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

define(["dojo/_base/kernel", "dojo/_base/lang", "./lambda"], function(kernel, lang, df){

// This module adds high-level functions and related constructs:
//      - "scan" family of functions

// Notes:
//      - missing high-level functions are provided with the compatible API:
//              scanl, scanl1, scanr, scanr1

// Defined methods:
//      - take any valid lambda argument as the functional argument
//      - operate on dense arrays
//      - take a string as the array argument
//      - take an iterator objects as the array argument (only scanl, and scanl1)

        var empty = {};

        lang.mixin(df, {
                // classic reduce-class functions
                scanl: function(/*Array|String|Object*/ a, /*Function|String|Array*/ f, /*Object*/ z, /*Object?*/ o){
                        // summary:
                        //              repeatedly applies a binary function to an array from left
                        //              to right using a seed value as a starting point; returns an array
                        //              of values produced by foldl() at that point.
                        if(typeof a == "string"){ a = a.split(""); }
                        o = o || kernel.global; f = df.lambda(f);
                        var t, n, i;
                        if(lang.isArray(a)){
                                // array
                                t = new Array((n = a.length) + 1);
                                t[0] = z;
                                for(i = 0; i < n; z = f.call(o, z, a[i], i, a), t[++i] = z);
                        }else if(typeof a.hasNext == "function" && typeof a.next == "function"){
                                // iterator
                                t = [z];
                                for(i = 0; a.hasNext(); t.push(z = f.call(o, z, a.next(), i++, a)));
                        }else{
                                // object/dictionary
                                t = [z];
                                for(i in a){
                                        if(!(i in empty)){
                                                t.push(z = f.call(o, z, a[i], i, a));
                                        }
                                }
                        }
                        return t;       // Array
                },
                scanl1: function(/*Array|String|Object*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
                        // summary:
                        //              repeatedly applies a binary function to an array from left
                        //              to right; returns an array of values produced by foldl1() at that
                        //              point.
                        if(typeof a == "string"){ a = a.split(""); }
                        o = o || kernel.global; f = df.lambda(f);
                        var t, n, z, first = true;
                        if(lang.isArray(a)){
                                // array
                                t = new Array(n = a.length);
                                t[0] = z = a[0];
                                for(var i = 1; i < n; t[i] = z = f.call(o, z, a[i], i, a), ++i);
                        }else if(typeof a.hasNext == "function" && typeof a.next == "function"){
                                // iterator
                                if(a.hasNext()){
                                        t = [z = a.next()];
                                        for(i = 1; a.hasNext(); t.push(z = f.call(o, z, a.next(), i++, a)));
                                }
                        }else{
                                // object/dictionary
                                for(i in a){
                                        if(!(i in empty)){
                                                if(first){
                                                        t = [z = a[i]];
                                                        first = false;
                                                }else{
                                                        t.push(z = f.call(o, z, a[i], i, a));
                                                }
                                        }
                                }
                        }
                        return t;       // Array
                },
                scanr: function(/*Array|String*/ a, /*Function|String|Array*/ f, /*Object*/ z, /*Object?*/ o){
                        // summary:
                        //              repeatedly applies a binary function to an array from right
                        //              to left using a seed value as a starting point; returns an array
                        //              of values produced by foldr() at that point.
                        if(typeof a == "string"){ a = a.split(""); }
                        o = o || kernel.global; f = df.lambda(f);
                        var n = a.length, t = new Array(n + 1), i = n;
                        t[n] = z;
                        for(; i > 0; --i, z = f.call(o, z, a[i], i, a), t[i] = z);
                        return t;       // Array
                },
                scanr1: function(/*Array|String*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
                        // summary:
                        //              repeatedly applies a binary function to an array from right
                        //              to left; returns an array of values produced by foldr1() at that
                        //              point.
                        if(typeof a == "string"){ a = a.split(""); }
                        o = o || kernel.global; f = df.lambda(f);
                        var n = a.length, t = new Array(n), z = a[n - 1], i = n - 1;
                        t[i] = z;
                        for(; i > 0; --i, z = f.call(o, z, a[i], i, a), t[i] = z);
                        return t;       // Array
                }
        });
});