121 lines
3.8 KiB
JavaScript
121 lines
3.8 KiB
JavaScript
//>>built
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// wrapped by build app
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define("dojox/lang/functional/tailrec", ["dijit","dojo","dojox","dojo/require!dojox/lang/functional/lambda,dojox/lang/functional/util"], function(dijit,dojo,dojox){
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dojo.provide("dojox.lang.functional.tailrec");
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dojo.require("dojox.lang.functional.lambda");
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dojo.require("dojox.lang.functional.util");
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// This module provides recursion combinators:
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// - a tail recursion combinator.
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// Acknoledgements:
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// - recursion combinators are inspired by Manfred von Thun's article
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// "Recursion Theory and Joy"
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// (http://www.latrobe.edu.au/philosophy/phimvt/joy/j05cmp.html)
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// Notes:
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// - recursion combinators produce a function, which implements
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// their respective recusion patterns. String lambdas are inlined, if possible.
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(function(){
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var df = dojox.lang.functional, inline = df.inlineLambda, _x ="_x";
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df.tailrec = function(
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/*Function|String|Array*/ cond,
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/*Function|String|Array*/ then,
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/*Function|String|Array*/ before){
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// summary:
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// Generates a function for the tail recursion pattern. This is the simplified
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// version of the linear recursive combinator without the "after" function,
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// and with the modified "before" function. All parameter functions are called
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// in the context of "this" object.
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// cond:
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// The lambda expression, which is used to detect the termination of recursion.
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// It accepts the same parameter as the generated recursive function itself.
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// This function should return "true", if the recursion should be stopped,
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// and the "then" part should be executed. Otherwise the recursion will proceed.
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// then:
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// The lambda expression, which is called upon termination of the recursion.
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// It accepts the same parameters as the generated recursive function itself.
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// The returned value will be returned as the value of the generated function.
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// before:
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// The lambda expression, which is called before the recursive step.
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// It accepts the same parameter as the generated recursive function itself,
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// and returns an array of arguments for the next recursive call of
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// the generated function.
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var c, t, b, cs, ts, bs, dict1 = {}, dict2 = {},
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add2dict = function(x){ dict1[x] = 1; };
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if(typeof cond == "string"){
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cs = inline(cond, _x, add2dict);
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}else{
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c = df.lambda(cond);
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cs = "_c.apply(this, _x)";
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dict2["_c=_t.c"] = 1;
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}
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if(typeof then == "string"){
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ts = inline(then, _x, add2dict);
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}else{
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t = df.lambda(then);
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ts = "_t.t.apply(this, _x)";
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}
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if(typeof before == "string"){
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bs = inline(before, _x, add2dict);
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}else{
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b = df.lambda(before);
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bs = "_b.apply(this, _x)";
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dict2["_b=_t.b"] = 1;
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}
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var locals1 = df.keys(dict1), locals2 = df.keys(dict2),
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f = new Function([], "var _x=arguments,_t=_x.callee,_c=_t.c,_b=_t.b".concat( // Function
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locals1.length ? "," + locals1.join(",") : "",
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locals2.length ? ",_t=_x.callee," + locals2.join(",") : t ? ",_t=_x.callee" : "",
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";for(;!",
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cs,
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";_x=",
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bs,
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");return ",
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ts
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));
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if(c){ f.c = c; }
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if(t){ f.t = t; }
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if(b){ f.b = b; }
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return f;
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};
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})();
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/*
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For documentation only:
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1) The original recursive version:
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var tailrec1 = function(cond, then, before){
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var cond = df.lambda(cond),
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then = df.lambda(then),
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before = df.lambda(before);
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return function(){
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if(cond.apply(this, arguments)){
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return then.apply(this, arguments);
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}
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var args = before.apply(this, arguments);
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return arguments.callee.apply(this, args);
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};
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};
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2) The original iterative version (before minification and inlining):
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var tailrec2 = function(cond, then, before){
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var cond = df.lambda(cond),
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then = df.lambda(then),
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before = df.lambda(before);
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return function(){
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var args = arguments;
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for(; !cond.apply(this, args); args = before.apply(this, args));
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return then.apply(this, args);
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};
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};
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*/
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});
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