names are upper case

jquery's append not working with svg element?

Found an easy way which works with all browsers I have (Chrome 49, Edge 25, Firefox 44, IE11, Safari 5 [Win], Safari 8 (MacOS)) :

_x000D_
_x000D_
// Clean svg content (if you want to update the svg's objects)_x000D_
// Note : .html('') doesn't works for svg in some browsers_x000D_
$('#svgObject').empty();_x000D_
// add some objects_x000D_
$('#svgObject').append('<polygon class="svgStyle" points="10,10 50,10 50,50 10,50 10,10" />');_x000D_
$('#svgObject').append('<circle class="svgStyle" cx="100" cy="30" r="25"/>');_x000D_
_x000D_
// Magic happens here: refresh DOM (you must refresh svg's parent for Edge/IE and Safari)_x000D_
$('#svgContainer').html($('#svgContainer').html());
_x000D_
.svgStyle_x000D_
{_x000D_
  fill:cornflowerblue;_x000D_
  fill-opacity:0.2;_x000D_
  stroke-width:2;_x000D_
  stroke-dasharray:5,5;_x000D_
  stroke:black;_x000D_
}
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
_x000D_
<div id="svgContainer">_x000D_
  <svg id="svgObject" height="100" width="200"></svg>_x000D_
</div>_x000D_
_x000D_
<span>It works if two shapes (one square and one circle) are displayed above.</span>
_x000D_
_x000D_
_x000D_

Assignment inside lambda expression in Python

TL;DR: When using functional idioms it's better to write functional code

As many people have pointed out, in Python lambdas assignment is not allowed. In general when using functional idioms your better off thinking in a functional manner which means wherever possible no side effects and no assignments.

Here is functional solution which uses a lambda. I've assigned the lambda to fn for clarity (and because it got a little long-ish).

from operator import add
from itertools import ifilter, ifilterfalse
fn = lambda l, pred: add(list(ifilter(pred, iter(l))), [ifilterfalse(pred, iter(l)).next()])
objs = [Object(name=""), Object(name="fake_name"), Object(name="")]
fn(objs, lambda o: o.name != '')

You can also make this deal with iterators rather than lists by changing things around a little. You also have some different imports.

from itertools import chain, islice, ifilter, ifilterfalse
fn = lambda l, pred: chain(ifilter(pred, iter(l)), islice(ifilterfalse(pred, iter(l)), 1))

You can always reoganize the code to reduce the length of the statements.

JavaScript or jQuery browser back button click detector

In my case I am using jQuery .load() to update DIVs in a SPA (single page [web] app) .

Being new to working with $(window).on('hashchange', ..) event listener , this one proved challenging and took a bit to hack on. Thanks to reading a lot of answers and trying different variations, finally figured out how to make it work in the following manner. Far as I can tell, it is looking stable so far.

In summary - there is the variable globalCurrentHash that should be set each time you load a view.

Then when $(window).on('hashchange', ..) event listener runs, it checks the following:

  • If location.hash has the same value, it means Going Forward
  • If location.hash has different value, it means Going Back

I realize using global vars isn't the most elegant solution, but doing things OO in JS seems tricky to me so far. Suggestions for improvement/refinement certainly appreciated


Set Up:

  1. Define a global var :
    var globalCurrentHash = null;
  1. When calling .load() to update the DIV, update the global var as well :

    function loadMenuSelection(hrefVal) {
      $('#layout_main').load(nextView);
      globalCurrentHash = hrefVal;
    }
    
  2. On page ready, set up the listener to check the global var to see if Back Button is being pressed:

    $(document).ready(function(){
      $(window).on('hashchange', function(){
          console.log( 'location.hash: ' + location.hash );
          console.log( 'globalCurrentHash: ' + globalCurrentHash );
    
          if (location.hash == globalCurrentHash) {
              console.log( 'Going fwd' );
          }
          else {
    
              console.log( 'Going Back' );
              loadMenuSelection(location.hash);
          }
        });
    
    });
    

Get dates from a week number in T-SQL

DECLARE @dayval int,
 @monthval int,
 @yearval int

SET @dayval = 1
SET @monthval = 1
SET @yearval = 2011


DECLARE @dtDateSerial datetime

        SET @dtDateSerial = DATEADD(day, @dayval-1,
                                DATEADD(month, @monthval-1,
                                    DATEADD(year, @yearval-1900, 0)
                                )
                            )

DECLARE @weekno int
SET @weekno = 53


DECLARE @weekstart datetime
SET @weekstart = dateadd(day, 7 * (@weekno -1) - datepart (dw, @dtDateSerial), @dtDateSerial)

DECLARE @weekend datetime
SET @weekend = dateadd(day, 6, @weekstart)

SELECT @weekstart, @weekend

django templates: include and extends

When you use the extends template tag, you're saying that the current template extends another -- that it is a child template, dependent on a parent template. Django will look at your child template and use its content to populate the parent.

Everything that you want to use in a child template should be within blocks, which Django uses to populate the parent. If you want use an include statement in that child template, you have to put it within a block, for Django to make sense of it. Otherwise it just doesn't make sense and Django doesn't know what to do with it.

The Django documentation has a few really good examples of using blocks to replace blocks in the parent template.

https://docs.djangoproject.com/en/dev/ref/templates/language/#template-inheritance

How do I test which class an object is in Objective-C?

To test if object is an instance of class a:

[yourObject isKindOfClass:[a class]]
// Returns a Boolean value that indicates whether the receiver is an instance of 
// given class or an instance of any class that inherits from that class.

or

[yourObject isMemberOfClass:[a class]]
// Returns a Boolean value that indicates whether the receiver is an instance of a 
// given class.

To get object's class name you can use NSStringFromClass function:

NSString *className = NSStringFromClass([yourObject class]);

or c-function from objective-c runtime api:

#import <objc/runtime.h>

/* ... */

const char* className = class_getName([yourObject class]);
NSLog(@"yourObject is a: %s", className);

EDIT: In Swift

if touch.view is UIPickerView {
    // touch.view is of type UIPickerView
}

How to use Visual Studio C++ Compiler?

You may be forgetting something. Before #include <iostream>, write #include <stdafx.h> and maybe that will help. Then, when you are done writing, click test, than click output from build, then when it is done processing/compiling, press Ctrl+F5 to open the Command Prompt and it should have the output and "press any key to continue."

Error message: (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.)

You should enable the Server authentication mode to mixed mode as following: In SQL Studio, select YourServer -> Property -> Security -> Select SqlServer and Window Authentication mode.

How to get response using cURL in PHP

The crux of the solution is setting

CURLOPT_RETURNTRANSFER => true

then

$response = curl_exec($ch);

CURLOPT_RETURNTRANSFER tells PHP to store the response in a variable instead of printing it to the page, so $response will contain your response. Here's your most basic working code (I think, didn't test it):

// init curl object        
$ch = curl_init();

// define options
$optArray = array(
    CURLOPT_URL => 'http://www.google.com',
    CURLOPT_RETURNTRANSFER => true
);

// apply those options
curl_setopt_array($ch, $optArray);

// execute request and get response
$result = curl_exec($ch);

How do I look inside a Python object?

Try ppretty

from ppretty import ppretty


class A(object):
    s = 5

    def __init__(self):
        self._p = 8

    @property
    def foo(self):
        return range(10)


print ppretty(A(), indent='    ', depth=2, width=30, seq_length=6,
              show_protected=True, show_private=False, show_static=True,
              show_properties=True, show_address=True)

Output:

__main__.A at 0x1debd68L (
    _p = 8, 
    foo = [0, 1, 2, ..., 7, 8, 9], 
    s = 5
)

Need to get a string after a "word" in a string in c#

string originalSting = "This is my string";
string texttobesearched = "my";
string dataAfterTextTobeSearch= finalCommand.Split(new string[] { texttobesearched     }, StringSplitOptions.None).Last();
if(dataAfterTextobeSearch!=originalSting)
{
    //your action here if data is found
}
else
{
    //action if the data being searched was not found
}

Indirectly referenced from required .class file

This issue happen because of few jars are getting references from other jar and reference jar is missing .

Example : Spring framework

Description Resource    Path    Location    Type
The project was not built since its build path is incomplete. Cannot find the class file for org.springframework.beans.factory.annotation.Autowire. Fix the build path then try building this project   SpringBatch     Unknown Java Problem

In this case "org.springframework.beans.factory.annotation.Autowire" is missing.

Spring-bean.jar is missing

Once you add dependency in your class path issue will resolve.

Good examples of python-memcache (memcached) being used in Python?

A good rule of thumb: use the built-in help system in Python. Example below...

jdoe@server:~$ python
Python 2.7.3 (default, Aug  1 2012, 05:14:39) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import memcache
>>> dir()
['__builtins__', '__doc__', '__name__', '__package__', 'memcache']
>>> help(memcache)

------------------------------------------
NAME
    memcache - client module for memcached (memory cache daemon)

FILE
    /usr/lib/python2.7/dist-packages/memcache.py

MODULE DOCS
    http://docs.python.org/library/memcache

DESCRIPTION
    Overview
    ========

    See U{the MemCached homepage<http://www.danga.com/memcached>} for more about memcached.

    Usage summary
    =============
...
------------------------------------------

Parse query string into an array

There are several possible methods, but for you, there is already a builtin parse_str function

$array = array();
parse_str($string, $array);
var_dump($array);

How do I install Java on Mac OSX allowing version switching?

Manually switching system-default version without 3rd party tools:

As detailed in this older answer, on macOS /usr/bin/java is a wrapper tool that will use Java version pointed by JAVA_HOME or if that variable is not set will look for Java installations under /Library/Java/JavaVirtualMachines/ and will use the one with highest version. It determines versions by looking at Contents/Info.plist under each package.

Armed with this knowledge you can:

  • control which version the system will use by renaming Info.plist in versions you don't want to use as default (that file is not used by the actual Java runtime itself).
  • control which version to use for specific tasks by setting $JAVA_HOME

I've just verified this is still true with OpenJDK & Mojave.

On a brand new system, there is no Java version installed:

$ java -version
No Java runtime present, requesting install.

Cancel this, download OpenJDK 11 & 12ea on https://jdk.java.net ; install OpenJDK11:

$ cd /Library/Java/JavaVirtualMachines/
$ sudo tar xzf ~/Downloads/openjdk-11.0.1_osx-x64_bin.tar.gz

System java is now 11:

$ java -version
openjdk version "11.0.1" 2018-10-16
[...]

Install OpenJDK12 (early access at the moment):

$ sudo tar xzf ~/Downloads/openjdk-12-ea+17_osx-x64_bin.tar.gz 

System java is now 12:

$ java -version
openjdk version "12-ea" 2019-03-19
[...]

Now let's "hide" OpenJDK 12 from system java wrapper:

$ cd jdk-12.jdk/Contents/
$ sudo mv Info.plist Info.plist.disabled

System java is back to 11:

$ java -version
openjdk version "11.0.1" 2018-10-16
[...]

And you can still use version 12 punctually by manually setting JAVA_HOME:

$ export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk-12.jdk/Contents/Home
$ java -version
openjdk version "12-ea" 2019-03-19
[...]

How to update-alternatives to Python 3 without breaking apt?

Somehow python 3 came back (after some updates?) and is causing big issues with apt updates, so I've decided to remove python 3 completely from the alternatives:

root:~# python -V
Python 3.5.2

root:~# update-alternatives --config python
There are 2 choices for the alternative python (providing /usr/bin/python).

