Yann Spöri

Accessing compilation date and git revision during compilation in HaXe

It is often useful if a program knows the time when it was build and/or the git repository revision id it was build from. Unfortunately, one often forgets to update this information before launching the build. The following code can be used to do this automatically.

(P.S.: The code works even when compiling towards “non-Sys” platforms like JavaScript.)

class BuildInfo {
     * The time when this library was build.
    public static var buildTime(default, null):Int = getBuildTime();

     * The git reversion that was used for the build.
    public static var gitRev(default, null):String = getGITRevision();

     * Macros initalizing the build information.
    public static macro function getBuildTime() {
        var buildTime = Math.floor(Date.now().getTime() / 1000);
        return macro $v{buildTime};
    public static macro function getGITRevision() {
        var gitrev = new sys.io.Process("git", [ "rev-parse", "--verify", "HEAD" ]).stdout.readAll().toString();
        return macro $v{gitrev};

    public static function main() {
        trace("This library was build the " + BuildInfo.buildTime);
        trace("by using revision " + BuildInfo.gitRev);
Posted by Yann Spöri in Haxe

The equal, equal operator in HaXe

The “==” operator to check object equality is implemented differently in the various programming languages. For example in Java, the “==” operator checks only the reference and you need the “equals”-Method in order to check the equality of objects:

String s1 = "foo";
String s2 = "foo";
System.out.println("" + (s1 == s2)); // will return false
System.out.println("" + (s1.equals(s2))); // will return true

In other languages like PHP, the “==”-operator can behave even more … strange …:

$a = "3.14159265358979326666666666";
$b = "3.14159265358979323846264338";
echo "" . ($a == $b); // will be 1 == true

So how is the “==”-operator defined in HaXe that can be cross-compiled into multiple languages including PHP and Java?

Well within Haxe, basic types like Int, Float, Strings and Bools are compared by values. So:

class Test {
    static function main() {
        var c1:String = "Hello";
        var c2:String = "World";
        trace(c1 == c2);  // will return false
        var c1:String = "Hello";
        var c2:String = "Hello";
        trace(c1 == c2);  // will return true

However nob basic types are compared by-reference:

class C { public function new() {} }

class Test {
    static function main() {
        var c1:C = null;
        var c2:C = null;
        trace(c1 == c2); // will return true
        var c1:C = new C();
        var c2:C = new C();
        trace(c1 == c2); // will return false
Posted by Yann Spöri in Haxe

Script user input


You want to remote control a program but unfortunately this program has only a “klick&gaudy”(*) interface.
(*) Okok – only has a graphical user interface (short GUI).


You may use xdotool in order to script user actions. To install this tool, use:

sudo apt-get install xdotool

Now you can get the position of the mouse pointer with:

xdotool getmouselocation

or set it via:

xdotool mousemove 400 300 (This means set the mouse to position x=400, y=300; Point of origin is the top left corner of the screen.)

In order to click use:

xdotool click 1

And in order to type a text (e.g. into a control field of the GUI)

xdotool type 'Hello World'

(P.S.: xdotool has much more options … Once this tool got installed type man xdotool in order to see them all.)

Posted by Yann Spöri in Allgemein

Play a sound in a Webbrowser


You want to play some sounds in a webbrowser.


Modern Browsers have a fancy integrated AudioContext that allows you to play sounds. Here is an example (JavaScript Code):

// get the AudioContext
window.AudioContext = window.AudioContext || window.webkitAudioContext;

// Initialize audio context
var context = new AudioContext();

// Create an oscillator ... via this oscillator we can then play different sounds
var oscillator = context.createOscillator();
oscillator.frequency.value = 440; // this is an "A"
oscillator.type = "square";

// attach the oscillator to the sound output

oscillator.start(0); // start the oscillator (0=now) ...
oscillator.stop(1);  // stop playing this sound after 1 second
Posted by Yann Spöri in Allgemein

Graph layouting via Graphviz


You want to display a Graph.


Create a simple text file describing your graph and save it with a .dot file extension:

graph {
node1 -- node2;
node2 -- node3;
node3 -- node4;
node4 -- node1;

Afterwards you can use a program of the graphviz package (sudo apt-get install graphviz) in order to visualize the graph. This package contains different layouting programs like dot, neato, fdp (all from the GraphViz project) etc. Simply call one of these programs in order to visualize the graph:

neato -Tsvg yourFile.dot -o outputFile.svg

Output from this command:

Posted by Yann Spöri in Allgemein

Uploading multiple files to the tornado webserver

The following html code can be used to create an html form that allows uploading multiple files at once:

<form enctype="multipart/form-data" method="POST" action="upload.py">
  <table style="width: 100%">
      <td>Choose the files to upload:</td>
      <td style="text-align: right"><input type="file" multiple="" id="files" name="files"></td>
      <td><input id="fileUploadButton" type="submit" value="Upload &gt;&gt;"></td>

Continue reading →

Posted by Yann Spöri in Python

LaTeX and special/chinese unicode characters


You want to create a pdf file (with latex) containing some chinese characters.

Continue reading →

Posted by Yann Spöri in LaTeX

Bash: TCP/Internet connection handling

There’re many problems nowadays, which could easier be solved through the internet. In this post I descripe how to address these problems by bash alone.

The standard way to connect to a server in the internet, is to embed the connection stream

exec 3<>/dev/tcp/$server/$ircPort || echo "Some text or doing, if connecting failed"

Continue reading →

Posted by Yann Spöri in Allgemein

Java FX: How to set the column constraint property using FXML


You have a Java FXML file document with a TableView and want to set the columnResizePolicy of this TableView in the fxml document.

Continue reading →

Posted by Yann Spöri in Allgemein