source: Dev/trunk/src/client/dojox/lang/functional/listcomp.js

dojo.provide("dojox.lang.functional.listcomp");

// This module adds high-level functions and related constructs:
//      - list comprehensions similar to JavaScript 1.7

// Notes:
//      - listcomp() produces functions, which after the compilation step are
//              as fast as regular JS functions (at least theoretically).

(function(){
        var g_re = /\bfor\b|\bif\b/gm;

        var listcomp = function(/*String*/ s){
                var frag = s.split(g_re), act = s.match(g_re),
                        head = ["var r = [];"], tail = [], i = 0, l = act.length;
                while(i < l){
                        var a = act[i], f = frag[++i];
                        if(a == "for" && !/^\s*\(\s*(;|var)/.test(f)){
                                f = f.replace(/^\s*\(/, "(var ");
                        }
                        head.push(a, f, "{");
                        tail.push("}");
                }
                return head.join("") + "r.push(" + frag[0] + ");" + tail.join("") + "return r;";        // String
        };

        dojo.mixin(dojox.lang.functional, {
                buildListcomp: function(/*String*/ s){
                        // summary:
                        //              builds a function from a text snippet, which represents a valid
                        //              JS 1.7 list comprehension, returns a string, which represents the function.
                        // description:
                        //              This method returns a textual representation of a function
                        //              built from the list comprehension text snippet (conformant to JS 1.7).
                        //              It is meant to be evaled in the proper context, so local variable can be
                        //              pulled from the environment.
                        return "function(){" + listcomp(s) + "}";       // String
                },
                compileListcomp: function(/*String*/ s){
                        // summary:
                        //              builds a function from a text snippet, which represents a valid
                        //              JS 1.7 list comprehension, returns a function object.
                        // description:
                        //              This method returns a function built from the list
                        //              comprehension text snippet (conformant to JS 1.7). It is meant to be
                        //              reused several times.
                        return new Function([], listcomp(s));   // Function
                },
                listcomp: function(/*String*/ s){
                        // summary:
                        //              executes the list comprehension building an array.
                        return (new Function([], listcomp(s)))();       // Array
                }
        });
})();