  Selection    Path                Priority   Status
------------------------------------------------------------
* 0            /usr/bin/python3.5   3         auto mode
  1            /usr/bin/python2.7   2         manual mode
  2            /usr/bin/python3.5   3         manual mode


root:~# update-alternatives --remove python /usr/bin/python3.5

root:~# update-alternatives --config python
There is 1 choice for the alternative python (providing /usr/bin/python).

    Selection    Path                Priority   Status
------------------------------------------------------------
  0            /usr/bin/python2.7   2         auto mode
* 1            /usr/bin/python2.7   2         manual mode

Press <enter> to keep the current choice[*], or type selection number: 0


root:~# python -V
Python 2.7.12

root:~# update-alternatives --config python
There is only one alternative in link group python (providing /usr/bin/python): /usr/bin/python2.7
Nothing to configure.

Getting ORA-01031: insufficient privileges while querying a table instead of ORA-00942: table or view does not exist

In SQL Developer: Everything was working fine and I had all the permissions to login and there was no password change and I could click the table and see the data tab.

But when I run query (simple select statement) it was showing "ORA-01031: insufficient privileges" message.

The solution is simply disconnect the connection and reconnect. Note: only doing Reconnect did not work for me. SQL Developer Disconnect Snapshot

System.Net.WebException: The remote name could not be resolved:

Open the hosts file located at : **C:\windows\system32\drivers\etc**.

Hosts file is for what?

Add the following at end of this file :

YourServerIP YourDNS

Example:

198.168.1.1 maps.google.com

Parse XML using JavaScript

I'm guessing from your last question, asked 20 minutes before this one, that you are trying to parse (read and convert) the XML found through using GeoNames' FindNearestAddress.

If your XML is in a string variable called txt and looks like this:

<address>
  <street>Roble Ave</street>
  <mtfcc>S1400</mtfcc>
  <streetNumber>649</streetNumber>
  <lat>37.45127</lat>
  <lng>-122.18032</lng>
  <distance>0.04</distance>
  <postalcode>94025</postalcode>
  <placename>Menlo Park</placename>
  <adminCode2>081</adminCode2>
  <adminName2>San Mateo</adminName2>
  <adminCode1>CA</adminCode1>
  <adminName1>California</adminName1>
  <countryCode>US</countryCode>
</address>

Then you can parse the XML with Javascript DOM like this:

if (window.DOMParser)
{
    parser = new DOMParser();
    xmlDoc = parser.parseFromString(txt, "text/xml");
}
else // Internet Explorer
{
    xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
    xmlDoc.async = false;
    xmlDoc.loadXML(txt);
}

And get specific values from the nodes like this:

//Gets house address number
xmlDoc.getElementsByTagName("streetNumber")[0].childNodes[0].nodeValue;

//Gets Street name
xmlDoc.getElementsByTagName("street")[0].childNodes[0].nodeValue;

//Gets Postal Code
xmlDoc.getElementsByTagName("postalcode")[0].childNodes[0].nodeValue;

JSFiddle


Feb. 2019 edit:

In response to @gaugeinvariante's concerns about xml with Namespace prefixes. Should you have a need to parse xml with Namespace prefixes, everything should work almost identically:

NOTE: this will only work in browsers that support xml namespace prefixes such as Microsoft Edge

_x000D_
_x000D_
// XML with namespace prefixes 's', 'sn', and 'p' in a variable called txt_x000D_
txt = `_x000D_
<address xmlns:p='example.com/postal' xmlns:s='example.com/street' xmlns:sn='example.com/streetNum'>_x000D_
  <s:street>Roble Ave</s:street>_x000D_
  <sn:streetNumber>649</sn:streetNumber>_x000D_
  <p:postalcode>94025</p:postalcode>_x000D_
</address>`;_x000D_
_x000D_
//Everything else the same_x000D_
if (window.DOMParser)_x000D_
{_x000D_
    parser = new DOMParser();_x000D_
    xmlDoc = parser.parseFromString(txt, "text/xml");_x000D_
}_x000D_
else // Internet Explorer_x000D_
{_x000D_
    xmlDoc = new ActiveXObject("Microsoft.XMLDOM");_x000D_
    xmlDoc.async = false;_x000D_
    xmlDoc.loadXML(txt);_x000D_
}_x000D_
_x000D_
//The prefix should not be included when you request the xml namespace_x000D_
//Gets "streetNumber" (note there is no prefix of "sn"_x000D_
console.log(xmlDoc.getElementsByTagName("streetNumber")[0].childNodes[0].nodeValue);_x000D_
_x000D_
//Gets Street name_x000D_
console.log(xmlDoc.getElementsByTagName("street")[0].childNodes[0].nodeValue);_x000D_
_x000D_
//Gets Postal Code_x000D_
console.log(xmlDoc.getElementsByTagName("postalcode")[0].childNodes[0].nodeValue);
_x000D_
_x000D_
_x000D_

Cannot issue data manipulation statements with executeQuery()

If you're using spring boot, just add an @Modifying annotation.

@Modifying
@Query
(value = "UPDATE user SET middleName = 'Mudd' WHERE id = 1", nativeQuery = true)
void updateMiddleName();

Can a foreign key refer to a primary key in the same table?

A good example of using ids of other rows in the same table as foreign keys is nested lists.

Deleting a row that has children (i.e., rows, which refer to parent's id), which also have children (i.e., referencing ids of children) will delete a cascade of rows.

This will save a lot of pain (and a lot of code of what to do with orphans - i.e., rows, that refer to non-existing ids).

how get yesterday and tomorrow datetime in c#

Use DateTime.AddDays() (MSDN Documentation DateTime.AddDays Method).

DateTime tomorrow = DateTime.Now.AddDays(1);
DateTime yesterday = DateTime.Now.AddDays(-1);

How to execute a bash command stored as a string with quotes and asterisk

You don't need the "eval" even. Just put a dollar sign in front of the string:

cmd="ls"
$cmd

Git merge reports "Already up-to-date" though there is a difference

git merge origin/master instead git merge master worked for me. So to merge master into feature branch you may use:

git checkout feature_branch
git merge origin/master

How to change the author and committer name and e-mail of multiple commits in Git?

Your problem is really common. See "Using Mailmap to Fix Authors List in Git"

For the sake of simplicity, I have created a script to ease the process: git-changemail

After putting that script on your path, you can issue commands like:

  • Change author matchings on current branch

    $ git changemail -a [email protected] -n newname -m [email protected]
    
  • Change author and committer matchings on <branch> and <branch4>. Pass -f to filter-branch to allow rewriting backups

    $ git changemail -b [email protected] -n newname -m [email protected] -- -f &lt;branch> &lt;branch2>
    
  • Show existing users on repo

    $ git changemail --show-both
    

By the way, after making your changes, clean the backup from the filter-branch with: git-backup-clean

How to access site running apache server over lan without internet connection

I was trying to access my localhost website (on my pc) from my mobile (andriod). The configuration is like Windows 10, WAMP 2.4.23, PHP Website and my mobile was running on andriod. Both my mobile and pc are connected to same wifi.

I was able to open my website on my pc by using url http://localhost/mysite or http://127.0.0.1/mysite. My pc ip was 192.168.0.1 (say) and my mobile ip was 192.168.0.2 (say) and both connected on same wifi.

I tried all the setting like changing the httpd.conf, httpd-vhosts.conf only to find that all I need was to disable my firewall. Of course, disabling the firewall completely is not a good idea. I have avast antivirus running on my pc. If I check the firewall log for last one hour (or so) I can see that attempt has been made by my mobile ip to connect to website running on my pc. All it required was to add an exception by creating a new rule in avast UI which will allow connections from my mobile ip.

Hope this helps someone.

Change a column type from Date to DateTime during ROR migration

Also, if you're using Rails 3 or newer you don't have to use the up and down methods. You can just use change:

class ChangeFormatInMyTable < ActiveRecord::Migration
  def change
    change_column :my_table, :my_column, :my_new_type
  end
end

Powershell Get-ChildItem most recent file in directory

If you want the latest file in the directory and you are using only the LastWriteTime to determine the latest file, you can do something like below:

gci path | sort LastWriteTime | select -last 1

On the other hand, if you want to only rely on the names that have the dates in them, you should be able to something similar

gci path | select -last 1

Also, if there are directories in the directory, you might want to add a ?{-not $_.PsIsContainer}

Javascript - remove an array item by value

function removeValue(arr, value) {
    for(var i = 0; i < arr.length; i++) {
        if(arr[i] === value) {
            arr.splice(i, 1);
            break;
        }
    }
    return arr;
}

This can be called like so:

removeValue(tag_story, 90);

Flutter - Layout a Grid

There are few named constructors in GridView for different scenarios,

Constructors

  1. GridView
  2. GridView.builder
  3. GridView.count
  4. GridView.custom
  5. GridView.extent

Below is a example of GridView constructor:

import 'package:flutter/material.dart';

void main() => runApp(
  MaterialApp(
    home: ExampleGrid(),
  ),
);

class ExampleGrid extends StatelessWidget {
  List<String> images = [
    "https://uae.microless.com/cdn/no_image.jpg",
    "https://images-na.ssl-images-amazon.com/images/I/81aF3Ob-2KL._UX679_.jpg",
    "https://www.boostmobile.com/content/dam/boostmobile/en/products/phones/apple/iphone-7/silver/device-front.png.transform/pdpCarousel/image.jpg",
    "https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSgUgs8_kmuhScsx-J01d8fA1mhlCR5-1jyvMYxqCB8h3LCqcgl9Q",
    "https://ae01.alicdn.com/kf/HTB11tA5aiAKL1JjSZFoq6ygCFXaw/Unlocked-Samsung-GALAXY-S2-I9100-Mobile-Phone-Android-Wi-Fi-GPS-8-0MP-camera-Core-4.jpg_640x640.jpg",
    "https://media.ed.edmunds-media.com/gmc/sierra-3500hd/2018/td/2018_gmc_sierra-3500hd_f34_td_411183_1600.jpg",
    "https://hips.hearstapps.com/amv-prod-cad-assets.s3.amazonaws.com/images/16q1/665019/2016-chevrolet-silverado-2500hd-high-country-diesel-test-review-car-and-driver-photo-665520-s-original.jpg",
    "https://www.galeanasvandykedodge.net/assets/stock/ColorMatched_01/White/640/cc_2018DOV170002_01_640/cc_2018DOV170002_01_640_PSC.jpg",
    "https://media.onthemarket.com/properties/6191869/797156548/composite.jpg",
    "https://media.onthemarket.com/properties/6191840/797152761/composite.jpg",
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: GridView(
        physics: BouncingScrollPhysics(), // if you want IOS bouncing effect, otherwise remove this line
        gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),//change the number as you want
        children: images.map((url) {
          return Card(child: Image.network(url));
        }).toList(),
      ),
    );
  }
}

If you want your GridView items to be dynamic according to the content, you can few lines to do that but the simplest way to use StaggeredGridView package. I have provided an answer with example here.

Below is an example for a GridView.count:

import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: ExampleGrid(),
      ),
    );

class ExampleGrid extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: GridView.count(
        crossAxisCount: 4,
        children: List.generate(40, (index) {
          return Card(
            child: Image.network("https://robohash.org/$index"),
          ); //robohash.org api provide you different images for any number you are giving
        }),
      ),
    );
  }
}

Screenshot for above snippet:

Flutter gridview example by blasanka using card widget and robohash api

Example for a SliverGridView:

import 'package:flutter/material.dart';

void main() => runApp(
      MaterialApp(
        home: ExampleGrid(),
      ),
    );

class ExampleGrid extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        primary: false,
        slivers: <Widget>[
          SliverPadding(
            padding: const EdgeInsets.all(20.0),
            sliver: SliverGrid.count(
              crossAxisSpacing: 10.0,
              crossAxisCount: 2,
              children: List.generate(20, (index) {
                return Card(child: Image.network("https://robohash.org/$index"));
              }),
            ),
          ),
        ],
      )
    );
  }
}

YouTube API to fetch all videos on a channel

Here is a video from Google Developers showing how to list all videos in a channel in v3 of the YouTube API.

