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94 lines
3.0 KiB
JavaScript
94 lines
3.0 KiB
JavaScript
15 years ago
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dojo.provide("dojox.lang.functional.curry");
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dojo.require("dojox.lang.functional.lambda");
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// This module adds high-level functions and related constructs:
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// - currying and partial functions
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// - argument pre-processing: mixer and flip
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// Acknoledgements:
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// - partial() is based on work by Oliver Steele
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// (http://osteele.com/sources/javascript/functional/functional.js)
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// which was published under MIT License
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// Defined methods:
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// - take any valid lambda argument as the functional argument
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(function(){
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var df = dojox.lang.functional, ap = Array.prototype;
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var currying = function(/*Object*/ info){
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return function(){ // Function
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var args = info.args.concat(ap.slice.call(arguments, 0));
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if(arguments.length + info.args.length < info.arity){
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return currying({func: info.func, arity: info.arity, args: args});
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}
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return info.func.apply(this, args);
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};
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};
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dojo.mixin(df, {
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// currying and partial functions
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curry: function(/*Function|String|Array*/ f, /*Number?*/ arity){
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// summary: curries a function until the arity is satisfied, at
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// which point it returns the calculated value.
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f = df.lambda(f);
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arity = typeof arity == "number" ? arity : f.length;
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return currying({func: f, arity: arity, args: []}); // Function
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},
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arg: {}, // marker for missing arguments
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partial: function(/*Function|String|Array*/ f){
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// summary: creates a function where some arguments are bound, and
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// some arguments (marked as dojox.lang.functional.arg) are will be
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// accepted by the final function in the order they are encountered.
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// description: This method is used to produce partially bound
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// functions. If you want to change the order of arguments, use
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// dojox.lang.functional.mixer() or dojox.lang.functional.flip().
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var a = arguments, l = a.length, args = new Array(l - 1), p = [], i = 1, t;
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f = df.lambda(f);
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for(; i < l; ++i){
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t = a[i];
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args[i - 1] = t;
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if(t === df.arg){
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p.push(i - 1);
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}
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}
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return function(){ // Function
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var t = ap.slice.call(args, 0), // clone the array
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i = 0, l = p.length;
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for(; i < l; ++i){
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t[p[i]] = arguments[i];
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}
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return f.apply(this, t);
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};
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},
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// argument pre-processing
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mixer: function(/*Function|String|Array*/ f, /*Array*/ mix){
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// summary: changes the order of arguments using an array of
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// numbers mix --- i-th argument comes from mix[i]-th place
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// of supplied arguments.
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f = df.lambda(f);
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return function(){ // Function
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var t = new Array(mix.length), i = 0, l = mix.length;
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for(; i < l; ++i){
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t[i] = arguments[mix[i]];
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}
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return f.apply(this, t);
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};
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},
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flip: function(/*Function|String|Array*/ f){
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// summary: changes the order of arguments by reversing their
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// order.
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f = df.lambda(f);
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return function(){ // Function
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// reverse arguments
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var a = arguments, l = a.length - 1, t = new Array(l + 1), i = 0;
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for(; i <= l; ++i){
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t[l - i] = a[i];
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}
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return f.apply(this, t);
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};
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}
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});
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})();
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