6.6 Array Comprehension

Array comprehension in Haxe combines array declaration and loops to allow concise initialization of arrays. It is identified by for or while constructs:

class Main {
  static public function main() {
    var a = [for (i in 0...10) i];
    trace(a); // [0,1,2,3,4,5,6,7,8,9]

    var i = 0;
    var b = [while (i < 10) i++];
    trace(b); // [0,1,2,3,4,5,6,7,8,9]
  }
}

Variable a is initialized to an array holding the numbers 0 to 9. The compiler generates code which adds the value of each loop iteration to the array, so the following code would be equivalent:

var a = [];
for (i in 0...10) a.push(i);

Variable b is initialized to an array with the same values, but through a different comprehension style using while instead of for. Again, the following code would be equivalent:

var i = 0;
var b = [];
while(i < 10) b.push(i++);

The loop expression can be anything, including conditions and nested loops, so the following works as expected:

class Main {
  static public function main() {
    var a = [
      for (a in 1...11)
        for (b in 2...4)
          if (a % b == 0)
            a + "/" + b
    ];
    // [2/2,3/3,4/2,6/2,6/3,8/2,9/3,10/2]
    trace(a);
  }
}

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