There are two steps:

  1. Query Channels to get the "uploads" Id. eg https://www.googleapis.com/youtube/v3/channels?id={channel Id}&key={API key}&part=contentDetails

  2. Use this "uploads" Id to query PlaylistItems to get the list of videos. eg https://www.googleapis.com/youtube/v3/playlistItems?playlistId={"uploads" Id}&key={API key}&part=snippet&maxResults=50

How can I get the current stack trace in Java?

I have a utility method that returns a string with the stacktrace:

static String getStackTrace(Throwable t) {
    StringWriter sw = new StringWriter();
    PrintWriter pw = new PrintWriter(sw, true);
    t.printStackTrace(pw);
    pw.flush();
    sw.flush();
    return sw.toString();
}

And just logit like...

... 
catch (FileNotFoundException e) {
    logger.config(getStackTrace(e));
}

In Go's http package, how do I get the query string on a POST request?

There are two ways of getting query params:

  1. Using reqeust.URL.Query()
  2. Using request.Form

In second case one has to be careful as body parameters will take precedence over query parameters. A full description about getting query params can be found here

https://golangbyexample.com/net-http-package-get-query-params-golang

How do you set your pythonpath in an already-created virtualenv?

It's already answered here -> Is my virtual environment (python) causing my PYTHONPATH to break?

UNIX/LINUX

Add "export PYTHONPATH=/usr/local/lib/python2.0" this to ~/.bashrc file and source it by typing "source ~/.bashrc" OR ". ~/.bashrc".

WINDOWS XP

1) Go to the Control panel 2) Double click System 3) Go to the Advanced tab 4) Click on Environment Variables

In the System Variables window, check if you have a variable named PYTHONPATH. If you have one already, check that it points to the right directories. If you don't have one already, click the New button and create it.

PYTHON CODE

Alternatively, you can also do below your code:-

import sys
sys.path.append("/home/me/mypy") 

What is the Record type in typescript?

  1. Can someone give a simple definition of what Record is?

A Record<K, T> is an object type whose property keys are K and whose property values are T. That is, keyof Record<K, T> is equivalent to K, and Record<K, T>[K] is (basically) equivalent to T.

  1. Is Record<K,T> merely a way of saying "all properties on this object will have type T"? Probably not all objects, since K has some purpose...

As you note, K has a purpose... to limit the property keys to particular values. If you want to accept all possible string-valued keys, you could do something like Record<string, T>, but the idiomatic way of doing that is to use an index signature like { [k: string]: T }.

  1. Does the K generic forbid additional keys on the object that are not K, or does it allow them and just indicate that their properties are not transformed to T?

It doesn't exactly "forbid" additional keys: after all, a value is generally allowed to have properties not explicitly mentioned in its type... but it wouldn't recognize that such properties exist:

declare const x: Record<"a", string>;
x.b; // error, Property 'b' does not exist on type 'Record<"a", string>'

and it would treat them as excess properties which are sometimes rejected:

declare function acceptR(x: Record<"a", string>): void;
acceptR({a: "hey", b: "you"}); // error, Object literal may only specify known properties

and sometimes accepted:

const y = {a: "hey", b: "you"};
acceptR(y); // okay
  1. With the given example:

    type ThreeStringProps = Record<'prop1' | 'prop2' | 'prop3', string>
    

    Is it exactly the same as this?:

    type ThreeStringProps = {prop1: string, prop2: string, prop3: string}
    

Yes!

Hope that helps. Good luck!

Get day of week in SQL Server 2005/2008

EUROPE:

declare @d datetime;
set @d=getdate();
set @dow=((datepart(dw,@d) + @@DATEFIRST-2) % 7+1);

How should the ViewModel close the form?

I would go this way:

using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.Command;    
using GalaSoft.MvvmLight.Messaging; 

// View

public partial class TestCloseWindow : Window
{
    public TestCloseWindow() {
        InitializeComponent();
        Messenger.Default.Register<CloseWindowMsg>(this, (msg) => Close());
    }
}

// View Model

public class MainViewModel: ViewModelBase
{
    ICommand _closeChildWindowCommand;

    public ICommand CloseChildWindowCommand {
        get {
            return _closeChildWindowCommand?? (_closeChildWindowCommand = new RelayCommand(() => {
                Messenger.Default.Send(new CloseWindowMsg());
        }));
        }
    }
}

public class CloseWindowMsg
{
}

Split a large pandas dataframe

I guess now we can use plain iloc with range for this.

chunk_size = int(df.shape[0] / 4)
for start in range(0, df.shape[0], chunk_size):
    df_subset = df.iloc[start:start + chunk_size]
    process_data(df_subset)
    ....

"static const" vs "#define" vs "enum"

Another drawback of const in C is that you can't use the value in initializing another const.

static int const NUMBER_OF_FINGERS_PER_HAND = 5;
static int const NUMBER_OF_HANDS = 2;

// initializer element is not constant, this does not work.
static int const NUMBER_OF_FINGERS = NUMBER_OF_FINGERS_PER_HAND 
                                     * NUMBER_OF_HANDS;

Even this does not work with a const since the compiler does not see it as a constant:

static uint8_t const ARRAY_SIZE = 16;
static int8_t const lookup_table[ARRAY_SIZE] = {
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}; // ARRAY_SIZE not a constant!

I'd be happy to use typed const in these cases, otherwise...

Android Studio Image Asset Launcher Icon Background Color

First, create a launcher icon (Adaptive and Legacy) from Image Asset:

Select an image for background layer and resize it to 0% or 1% and In legacy tab set shape to none.

Then, delete folder res/mipmap/ic_laucher_round in the project window and Open AndroidManifest.xml and remove attribute android:roundIcon="@mipmap/ic_launcher_round" from the application element.

In the end, delete ic_launcher.xml from mipmap-anydpi-v26.

Notice that: Some devices like Nexus 5X (Android 8.1) adding a white background automatically and can't do anything.

CodeIgniter Disallowed Key Characters

To use CodeIgniter with jQuery Ajax, use "Object" as data instead of Query string as below:

$.ajax({
    url: site_url + "ajax/signup",
    data: ({'email': email, 'password': password}), //<--- Use Object
    type: "post",
    success: function(response, textStatus, jqXHR){
        $('#sign-up').html(response);
    },
    error: function(jqXHR, textStatus, errorThrown){
        console.log("The following error occured: "+
                    textStatus, errorThrown);
    }
});

How to send characters in PuTTY serial communication only when pressing enter?

The settings you need are "Local echo" and "Line editing" under the "Terminal" category on the left.

To get the characters to display on the screen as you enter them, set "Local echo" to "Force on".

To get the terminal to not send the command until you press Enter, set "Local line editing" to "Force on".

PuTTY Line discipline options

Explanation:

From the PuTTY User Manual (Found by clicking on the "Help" button in PuTTY):

4.3.8 ‘Local echo’

With local echo disabled, characters you type into the PuTTY window are not echoed in the window by PuTTY. They are simply sent to the server. (The server might choose to echo them back to you; this can't be controlled from the PuTTY control panel.)

Some types of session need local echo, and many do not. In its default mode, PuTTY will automatically attempt to deduce whether or not local echo is appropriate for the session you are working in. If you find it has made the wrong decision, you can use this configuration option to override its choice: you can force local echo to be turned on, or force it to be turned off, instead of relying on the automatic detection.

4.3.9 ‘Local line editing’ Normally, every character you type into the PuTTY window is sent immediately to the server the moment you type it.

If you enable local line editing, this changes. PuTTY will let you edit a whole line at a time locally, and the line will only be sent to the server when you press Return. If you make a mistake, you can use the Backspace key to correct it before you press Return, and the server will never see the mistake.

Since it is hard to edit a line locally without being able to see it, local line editing is mostly used in conjunction with local echo (section 4.3.8). This makes it ideal for use in raw mode or when connecting to MUDs or talkers. (Although some more advanced MUDs do occasionally turn local line editing on and turn local echo off, in order to accept a password from the user.)

Some types of session need local line editing, and many do not. In its default mode, PuTTY will automatically attempt to deduce whether or not local line editing is appropriate for the session you are working in. If you find it has made the wrong decision, you can use this configuration option to override its choice: you can force local line editing to be turned on, or force it to be turned off, instead of relying on the automatic detection.

Putty sometimes makes wrong choices when "Auto" is enabled for these options because it tries to detect the connection configuration. Applied to serial line, this is a bit trickier to do.

Fast query runs slow in SSRS

I will add that I had the same problem with a non-stored procedure query - just a plain select statement. To fix it, I declared a variable within the dataset SQL statement and set it equal to the SSRS parameter.

What an annoying workaround! Still, thank you all for getting me close to the answer!

Confusing error in R: Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings, : line 1 did not have 42 elements)

To read characters try

scan("/PathTo/file.csv", "")

If you're reading numeric values, then just use

scan("/PathTo/file.csv")

scan by default will use white space as separator. The type of the second arg defines 'what' to read (defaults to double()).

Overcoming "Display forbidden by X-Frame-Options"

FWIW:

We had a situation where we needed to kill our iFrame when this "breaker" code showed up. So, I used the PHP function get_headers($url); to check out the remote URL before showing it in an iFrame. For better performance, I cached the results to a file so I was not making a HTTP connection each time.

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

python and sys.argv

I would do it this way:

import sys

def main(argv):
    if len(argv) < 2:
        sys.stderr.write("Usage: %s <database>" % (argv[0],))
        return 1

    if not os.path.exists(argv[1]):
        sys.stderr.write("ERROR: Database %r was not found!" % (argv[1],))
        return 1

if __name__ == "__main__":
    sys.exit(main(sys.argv))

This allows main() to be imported into other modules if desired, and simplifies debugging because you can choose what argv should be.

Get image dimensions

Using getimagesize function, we can also get these properties of that specific image-

<?php

list($width, $height, $type, $attr) = getimagesize("image_name.jpg");

echo "Width: " .$width. "<br />";
echo "Height: " .$height. "<br />";
echo "Type: " .$type. "<br />";
echo "Attribute: " .$attr. "<br />";

//Using array
$arr = array('h' => $height, 'w' => $width, 't' => $type, 'a' => $attr);
?>


Result like this -

Width: 200
Height: 100
Type: 2
Attribute: width='200' height='100'


Type of image consider like -

1 = GIF
2 = JPG
3 = PNG
4 = SWF
5 = PSD
6 = BMP
7 = TIFF(intel byte order)
8 = TIFF(motorola byte order)
9 = JPC
10 = JP2
11 = JPX
12 = JB2
13 = SWC
14 = IFF
15 = WBMP
16 = XBM

How can I check for IsPostBack in JavaScript?

The solution didn't work for me, I had to adapt it:

protected void Page_Load(object sender, EventArgs e)
{
    string script;
    if (IsPostBack)
    {
        script = "var isPostBack = true;";
    }
    else
    {
        script = "var isPostBack = false;";
    }
    Page.ClientScript.RegisterStartupScript(GetType(), "IsPostBack", script, true);
}

Hope this helps.

java.util.Date format SSSSSS: if not microseconds what are the last 3 digits?

