- Author:
- David Nickerson <david.nickerson@gmail.com>
- Date:
- 2021-09-17 15:39:51+12:00
- Desc:
- tweak html formatting
- Permanent Source URI:
- https://models.fieldml.org/workspace/a1/rawfile/c47db6b2fedb368422c7f4d5191aeb9f319ad684/dojo-presentation/js/dojo/dojox/lang/functional/fold.js
dojo.provide("dojox.lang.functional.fold");
dojo.require("dojox.lang.functional.lambda");
// This module adds high-level functions and related constructs:
// - "fold" family of functions
// Notes:
// - missing high-level functions are provided with the compatible API:
// foldl, foldl1, foldr, foldr1
// - missing JS standard functions are provided with the compatible API:
// reduce, reduceRight
// - the fold's counterpart: unfold
// 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 foldl, foldl1, and reduce)
(function(){
var d = dojo, df = dojox.lang.functional, empty = {};
d.mixin(df, {
// classic reduce-class functions
foldl: function(/*Array|String|Object*/ a, /*Function*/ 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 the final
// value.
if(typeof a == "string"){ a = a.split(""); }
o = o || d.global; f = df.lambda(f);
if(d.isArray(a)){
// array
for(var i = 0, n = a.length; i < n; z = f.call(o, z, a[i], i, a), ++i);
}else if(typeof a.hasNext == "function" && typeof a.next == "function"){
// iterator
for(var i = 0; a.hasNext(); z = f.call(o, z, a.next(), i++, a));
}else{
// object/dictionary
for(var i in a){
if(i in empty){ continue; }
z = f.call(o, z, a[i], i, a);
}
}
return z; // Object
},
foldl1: 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 the final value.
if(typeof a == "string"){ a = a.split(""); }
o = o || d.global; f = df.lambda(f);
var z;
if(d.isArray(a)){
// array
z = a[0];
for(var i = 1, n = a.length; i < n; z = f.call(o, z, a[i], i, a), ++i);
}else if(typeof a.hasNext == "function" && typeof a.next == "function"){
// iterator
if(a.hasNext()){
z = a.next();
for(var i = 1; a.hasNext(); z = f.call(o, z, a.next(), i++, a));
}
}else{
// object/dictionary
var first = true;
for(var i in a){
if(i in empty){ continue; }
if(first){
z = a[i];
first = false;
}else{
z = f.call(o, z, a[i], i, a);
}
}
}
return z; // Object
},
foldr: 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 the final
// value.
if(typeof a == "string"){ a = a.split(""); }
o = o || d.global; f = df.lambda(f);
for(var i = a.length; i > 0; --i, z = f.call(o, z, a[i], i, a));
return z; // Object
},
foldr1: function(/*Array|String*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: repeatedly applies a binary function to an array from right
// to left; returns the final value.
if(typeof a == "string"){ a = a.split(""); }
o = o || d.global; f = df.lambda(f);
var n = a.length, z = a[n - 1];
for(var i = n - 1; i > 0; --i, z = f.call(o, z, a[i], i, a));
return z; // Object
},
// JS 1.8 standard array functions, which can take a lambda as a parameter.
reduce: function(/*Array|String|Object*/ a, /*Function|String|Array*/ f, /*Object?*/ z){
// summary: apply a function simultaneously against two values of the array
// (from left-to-right) as to reduce it to a single value.
return arguments.length < 3 ? df.foldl1(a, f) : df.foldl(a, f, z); // Object
},
reduceRight: function(/*Array|String*/ a, /*Function|String|Array*/ f, /*Object?*/ z){
// summary: apply a function simultaneously against two values of the array
// (from right-to-left) as to reduce it to a single value.
return arguments.length < 3 ? df.foldr1(a, f) : df.foldr(a, f, z); // Object
},
// the fold's counterpart: unfold
unfold: function(/*Function|String|Array*/ pr, /*Function|String|Array*/ f,
/*Function|String|Array*/ g, /*Object*/ z, /*Object?*/ o){
// summary: builds an array by unfolding a value
o = o || d.global; f = df.lambda(f); g = df.lambda(g); pr = df.lambda(pr);
var t = [];
for(; !pr.call(o, z); t.push(f.call(o, z)), z = g.call(o, z));
return t; // Array
}
});
})();