From the documentation of SimpleDateFormat:

Letter     Date or Time Component     Presentation     Examples  
S          Millisecond                Number           978 

So it is milliseconds, or 1/1000th of a second. You just format it with on 6 digits, so you add 3 extra leading zeroes...

You can check it this way:

    Date d =new Date();
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSS").format(d));
    System.out.println(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSSSSS").format(d));

Output:

2013-10-07 12:13:27.132
2013-10-07 12:13:27.132
2013-10-07 12:13:27.132
2013-10-07 12:13:27.0132
2013-10-07 12:13:27.00132
2013-10-07 12:13:27.000132

(Ideone fiddle)

A failure occurred while executing com.android.build.gradle.internal.tasks

If any one having this issue in flutter after adding firebase storage. Do flutter clean and re run it, it will work

How to append to New Line in Node.js

It looks like you're running this on Windows (given your H://log.txt file path).

Try using \r\n instead of just \n.

Honestly, \n is fine; you're probably viewing the log file in notepad or something else that doesn't render non-Windows newlines. Try opening it in a different viewer/editor (e.g. Wordpad).

Right way to reverse a pandas DataFrame?

One way to do this if dealing with sorted range index is:

data = data.sort_index(ascending=False)

This approach has the benefits of (1) being a single line, (2) not requiring a utility function, and most importantly (3) not actually changing any of the data in the dataframe.

Caveat: this works by sorting the index in descending order and so may not always be appropriate or generalize for any given Dataframe.

Dropdown using javascript onchange

It does not work because your script in JSFiddle is running inside it's own scope (see the "OnLoad" drop down on the left?).

One way around this is to bind your event handler in javascript (where it should be):

document.getElementById('optionID').onchange = function () {
    document.getElementById("message").innerHTML = "Having a Baby!!";
};

Another way is to modify your code for the fiddle environment and explicitly declare your function as global so it can be found by your inline event handler:

window.changeMessage() {
    document.getElementById("message").innerHTML = "Having a Baby!!";
};

?

PHP + MySQL transactions examples

The idea I generally use when working with transactions looks like this (semi-pseudo-code):

try {
    // First of all, let's begin a transaction
    $db->beginTransaction();
    
    // A set of queries; if one fails, an exception should be thrown
    $db->query('first query');
    $db->query('second query');
    $db->query('third query');
    
    // If we arrive here, it means that no exception was thrown
    // i.e. no query has failed, and we can commit the transaction
    $db->commit();
} catch (\Throwable $e) {
    // An exception has been thrown
    // We must rollback the transaction
    $db->rollback();
    throw $e; // but the error must be handled anyway
}

Note that, with this idea, if a query fails, an Exception must be thrown:
  • PDO can do that, depending on how you configure it
  • else, with some other API, you might have to test the result of the function used to execute a query, and throw an exception yourself.

Unfortunately, there is no magic involved. You cannot just put an instruction somewhere and have transactions done automatically: you still have to specific which group of queries must be executed in a transaction.

For example, quite often you'll have a couple of queries before the transaction (before the begin) and another couple of queries after the transaction (after either commit or rollback) and you'll want those queries executed no matter what happened (or not) in the transaction.

Calculate Age in MySQL (InnoDb)

There is two simples ways to do that :

1-

select("users.birthdate",
            DB::raw("FLOOR(DATEDIFF(CURRENT_DATE, STR_TO_DATE(users.birthdate, '%Y-%m-%d'))/365) AS age_way_one"),

2-

select("users.birthdate",DB::raw("(YEAR(CURDATE())-YEAR(users.birthdate)) AS age_way_two"))

How to list active connections on PostgreSQL?

Oh, I just found that command on PostgreSQL forum:

SELECT * FROM pg_stat_activity;

Selecting a row of pandas series/dataframe by integer index

You can think DataFrame as a dict of Series. df[key] try to select the column index by key and returns a Series object.

However slicing inside of [] slices the rows, because it's a very common operation.

You can read the document for detail:

http://pandas.pydata.org/pandas-docs/stable/indexing.html#basics

AngularJS. How to call controller function from outside of controller component

I use to work with $http, when a want to get some information from a resource I do the following:

angular.module('services.value', [])

.service('Value', function($http, $q) {

var URL = "http://localhost:8080/myWeb/rest/";

var valid = false;

return {
    isValid: valid,
    getIsValid: function(callback){
        return $http.get(URL + email+'/'+password, {cache: false})
                    .success(function(data){
            if(data === 'true'){ valid = true; }
        }).then(callback);
    }}
    });

And the code in the controller:

angular.module('controllers.value', ['services.value'])

.controller('ValueController', function($scope, Value) {
    $scope.obtainValue = function(){
        Value.getIsValid(function(){$scope.printValue();});
    }

    $scope.printValue = function(){
        console.log("Do it, and value is " Value.isValid);
    }
}

I send to the service what function have to call in the controller

How to set Spinner default value to null?

is it possible have a spinner that loads with nothing selected

Only if there is no data. If you have 1+ items in the SpinnerAdapter, the Spinner will always have a selection.

Spinners are not designed to be command widgets. Users will not expect a selection in a Spinner to start an activity. Please consider using something else, like a ListView or GridView, instead of a Spinner.


EDIT

BTW, I forgot to mention -- you can always put an extra entry in your adapter that represents "no selection", and make it the initial selected item in the Spinner.

C# - Making a Process.Start wait until the process has start-up

I also needed this once, and I did a check on the window title of the process. If it is the one you expect, you can be sure the application is running. The application I was checking needed some time for startup and this method worked fine for me.

var process = Process.Start("popup.exe");
while(process.MainWindowTitle != "Title")
{
    Thread.Sleep(10);
}

jQuery - If element has class do this

First, you're missing some parentheses in your conditional:

if ($("#about").hasClass("opened")) {
  $("#about").animate({right: "-700px"}, 2000);
}

But you can also simplify this to:

$('#about.opened').animate(...);

If #about doesn't have the opened class, it won't animate.

If the problem is with the animation itself, we'd need to know more about your element positioning (absolute? absolute inside relative parent? does the parent have layout?)

Spring MVC How take the parameter value of a GET HTTP Request in my controller method?

As explained in the documentation, by using an @RequestParam annotation:

public @ResponseBody String byParameter(@RequestParam("foo") String foo) {
    return "Mapped by path + method + presence of query parameter! (MappingController) - foo = "
           + foo;
}

A TypeScript GUID class?

I found this https://typescriptbcl.codeplex.com/SourceControl/latest

here is the Guid version they have in case the link does not work later.

module System {
    export class Guid {
        constructor (public guid: string) {
            this._guid = guid;
        }

        private _guid: string;

        public ToString(): string {
            return this.guid;
        }

        // Static member
        static MakeNew(): Guid {
            var result: string;
            var i: string;
            var j: number;

            result = "";
            for (j = 0; j < 32; j++) {
                if (j == 8 || j == 12 || j == 16 || j == 20)
                    result = result + '-';
                i = Math.floor(Math.random() * 16).toString(16).toUpperCase();
                result = result + i;
            }
            return new Guid(result);
        }
    }
}

How can I use a C++ library from node.js?

You can use a node.js extension to provide bindings for your C++ code. Here is one tutorial that covers that:

http://syskall.com/how-to-write-your-own-native-nodejs-extension

How to count how many values per level in a given factor?

In case I just want to know how many unique factor levels exist in the data, I use:

length(unique(df$factorcolumn))

How to call an element in a numpy array?

TL;DR:

Using slicing:

>>> import numpy as np
>>> 
>>> arr = np.array([[1,2,3,4,5],[6,7,8,9,10]])
>>> 
>>> arr[0,0]
1
>>> arr[1,1]
7
>>> arr[1,0]
6
>>> arr[1,-1]
10
>>> arr[1,-2]
9

In Long:

Hopefully this helps in your understanding:

>>> import numpy as np
>>> np.array([ [1,2,3], [4,5,6] ])
array([[1, 2, 3],
       [4, 5, 6]])
>>> x = np.array([ [1,2,3], [4,5,6] ])
>>> x[1][2] # 2nd row, 3rd column 
6
>>> x[1,2] # Similarly
6

But to appreciate why slicing is useful, in more dimensions:

>>> np.array([ [[1,2,3], [4,5,6]], [[7,8,9],[10,11,12]] ])
array([[[ 1,  2,  3],
        [ 4,  5,  6]],

       [[ 7,  8,  9],
        [10, 11, 12]]])
>>> x = np.array([ [[1,2,3], [4,5,6]], [[7,8,9],[10,11,12]] ])

>>> x[1][0][2] # 2nd matrix, 1st row, 3rd column
9
>>> x[1,0,2] # Similarly
9

>>> x[1][0:2][2] # 2nd matrix, 1st row, 3rd column
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: index 2 is out of bounds for axis 0 with size 2

>>> x[1, 0:2, 2] # 2nd matrix, 1st and 2nd row, 3rd column
array([ 9, 12])

>>> x[1, 0:2, 1:3] # 2nd matrix, 1st and 2nd row, 2nd and 3rd column
array([[ 8,  9],
       [11, 12]])

Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

Difference between each annotation are :

+-------------------------------------------------------------------------------------------------------+
¦                                       Feature                            ¦   Junit 4    ¦   Junit 5   ¦
¦--------------------------------------------------------------------------+--------------+-------------¦
¦ Execute before all test methods of the class are executed.               ¦ @BeforeClass ¦ @BeforeAll  ¦
¦ Used with static method.                                                 ¦              ¦             ¦
¦ For example, This method could contain some initialization code          ¦              ¦             ¦
¦-------------------------------------------------------------------------------------------------------¦
¦ Execute after all test methods in the current class.                     ¦ @AfterClass  ¦ @AfterAll   ¦
¦ Used with static method.                                                 ¦              ¦             ¦
¦ For example, This method could contain some cleanup code.                ¦              ¦             ¦
¦-------------------------------------------------------------------------------------------------------¦
¦ Execute before each test method.                                         ¦ @Before      ¦ @BeforeEach ¦
¦ Used with non-static method.                                             ¦              ¦             ¦
¦ For example, to reinitialize some class attributes used by the methods.  ¦              ¦             ¦
¦-------------------------------------------------------------------------------------------------------¦
¦ Execute after each test method.                                          ¦ @After       ¦ @AfterEach  ¦
¦ Used with non-static method.                                             ¦              ¦             ¦
¦ For example, to roll back database modifications.                        ¦              ¦             ¦
+-------------------------------------------------------------------------------------------------------+

Most of annotations in both versions are same, but few differs.

Reference

Order of Execution.

Dashed box -> optional annotation.

enter image description here

How to print the number of characters in each line of a text file

Here is example using xargs:

$ xargs -d '\n' -I% sh -c 'echo % | wc -c' < file

How to directly execute SQL query in C#?

IMPORTANT NOTE: You should not concatenate SQL queries unless you trust the user completely. Query concatenation involves risk of SQL Injection being used to take over the world, ...khem, your database.

If you don't want to go into details how to execute query using SqlCommand then you could call the same command line like this:

string userInput = "Brian";
var process = new Process();
var startInfo = new ProcessStartInfo();
startInfo.WindowStyle = ProcessWindowStyle.Hidden;
startInfo.FileName = "cmd.exe";
startInfo.Arguments = string.Format(@"sqlcmd.exe -S .\PDATA_SQLEXPRESS -U sa -P 2BeChanged! -d PDATA_SQLEXPRESS  
     -s ; -W -w 100 -Q "" SELECT tPatCulIntPatIDPk, tPatSFirstname, tPatSName,
     tPatDBirthday  FROM  [dbo].[TPatientRaw] WHERE tPatSName = '{0}' """, userInput);

process.StartInfo = startInfo;
process.Start();

Just ensure that you escape each double quote " with ""

React - How to force a function component to render?

Update react v16.8 (16 Feb 2019 realease)

Since react 16.8 released with hooks, function components are now have the ability to hold persistent state. With that ability you can now mimic a forceUpdate:

_x000D_
_x000D_
function App() {_x000D_
  const [, updateState] = React.useState();_x000D_
  const forceUpdate = React.useCallback(() => updateState({}), []);_x000D_
  console.log("render");_x000D_
  return (_x000D_
    <div>_x000D_
      <button onClick={forceUpdate}>Force Render</button>_x000D_
    </div>_x000D_
  );_x000D_
}_x000D_
_x000D_
const rootElement = document.getElementById("root");_x000D_
ReactDOM.render(<App />, rootElement);
_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.8.1/umd/react.production.min.js"></script>_x000D_
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.8.1/umd/react-dom.production.min.js"></script>_x000D_
<div id="root"/>
_x000D_
_x000D_
_x000D_

Note that this approach should be re-considered and in most cases when you need to force an update you probably doing something wrong.


Before react 16.8.0

No you can't, State-Less function components are just normal functions that returns jsx, you don't have any access to the React life cycle methods as you are not extending from the React.Component.

Think of function-component as the render method part of the class components.

How to convert a pymongo.cursor.Cursor into a dict?

The find method returns a Cursor instance, which allows you to iterate over all matching documents.

To get the first document that matches the given criteria you need to use find_one. The result of find_one is a dictionary.

You can always use the list constructor to return a list of all the documents in the collection but bear in mind that this will load all the data in memory and may not be what you want.

You should do that if you need to reuse the cursor and have a good reason not to use rewind()


Demo using find:

>>> import pymongo
>>> conn = pymongo.MongoClient()
>>> db = conn.test #test is my database
>>> col = db.spam #Here spam is my collection
>>> cur = col.find()  
>>> cur
<pymongo.cursor.Cursor object at 0xb6d447ec>
>>> for doc in cur:
...     print(doc)  # or do something with the document
... 
{'a': 1, '_id': ObjectId('54ff30faadd8f30feb90268f'), 'b': 2}
{'a': 1, 'c': 3, '_id': ObjectId('54ff32a2add8f30feb902690'), 'b': 2}

Demo using find_one:

>>> col.find_one()
{'a': 1, '_id': ObjectId('54ff30faadd8f30feb90268f'), 'b': 2}

Log4j2 configuration - No log4j2 configuration file found

Eclipse will never see a file until you force a refresh of the IDE. Its a feature! So you can put the file all over the project and Eclipse will ignore it completely and throw these errors. Hit refresh in Eclipse project view and then it works.

Differences between "BEGIN RSA PRIVATE KEY" and "BEGIN PRIVATE KEY"

See https://polarssl.org/kb/cryptography/asn1-key-structures-in-der-and-pem (search the page for "BEGIN RSA PRIVATE KEY") (archive link for posterity, just in case).

BEGIN RSA PRIVATE KEY is PKCS#1 and is just an RSA key. It is essentially just the key object from PKCS#8, but without the version or algorithm identifier in front. BEGIN PRIVATE KEY is PKCS#8 and indicates that the key type is included in the key data itself. From the link:

The unencrypted PKCS#8 encoded data starts and ends with the tags:

-----BEGIN PRIVATE KEY-----
BASE64 ENCODED DATA
-----END PRIVATE KEY-----

Within the base64 encoded data the following DER structure is present:

PrivateKeyInfo ::= SEQUENCE {
  version         Version,
  algorithm       AlgorithmIdentifier,
  PrivateKey      BIT STRING
}

AlgorithmIdentifier ::= SEQUENCE {
  algorithm       OBJECT IDENTIFIER,
  parameters      ANY DEFINED BY algorithm OPTIONAL
}

So for an RSA private key, the OID is 1.2.840.113549.1.1.1 and there is a RSAPrivateKey as the PrivateKey key data bitstring.

As opposed to BEGIN RSA PRIVATE KEY, which always specifies an RSA key and therefore doesn't include a key type OID. BEGIN RSA PRIVATE KEY is PKCS#1:

RSA Private Key file (PKCS#1)

The RSA private key PEM file is specific for RSA keys.

It starts and ends with the tags:

-----BEGIN RSA PRIVATE KEY-----
BASE64 ENCODED DATA
-----END RSA PRIVATE KEY-----

Within the base64 encoded data the following DER structure is present:

RSAPrivateKey ::= SEQUENCE {
  version           Version,
  modulus           INTEGER,  -- n
  publicExponent    INTEGER,  -- e
  privateExponent   INTEGER,  -- d
  prime1            INTEGER,  -- p
  prime2            INTEGER,  -- q
  exponent1         INTEGER,  -- d mod (p-1)
  exponent2         INTEGER,  -- d mod (q-1)
  coefficient       INTEGER,  -- (inverse of q) mod p
  otherPrimeInfos   OtherPrimeInfos OPTIONAL
}

Number of regex matches

If you know you will want all the matches, you could use the re.findall function. It will return a list of all the matches. Then you can just do len(result) for the number of matches.

Write to CSV file and export it?

A comment about Will's answer, you might want to replace HttpContext.Current.Response.End(); with HttpContext.Current.ApplicationInstance.CompleteRequest(); The reason is that Response.End() throws a System.Threading.ThreadAbortException. It aborts a thread. If you have an exception logger, it will be littered with ThreadAbortExceptions, which in this case is expected behavior.

Intuitively, sending a CSV file to the browser should not raise an exception.

See here for more Is Response.End() considered harmful?

Set attribute without value

The accepted answer doesn't create a name-only attribute anymore (as of September 2017).

You should use JQuery prop() method to create name-only attributes.

$(body).prop('data-body', true)

Meaning of ${project.basedir} in pom.xml

${project.basedir} is the root directory of your project.

${project.build.directory} is equivalent to ${project.basedir}/target

as it is defined here: https://github.com/apache/maven/blob/trunk/maven-model-builder/src/main/resources/org/apache/maven/model/pom-4.0.0.xml#L53

Change placeholder text

Using jquery you can do this by following code:

<input type="text" id="tbxEmail" name="Email" placeholder="Some Text"/>

$('#tbxEmail').attr('placeholder','Some New Text');

How to install the Sun Java JDK on Ubuntu 10.10 (Maverick Meerkat)?

I am assuming that you need the JDK itself. If so you can accomplish this with:

sudo add-apt-repository ppa:sun-java-community-team/sun-java6

sudo apt-get update

sudo apt-get install sun-java6-jdk

You don't really need to go around editing sources or anything along those lines.

How do I reference tables in Excel using VBA?

In addition, it's convenient to define variables referring to objects. For instance,

Sub CreateTable()
    Dim lo as ListObject
    Set lo = ActiveSheet.ListObjects.Add(xlSrcRange, Range("$B$1:$D$16"), , xlYes)
    lo.Name = "Table1"
    lo.TableStyle = "TableStyleLight2"
    ...
End Sub

You will probably find it advantageous at once.

Defining Z order of views of RelativeLayout in Android

If you want to do this in code you can do

View.bringToFront();

see docs

Understanding dispatch_async

All of the DISPATCH_QUEUE_PRIORITY_X queues are concurrent queues (meaning they can execute multiple tasks at once), and are FIFO in the sense that tasks within a given queue will begin executing using "first in, first out" order. This is in comparison to the main queue (from dispatch_get_main_queue()), which is a serial queue (tasks will begin executing and finish executing in the order in which they are received).

So, if you send 1000 dispatch_async() blocks to DISPATCH_QUEUE_PRIORITY_DEFAULT, those tasks will start executing in the order you sent them into the queue. Likewise for the HIGH, LOW, and BACKGROUND queues. Anything you send into any of these queues is executed in the background on alternate threads, away from your main application thread. Therefore, these queues are suitable for executing tasks such as background downloading, compression, computation, etc.

Note that the order of execution is FIFO on a per-queue basis. So if you send 1000 dispatch_async() tasks to the four different concurrent queues, evenly splitting them and sending them to BACKGROUND, LOW, DEFAULT and HIGH in order (ie you schedule the last 250 tasks on the HIGH queue), it's very likely that the first tasks you see starting will be on that HIGH queue as the system has taken your implication that those tasks need to get to the CPU as quickly as possible.

Note also that I say "will begin executing in order", but keep in mind that as concurrent queues things won't necessarily FINISH executing in order depending on length of time for each task.

As per Apple:

https://developer.apple.com/library/content/documentation/General/Conceptual/ConcurrencyProgrammingGuide/OperationQueues/OperationQueues.html

A concurrent dispatch queue is useful when you have multiple tasks that can run in parallel. A concurrent queue is still a queue in that it dequeues tasks in a first-in, first-out order; however, a concurrent queue may dequeue additional tasks before any previous tasks finish. The actual number of tasks executed by a concurrent queue at any given moment is variable and can change dynamically as conditions in your application change. Many factors affect the number of tasks executed by the concurrent queues, including the number of available cores, the amount of work being done by other processes, and the number and priority of tasks in other serial dispatch queues.

Basically, if you send those 1000 dispatch_async() blocks to a DEFAULT, HIGH, LOW, or BACKGROUND queue they will all start executing in the order you send them. However, shorter tasks may finish before longer ones. Reasons behind this are if there are available CPU cores or if the current queue tasks are performing computationally non-intensive work (thus making the system think it can dispatch additional tasks in parallel regardless of core count).

The level of concurrency is handled entirely by the system and is based on system load and other internally determined factors. This is the beauty of Grand Central Dispatch (the dispatch_async() system) - you just make your work units as code blocks, set a priority for them (based on the queue you choose) and let the system handle the rest.

So to answer your above question: you are partially correct. You are "asking that code" to perform concurrent tasks on a global concurrent queue at the specified priority level. The code in the block will execute in the background and any additional (similar) code will execute potentially in parallel depending on the system's assessment of available resources.

The "main" queue on the other hand (from dispatch_get_main_queue()) is a serial queue (not concurrent). Tasks sent to the main queue will always execute in order and will always finish in order. These tasks will also be executed on the UI Thread so it's suitable for updating your UI with progress messages, completion notifications, etc.

How to take the first N items from a generator or list?

With itertools you will obtain another generator object so in most of the cases you will need another step the take the first N elements (N). There are at least two simpler solutions (a little bit less efficient in terms of performance but very handy) to get the elements ready to use from a generator:

Using list comprehension:

first_N_element=[generator.next() for i in range(N)]

Otherwise:

first_N_element=list(generator)[:N]

Where N is the number of elements you want to take (e.g. N=5 for the first five elements).

Simple tool to 'accept theirs' or 'accept mine' on a whole file using git

Based on Jakub's answer you can configure the following git aliases for convenience:

accept-ours = "!f() { git checkout --ours -- \"${@:-.}\"; git add -u \"${@:-.}\"; }; f"
accept-theirs = "!f() { git checkout --theirs -- \"${@:-.}\"; git add -u \"${@:-.}\"; }; f"

They optionally take one or several paths of files to resolve and default to resolving everything under the current directory if none are given.

Add them to the [alias] section of your ~/.gitconfig or run

git config --global alias.accept-ours '!f() { git checkout --ours -- "${@:-.}"; git add -u "${@:-.}"; }; f'
git config --global alias.accept-theirs '!f() { git checkout --theirs -- "${@:-.}"; git add -u "${@:-.}"; }; f'

How to convert InputStream to FileInputStream

Long story short: Don't use FileInputStream as a parameter or variable type. Use the abstract base class, in this case InputStream instead.

dynamically add and remove view to viewpager

I was looking for simple solution to remove views from viewpager (no fragments) dynamically. So, if you have some info, that your pages belongs to, you can set it to View as tag. Just like that (adapter code):

@Override
public Object instantiateItem(ViewGroup collection, int position)
{
    ImageView iv = new ImageView(mContext);
    MediaMessage msg = mMessages.get(position);
    ...

    iv.setTag(media);
    return iv;
}

@Override
public int getItemPosition (Object object)
{
    View o = (View) object;
    int index = mMessages.indexOf(o.getTag());
    if (index == -1)
        return POSITION_NONE;
    else
        return index;
}

You just need remove your info from mMessages, and then call notifyDataSetChanged() for your adapter. Bad news there is no animation in this case.

SQL Server: SELECT only the rows with MAX(DATE)

SELECT t1.OrderNo, t1.PartCode, t1.Quantity
FROM table AS t1
INNER JOIN (SELECT OrderNo, MAX(DateEntered) AS MaxDate
            FROM table
            GROUP BY OrderNo) AS t2
ON (t1.OrderNo = t2.OrderNo AND t1.DateEntered = t2.MaxDate)

The inner query selects all OrderNo with their maximum date. To get the other columns of the table, you can join them on OrderNo and the MaxDate.

How to display a json array in table format?

var data = [
    {
        id : "001",
        name : "apple",
        category : "fruit",
        color : "red"
    },
    {
        id : "002",
        name : "melon",
        category : "fruit",
        color : "green"
    },
    {
        id : "003",
        name : "banana",
        category : "fruit",
        color : "yellow"
    }
];

for(var i = 0, len = data.length; i < length; i++) {
    var temp = '<tr><td>' + data[i].id + '</td>';
    temp+= '<td>' + data[i].name+ '</td>';
    temp+= '<td>' + data[i].category + '</td>';
    temp+= '<td>' + data[i].color + '</td></tr>';
    $('table tbody').append(temp));
}

Android turn On/Off WiFi HotSpot programmatically

Here's the complete solution if you want to implement the wifi hotspot feature programmatically in your android app.

SOLUTION FOR API < 26:

For devices < API 26. There is no public API by Android for this purpose. So, in order to work with those APIs you've to access private APIs through reflection. It is not recommended but if you've no other options left, then here's a trick.

First of all, you need to have this permission in your manifest,

  <uses-permission  
  android:name="android.permission.WRITE_SETTINGS"  
  tools:ignore="ProtectedPermissions"/>

  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
  <uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
  <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

Here's how you can ask it on run-time:

 private boolean showWritePermissionSettings() {    
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M  
    && Build.VERSION.SDK_INT < Build.VERSION_CODES.O) { 
  if (!Settings.System.canWrite(this)) {    
    Log.v("DANG", " " + !Settings.System.canWrite(this));   
    Intent intent = new Intent(android.provider.Settings.ACTION_MANAGE_WRITE_SETTINGS); 
    intent.setData(Uri.parse("package:" + this.getPackageName()));  
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
    this.startActivity(intent); 
    return false;   
  } 
}   
return true; //Permission already given 
}

You can then access the setWifiEnabled method through reflection. This returns true if the action you asked for is being process correctly i.e. enabling/disabling hotspot.

     public boolean setWifiEnabled(WifiConfiguration wifiConfig, boolean enabled) { 
 WifiManager wifiManager;
try {   
  if (enabled) { //disables wifi hotspot if it's already enabled    
    wifiManager.setWifiEnabled(false);  
  } 

   Method method = wifiManager.getClass()   
      .getMethod("setWifiApEnabled", WifiConfiguration.class, boolean.class);   
  return (Boolean) method.invoke(wifiManager, wifiConfig, enabled); 
} catch (Exception e) { 
  Log.e(this.getClass().toString(), "", e); 
  return false; 
}   
}

You can also get the wificonfiguration of your hotspot through reflection. I've answered that method for this question on StackOverflow.

P.S: If you don't want to turn on hotspot programmatically, you can start this intent and open the wifi settings screen for user to turn it on manually.

SOLUTION FOR API >= 26:

Finally, android released an official API for versions >= Oreo. You can just use the public exposed API by android i.e. startLocalOnlyHotspot

It turns on a local hotspot without internet access. Which thus can be used to host a server or transfer files.

It requires Manifest.permission.CHANGE_WIFI_STATE and ACCESS_FINE_LOCATION permissions.

Here's a simple example of how you can turn on hotspot using this API.

private WifiManager wifiManager;
WifiConfiguration currentConfig;
WifiManager.LocalOnlyHotspotReservation hotspotReservation;

The method to turn on hotspot:

@RequiresApi(api = Build.VERSION_CODES.O)
public void turnOnHotspot() {

      wifiManager.startLocalOnlyHotspot(new WifiManager.LocalOnlyHotspotCallback() {

        @Override
        public void onStarted(WifiManager.LocalOnlyHotspotReservation reservation) {
          super.onStarted(reservation);
          hotspotReservation = reservation;
          currentConfig = hotspotReservation.getWifiConfiguration();

          Log.v("DANG", "THE PASSWORD IS: "
              + currentConfig.preSharedKey
              + " \n SSID is : "
              + currentConfig.SSID);

          hotspotDetailsDialog();

        }

        @Override
        public void onStopped() {
          super.onStopped();
          Log.v("DANG", "Local Hotspot Stopped");
        }

        @Override
        public void onFailed(int reason) {
          super.onFailed(reason);
          Log.v("DANG", "Local Hotspot failed to start");
        }
      }, new Handler());
    }
`

Here's how you can get details of the locally created hotspot

private void hotspotDetaisDialog()
{

    Log.v(TAG, context.getString(R.string.hotspot_details_message) + "\n" + context.getString(
              R.string.hotspot_ssid_label) + " " + currentConfig.SSID + "\n" + context.getString(
              R.string.hotspot_pass_label) + " " + currentConfig.preSharedKey);

}

If it throws, a security exception even after giving the required permissions then you should try enabling your location using GPS. Here's the solution.

Recently, I've developed a demo app called Spotserve. That turns on wifi hotspot for all devices with API>=15 and hosts a demo server on that hotspot. You can check that for more details. Hope this helps!

How do I get the directory that a program is running from?

Just to belatedly pile on here,...

there is no standard solution, because the languages are agnostic of underlying file systems, so as others have said, the concept of a directory based file system is outside the scope of the c / c++ languages.

on top of that, you want not the current working directory, but the directory the program is running in, which must take into account how the program got to where it is - ie was it spawned as a new process via a fork, etc. To get the directory a program is running in, as the solutions have demonstrated, requires that you get that information from the process control structures of the operating system in question, which is the only authority on this question. Thus, by definition, its an OS specific solution.

Android - save/restore fragment state

Android fragment has some advantages and some disadvantages. The most disadvantage of the fragment is that when you want to use a fragment you create it ones. When you use it, onCreateView of the fragment is called for each time. If you want to keep state of the components in the fragment you must save fragment state and yout must load its state in the next shown. This make fragment view a bit slow and weird.

I have found a solution and I have used this solution: "Everything is great. Every body can try".

When first time onCreateView is being run, create view as a global variable. When second time you call this fragment onCreateView is called again you can return this global view. The fragment component state will be kept.

View view;

@Override
public View onCreateView(LayoutInflater inflater,
        @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    setActionBar(null);
    if (view != null) {
        if ((ViewGroup)view.getParent() != null)
            ((ViewGroup)view.getParent()).removeView(view);
        return view; 
    }
    view = inflater.inflate(R.layout.mylayout, container, false);
}

Stripping everything but alphanumeric chars from a string in Python

As a spin off from some other answers here, I offer a really simple and flexible way to define a set of characters that you want to limit a string's content to. In this case, I'm allowing alphanumerics PLUS dash and underscore. Just add or remove characters from my PERMITTED_CHARS as suits your use case.

PERMITTED_CHARS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-" 
someString = "".join(c for c in someString if c in PERMITTED_CHARS)

Regex, every non-alphanumeric character except white space or colon

This regex works for C#, PCRE and Go to name a few.

It doesn't work for JavaScript on Chrome from what RegexBuddy says. But there's already an example for that here.

This main part of this is:

\p{L}

which represents \p{L} or \p{Letter} any kind of letter from any language.`


The full regex itself: [^\w\d\s:\p{L}]

Example: https://regex101.com/r/K59PrA/2

Docker "ERROR: could not find an available, non-overlapping IPv4 address pool among the defaults to assign to the network"

  1. Check if any other container is running, If yes, do: docker-compose down
  2. If VPN is connected, then disconnect it and try again to up docker container:

    docker-compose up -d container_name
    

Two statements next to curly brace in an equation

That can be achieve in plain LaTeX without any specific package.

\documentclass{article}
\begin{document}
This is your only binary choices
\begin{math}
  \left\{
    \begin{array}{l}
      0\\
      1
    \end{array}
  \right.
\end{math}
\end{document}

This code produces something which looks what you seems to need.

curly braces in front of two lines

The same example as in the @Tombart can be obtained with similar code.

\documentclass{article}

\begin{document}

\begin{math}
  f(x)=\left\{
    \begin{array}{ll}
      1, & \mbox{if $x<0$}.\\
      0, & \mbox{otherwise}.
    \end{array}
  \right.
\end{math}

\end{document}

This code produces very similar results.

enter image description here

Correct set of dependencies for using Jackson mapper

The package names in Jackson 2.x got changed to com.fasterxml1 from org.codehaus2. So if you just need ObjectMapper, I think Jackson 1.X can satisfy with your needs.

Notepad++ change text color?

You can Change it from:

Menu Settings -> Style Configurator

See on screenshot:

enter image description here

OS X Bash, 'watch' command

To prevent flickering when your main command takes perceivable time to complete, you can capture the output and only clear screen when it's done.

function watch {while :; do a=$($@); clear; echo "$(date)\n\n$a"; sleep 1;  done}

Then use it by:

watch istats

How can I get input radio elements to horizontally align?

In your case, you just need to remove the line breaks (<br> tags) between the elements - input elements are inline-block by default (in Chrome at least). (updated example).

<input type="radio" name="editList" value="always">Always
<input type="radio" name="editList" value="never">Never
<input type="radio" name="editList" value="costChange">Cost Change

I'd suggest using <label> elements, though. In doing so, clicking on the label will check the element too. Either associate the <label>'s for attribute with the <input>'s id: (example)

<input type="radio" name="editList" id="always" value="always"/>
<label for="always">Always</label>

<input type="radio" name="editList" id="never" value="never"/>
<label for="never">Never</label>

<input type="radio" name="editList" id="change" value="costChange"/>
<label for="change">Cost Change</label>

..or wrap the <label> elements around the <input> elements directly: (example)

<label>
    <input type="radio" name="editList" value="always"/>Always
</label>
<label>
    <input type="radio" name="editList" value="never"/>Never
</label>
<label>
    <input type="radio" name="editList" value="costChange"/>Cost Change
</label>

You can also get fancy and use the :checked pseudo class.

How to set the timeout for a TcpClient?

If using async & await and desire to use a time out without blocking, then an alternative and simpler approach from the answer provide by mcandal is to execute the connect on a background thread and await the result. For example:

Task<bool> t = Task.Run(() => client.ConnectAsync(ipAddr, port).Wait(1000));
await t;
if (!t.Result)
{
   Console.WriteLine("Connect timed out");
   return; // Set/return an error code or throw here.
}
// Successful Connection - if we get to here.

See the Task.Wait MSDN article for more info and other examples.

How to embed a PDF viewer in a page?

pdf2htmlEX by coolwanglu is probably the best solution out there to convert a pdf file into html. You could do a simple convert and then embed the html page as an iframe or something similar.

Getting pids from ps -ef |grep keyword

I use

ps -C "keyword" -o pid=

This command should give you a PID number.

How to enable file upload on React's Material UI simple input?

newer MUI version:

<input
  accept="image/*"
  className={classes.input}
  style={{ display: 'none' }}
  id="raised-button-file"
  multiple
  type="file"
/>
<label htmlFor="raised-button-file">
  <Button variant="raised" component="span" className={classes.button}>
    Upload
  </Button>
</label> 

Running script upon login mac

  1. Create your shell script as login.sh in your $HOME folder.

  2. Paste the following one-line script into Script Editor:

    do shell script "$HOME/login.sh"

  3. Then save it as an application.

  4. Finally add the application to your login items.

If you want to make the script output visual, you can swap step 2 for this:

tell application "Terminal"
  activate
  do script "$HOME/login.sh"
end tell

If multiple commands are needed something like this can be used:

tell application "Terminal"
  activate
  do script "cd $HOME"
  do script "./login.sh" in window 1
end tell

Java: Unresolved compilation problem

The major part is correctly answered by Thorbjørn Ravn Andersen.

This answer tries to shed light on the remaining question: how could the class file with errors end up in the jar?

Each build (mvn&javac or eclipse) signals in its specific way when it hits a compile error, and will refuse to create a Jar file from it (or at least prominently alert you). The most likely cause for silently getting class files with errors into a jar is by concurrent operation of Maven and Eclipse.

If you have Eclipse open while running a mvn build, you should disable Project > Build Automatically until mvn completes.

EDIT: Let's try to split the riddle into three parts:

(1) What is the meaning of "java.lang.Error: Unresolved compilation problem"

This has been explained by Thorbjørn Ravn Andersen. There is no doubt that Eclipse found an error at compile time.

(2) How can an eclipse-compiled class file end up in jar file created by maven (assuming maven is not configured to used ecj for compilation)?

This could happen either by invoking maven with no or incomplete cleaning. Or, an automatic Eclipse build could react to changes in the filesystem (done by maven) and re-compile a class, before maven proceeds to collect class files into the jar (this is what I meant by "concurrent operation" in my original answer).

(3) How come there is a compile error, but mvn clean succeeds?

Again several possibilities: (a) compilers don't agree whether or not the source code is legal, or (b) Eclipse compiles with broken settings like incomplete classpath, wrong Java compliance etc. Either way a sequence of refresh and clean build in Eclipse should surface the problem.

Upload Image using POST form data in Python-requests

Use this snippet

import os
import requests
url = 'http://host:port/endpoint'
with open(path_img, 'rb') as img:
  name_img= os.path.basename(path_img)
  files= {'image': (name_img,img,'multipart/form-data',{'Expires': '0'}) }
  with requests.Session() as s:
    r = s.post(url,files=files)
    print(r.status_code)

How to enable and use HTTP PUT and DELETE with Apache2 and PHP?

You can just post the file name to delete to delete.php on the server, which can easily unlink() the file.

How to test if a double is zero?

Yes, it's a valid test although there's an implicit conversion from int to double. For clarity/simplicity you should use (foo.x == 0.0) to test. That will hinder NAN errors/division by zero, but the double value can in some cases be very very very close to 0, but not exactly zero, and then the test will fail (I'm talking about in general now, not your code). Division by that will give huge numbers.

If this has anything to do with money, do not use float or double, instead use BigDecimal.

SyntaxError: multiple statements found while compiling a single statement

In the shell, you can't execute more than one statement at a time:

>>> x = 5
y = 6
SyntaxError: multiple statements found while compiling a single statement

You need to execute them one by one:

>>> x = 5
>>> y = 6
>>>

When you see multiple statements are being declared, that means you're seeing a script, which will be executed later. But in the interactive interpreter, you can't do more than one statement at a time.

Arrays.fill with multidimensional array in Java

In simple words java donot provide such an API. You need to iterate through loop and using fill method you can fill 2D array with one loop.

      int row = 5;
      int col = 6;
      int cache[][]=new int[row][col];
      for(int i=0;i<=row;i++){
          Arrays.fill(cache[i]);
      }

Why does 'git commit' not save my changes?

The reason why this is happening is because you have a folder that is already being tracked by Git inside another folder that is also tracked by Git. For example, I had a project and I added a subfolder to it. Both of them were being tracked by Git before I put one inside the other. In order to stop tracking the one inside, find it and remove the Git file with:

rm -rf .git

In my case I had a WordPress application and the folder I added inside was a theme. So I had to go to the theme root, and remove the Git file, so that the whole project would now be tracked by the parent, the WordPress application.

updating table rows in postgres using subquery

There are many ways to update the rows.

When it comes to UPDATE the rows using subqueries, you can use any of these approaches.

  1. Approach-1 [Using direct table reference]
UPDATE
  <table1>
SET
  customer=<table2>.customer,
  address=<table2>.address,
  partn=<table2>.partn
FROM
  <table2>
WHERE
  <table1>.address_id=<table2>.address_i;

Explanation: table1 is the table which we want to update, table2 is the table, from which we'll get the value to be replaced/updated. We are using FROM clause, to fetch the table2's data. WHERE clause will help to set the proper data mapping.

  1. Approach-2 [Using SubQueries]
UPDATE
  <table1>
SET
  customer=subquery.customer,
  address=subquery.address,
  partn=subquery.partn
FROM
  (
    SELECT
      address_id, customer, address, partn
    FROM  /* big hairy SQL */ ...
  ) AS subquery
WHERE
  dummy.address_id=subquery.address_id;

Explanation: Here we are using subquerie inside the FROM clause, and giving an alias to it. So that it will act like the table.

  1. Approach-3 [Using multiple Joined tables]
UPDATE
  <table1>
SET
  customer=<table2>.customer,
  address=<table2>.address,
  partn=<table2>.partn
FROM
  <table2> as t2
  JOIN <table3> as t3
  ON
    t2.id = t3.id
WHERE
  <table1>.address_id=<table2>.address_i;

Explanation: Sometimes we face the situation in that table join is so important to get proper data for the update. To do so, Postgres allows us to Join multiple tables inside the FROM clause.

  1. Approach-4 [Using WITH statement]

    • 4.1 [Using simple query]
WITH subquery AS (
    SELECT
      address_id,
      customer,
      address,
      partn
    FROM
      <table1>;
)
UPDATE <table-X>
SET customer = subquery.customer,
    address  = subquery.address,
    partn    = subquery.partn
FROM subquery
WHERE <table-X>.address_id = subquery.address_id;
  • 4.2 [Using query with complex JOIN]
WITH subquery AS (
    SELECT address_id, customer, address, partn
    FROM
      <table1> as t1
    JOIN
      <table2> as t2
    ON
      t1.id = t2.id;
    -- You can build as COMPLEX as this query as per your need.
)
UPDATE <table-X>
SET customer = subquery.customer,
    address  = subquery.address,
    partn    = subquery.partn
FROM subquery
WHERE <table-X>.address_id = subquery.address_id;

Explanation: From Postgres 9.1, this(WITH) concept has been introduces. Using that We can make any complex queries and generate desire result. Here we are using this approach to update the table.

I hope, this would be helpful.

Check if enum exists in Java

Most of the answers suggest either using a loop with equals to check if the enum exists or using try/catch with enum.valueOf(). I wanted to know which method is faster and tried it. I am not very good at benchmarking, so please correct me if I made any mistakes.

Heres the code of my main class:

    package enumtest;

public class TestMain {

    static long timeCatch, timeIterate;
    static String checkFor;
    static int corrects;

    public static void main(String[] args) {
        timeCatch = 0;
        timeIterate = 0;
        TestingEnum[] enumVals = TestingEnum.values();
        String[] testingStrings = new String[enumVals.length * 5];
        for (int j = 0; j < 10000; j++) {
            for (int i = 0; i < testingStrings.length; i++) {
                if (i % 5 == 0) {
                    testingStrings[i] = enumVals[i / 5].toString();
                } else {
                    testingStrings[i] = "DOES_NOT_EXIST" + i;
                }
            }

            for (String s : testingStrings) {
                checkFor = s;
                if (tryCatch()) {
                    ++corrects;
                }
                if (iterate()) {
                    ++corrects;
                }
            }
        }

        System.out.println(timeCatch / 1000 + "us for try catch");
        System.out.println(timeIterate / 1000 + "us for iterate");
        System.out.println(corrects);
    }

    static boolean tryCatch() {
        long timeStart, timeEnd;
        timeStart = System.nanoTime();
        try {
            TestingEnum.valueOf(checkFor);
            return true;
        } catch (IllegalArgumentException e) {
            return false;
        } finally {
            timeEnd = System.nanoTime();
            timeCatch += timeEnd - timeStart;
        }

    }

    static boolean iterate() {
        long timeStart, timeEnd;
        timeStart = System.nanoTime();
        TestingEnum[] values = TestingEnum.values();
        for (TestingEnum v : values) {
            if (v.toString().equals(checkFor)) {
                timeEnd = System.nanoTime();
                timeIterate += timeEnd - timeStart;
                return true;
            }
        }
        timeEnd = System.nanoTime();
        timeIterate += timeEnd - timeStart;
        return false;
    }
}

This means, each methods run 50000 times the lenght of the enum I ran this test multiple times, with 10, 20, 50 and 100 enum constants. Here are the results:

  • 10: try/catch: 760ms | iteration: 62ms
  • 20: try/catch: 1671ms | iteration: 177ms
  • 50: try/catch: 3113ms | iteration: 488ms
  • 100: try/catch: 6834ms | iteration: 1760ms

These results were not exact. When executing it again, there is up to 10% difference in the results, but they are enough to show, that the try/catch method is far less efficient, especially with small enums.

Portable way to check if directory exists [Windows/Linux, C]

stat() works on Linux., UNIX and Windows as well:

#include <sys/types.h>
#include <sys/stat.h>

struct stat info;

if( stat( pathname, &info ) != 0 )
    printf( "cannot access %s\n", pathname );
else if( info.st_mode & S_IFDIR )  // S_ISDIR() doesn't exist on my windows 
    printf( "%s is a directory\n", pathname );
else
    printf( "%s is no directory\n", pathname );

Remove border from IFrame

Its simple just add attribute in iframe tag frameborder = 0 <iframe src="" width="200" height="200" frameborder="0"></iframe>

Angular 2 : No NgModule metadata found

I'll give you few suggestions.Remove all these as mentioned below

1)<script src="polyfills.bundle.js"></script>(index.html)  //<<<===not sure as Angular2.0 final version doesn't require this.

2)platform.bootstrapModule(App); (main.ts)

3)import { NgModule } from '@angular/core'; (app.ts)

A fast way to delete all rows of a datatable at once

If you are running your code against a sqlserver database then
use this command

string sqlTrunc = "TRUNCATE TABLE " + yourTableName
SqlCommand cmd = new SqlCommand(sqlTrunc, conn);
cmd.ExecuteNonQuery();

this will be the fastest method and will delete everything from your table and reset the identity counter to zero.

The TRUNCATE keyword is supported also by other RDBMS.

5 years later:
Looking back at this answer I need to add something. The answer above is good only if you are absolutely sure about the source of the value in the yourTableName variable. This means that you shouldn't get this value from your user because he can type anything and this leads to Sql Injection problems well described in this famous comic strip. Always present your user a choice between hard coded names (tables or other symbolic values) using a non editable UI.

IsNothing versus Is Nothing

I initially used IsNothing but I've been moving towards using Is Nothing in newer projects, mainly for readability. The only time I stick with IsNothing is if I'm maintaining code where that's used throughout and I want to stay consistent.

Why do access tokens expire?

It is essentially a security measure. If your app is compromised, the attacker will only have access to the short-lived access token and no way to generate a new one.

Refresh tokens also expire but they are supposed to live much longer than the access token.

Detecting Browser Autofill

I had the same problem and I've written this solution.

It starts polling on every input field when the page is loading (I've set 10 seconds but you can tune this value).
After 10 seconds it stop polling on every input field and it starts polling only on the focused input (if one). It stops when you blur the input and again starts if you focus one.

In this way you poll only when really needed and only on a valid input.

// This part of code will detect autofill when the page is loading (username and password inputs for example)
var loading = setInterval(function() {
    $("input").each(function() {
        if ($(this).val() !== $(this).attr("value")) {
            $(this).trigger("change");
        }
    });
}, 100);
// After 10 seconds we are quite sure all the needed inputs are autofilled then we can stop checking them
setTimeout(function() {
    clearInterval(loading);
}, 10000);
// Now we just listen on the focused inputs (because user can select from the autofill dropdown only when the input has focus)
var focused;
$(document)
.on("focus", "input", function() {
    var $this = $(this);
    focused = setInterval(function() {
        if ($this.val() !== $this.attr("value")) {
            $this.trigger("change");
        }
    }, 100);
})
.on("blur", "input", function() {
    clearInterval(focused);
});

It does not work quite well when you have multiple values inserted automatically, but it could be tweaked looking for every input on the current form.

Something like:

// This part of code will detect autofill when the page is loading (username and password inputs for example)
var loading = setInterval(function() {
    $("input").each(function() {
        if ($(this).val() !== $(this).attr("value")) {
            $(this).trigger("change");
        }
    });
}, 100);
// After 10 seconds we are quite sure all the needed inputs are autofilled then we can stop checking them
setTimeout(function() {
    clearInterval(loading);
}, 10000);
// Now we just listen on inputs of the focused form
var focused;
$(document)
.on("focus", "input", function() {
    var $inputs = $(this).parents("form").find("input");
    focused = setInterval(function() {
        $inputs.each(function() {
            if ($(this).val() !== $(this).attr("value")) {
                $(this).trigger("change");
            }
        });
    }, 100);
})
.on("blur", "input", function() {
    clearInterval(focused);
});

Javascript callback when IFRAME is finished loading?

I had a similar problem as you. What I did is that I use something called jQuery. What you then do in the javascript code is this:

$(function(){ //this is regular jQuery code. It waits for the dom to load fully the first time you open the page.

    $("#myIframeId").load(function(){
       callback($("#myIframeId").html());
       $("#myIframeId").remove();

    });

});

It seems as you delete you iFrame before you grab the html from it. Now, I do see a problem with that :p

Hope this helps :).

git replacing LF with CRLF

In vim open the file (e.g.: :e YOURFILEENTER), then

:set noendofline binary
:wq

How to display a pdf in a modal window?

You can do this using with jQuery UI dialog, you can download JQuery ui from here Download JQueryUI

Include these scripts first inside <head> tag

<link href="css/smoothness/jquery-ui-1.9.0.custom.css" rel="stylesheet">
<script language="javascript" type="text/javascript" src="jquery-1.8.2.js"></script>
<script src="js/jquery-ui-1.9.0.custom.js"></script>

JQuery code

<script language="javascript" type="text/javascript">
  $(document).ready(function() {
    $('#trigger').click(function(){
      $("#dialog").dialog();
    }); 
  });                  
</script>

HTML code within <body> tag. Use an iframe to load the pdf file inside

<a href="#" id="trigger">this link</a>
<div id="dialog" style="display:none">
    <div>
    <iframe src="yourpdffile.pdf"></iframe>
    </div>
</div> 

What is the LD_PRELOAD trick?

As many people mentioned, using LD_PRELOAD to preload library. BTW, you can CHECK if the setting is available by ldd command.

Example: suppose you need to preload your own libselinux.so.1.

> ldd /bin/ls
    ...
    libselinux.so.1 => /lib/x86_64-linux-gnu/libselinux.so.1 (0x00007f3927b1d000)
    libacl.so.1 => /lib/x86_64-linux-gnu/libacl.so.1 (0x00007f3927914000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f392754f000)
    libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007f3927311000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f392710c000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f3927d65000)
    libattr.so.1 => /lib/x86_64-linux-gnu/libattr.so.1 (0x00007f3926f07000)

Thus, set your preload environment:

  export LD_PRELOAD=/home/patric/libselinux.so.1

Check your library again:

>ldd /bin/ls
    ...
    libselinux.so.1 =>
    /home/patric/libselinux.so.1 (0x00007fb9245d8000)
    ...

How to extract year and month from date in PostgreSQL without using to_char() function?

It is working for "greater than" functions not for less than.

For example:

select date_part('year',txndt)
from "table_name"
where date_part('year',txndt) > '2000' limit 10;

is working fine.

but for

select date_part('year',txndt)
from "table_name"
where date_part('year',txndt) < '2000' limit 10;

I am getting error.

How to implement DrawerArrowToggle from Android appcompat v7 21 library

First, you should know now the android.support.v4.app.ActionBarDrawerToggle is deprecated.

You must replace that with android.support.v7.app.ActionBarDrawerToggle.

Here is my example and I use the new Toolbar to replace the ActionBar.

MainActivity.java

public class MainActivity extends ActionBarActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(mToolbar);
    DrawerLayout mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(
        this,  mDrawerLayout, mToolbar,
        R.string.navigation_drawer_open, R.string.navigation_drawer_close
    );
    mDrawerLayout.setDrawerListener(mDrawerToggle);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setHomeButtonEnabled(true);
    mDrawerToggle.syncState();
}

styles.xml

<style name="AppTheme" parent="Theme.AppCompat.Light">
    <item name="drawerArrowStyle">@style/DrawerArrowStyle</item>
</style>

<style name="DrawerArrowStyle" parent="Widget.AppCompat.DrawerArrowToggle">
    <item name="spinBars">true</item>
    <item name="color">@android:color/white</item>
</style>

You can read the documents on AndroidDocument#DrawerArrowToggle_spinBars

This attribute is the key to implement the menu-to-arrow animation.

public static int DrawerArrowToggle_spinBars

Whether bars should rotate or not during transition
Must be a boolean value, either "true" or "false".

So, you set this: <item name="spinBars">true</item>.

Then the animation can be presented.

Hope this can help you.

MongoDB logging all queries

I ended up solving this by starting mongod like this (hammered and ugly, yeah... but works for development environment):

mongod --profile=1 --slowms=1 &

This enables profiling and sets the threshold for "slow queries" as 1ms, causing all queries to be logged as "slow queries" to the file:

/var/log/mongodb/mongodb.log

Now I get continuous log outputs using the command:

tail -f /var/log/mongodb/mongodb.log

An example log:

Mon Mar  4 15:02:55 [conn1] query dendro.quads query: { graph: "u:http://example.org/people" } ntoreturn:0 ntoskip:0 nscanned:6 keyUpdates:0 locks(micros) r:73163 nreturned:6 reslen:9884 88ms

How to prevent downloading images and video files from my website?

I'd like to add a more philosophical comment. The whole intent of the internet, particularly the World Wide Web, is to share data. If you don't want people to download a picture/video/document, don't put it on the web. It's really that simple. Too many people think they can impose their own rules on an existing design. Those who want to post content on the web, and control its distribution, are looking to have their cake and eat it too.

Difference between null and empty string

When Object variables are initially used in a language like Java, they have absolutely no value at all - not zero, but literally no value - that is null

For instance: String s;

If you were to use s, it would actually have a value of null, because it holds absolute nothing.

An empty string, however, is a value - it is a string of no characters.

String s; //Inits to null
String a =""; //A blank string

Null is essentially 'nothing' - it's the default 'value' (to use the term loosely) that Java assigns to any Object variable that was not initialized.

Null isn't really a value - and as such, doesn't have properties. So, calling anything that is meant to return a value - such as .length(), will invariably return an error, because 'nothing' cannot have properties.

To go into more depth, by creating s1 = ""; you are initializing an object, which can have properties, and takes up relevant space in memory. By using s2; you are designating that variable name to be a String, but are not actually assigning any value at that point.

Python 3 TypeError: must be str, not bytes with sys.stdout.write()

Python 3 handles strings a bit different. Originally there was just one type for strings: str. When unicode gained traction in the '90s the new unicode type was added to handle Unicode without breaking pre-existing code1. This is effectively the same as str but with multibyte support.

In Python 3 there are two different types:

  • The bytes type. This is just a sequence of bytes, Python doesn't know anything about how to interpret this as characters.
  • The str type. This is also a sequence of bytes, but Python knows how to interpret those bytes as characters.
  • The separate unicode type was dropped. str now supports unicode.

In Python 2 implicitly assuming an encoding could cause a lot of problems; you could end up using the wrong encoding, or the data may not have an encoding at all (e.g. it’s a PNG image).
Explicitly telling Python which encoding to use (or explicitly telling it to guess) is often a lot better and much more in line with the "Python philosophy" of "explicit is better than implicit".

This change is incompatible with Python 2 as many return values have changed, leading to subtle problems like this one; it's probably the main reason why Python 3 adoption has been so slow. Since Python doesn't have static typing2 it's impossible to change this automatically with a script (such as the bundled 2to3).

  • You can convert str to bytes with bytes('h€llo', 'utf-8'); this should produce b'H\xe2\x82\xacllo'. Note how one character was converted to three bytes.
  • You can convert bytes to str with b'H\xe2\x82\xacllo'.decode('utf-8').

Of course, UTF-8 may not be the correct character set in your case, so be sure to use the correct one.

In your specific piece of code, nextline is of type bytes, not str, reading stdout and stdin from subprocess changed in Python 3 from str to bytes. This is because Python can't be sure which encoding this uses. It probably uses the same as sys.stdin.encoding (the encoding of your system), but it can't be sure.

You need to replace:

sys.stdout.write(nextline)

with:

sys.stdout.write(nextline.decode('utf-8'))

or maybe:

sys.stdout.write(nextline.decode(sys.stdout.encoding))

You will also need to modify if nextline == '' to if nextline == b'' since:

>>> '' == b''
False

Also see the Python 3 ChangeLog, PEP 358, and PEP 3112.


1 There are some neat tricks you can do with ASCII that you can't do with multibyte character sets; the most famous example is the "xor with space to switch case" (e.g. chr(ord('a') ^ ord(' ')) == 'A') and "set 6th bit to make a control character" (e.g. ord('\t') + ord('@') == ord('I')). ASCII was designed in a time when manipulating individual bits was an operation with a non-negligible performance impact.

2 Yes, you can use function annotations, but it's a comparatively new feature and little used.

How do I open an .exe from another C++ .exe?

Try this:

#include <windows.h>

int main ()

{
    system ("start notepad.exe") // As an example. Change [notepad] to any executable file //

    return 0 ;
}

Get text of label with jquery

It's simple, set a specific value for that label (XXXXXXX for example) and run it, open html source of output (in browser) and look for XXXXXXX, you will see something like this <span id="mylabel">XXXXXX</span> it's what you want, the ID of <span> (I think it's usually same as Label name in asp code) now you can get its value by innerHTML or another method in JQuery