source: Dev/trunk/src/client/dojox/lang/functional/curry.js @ 483

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

dojo.require("dojox.lang.functional.lambda");

// This module adds high-level functions and related constructs:
//      - currying and partial functions
//      - argument pre-processing: mixer and flip

// Acknowledgements:
//      - partial() is based on work by Oliver Steele
//              (http://osteele.com/sources/javascript/functional/functional.js)
//              which was published under MIT License

// Defined methods:
//      - take any valid lambda argument as the functional argument

(function(){
        var df = dojox.lang.functional, ap = Array.prototype;

        var currying = function(/*Object*/ info){
                return function(){      // Function
                        var args = info.args.concat(ap.slice.call(arguments, 0));
                        if(arguments.length + info.args.length < info.arity){
                                return currying({func: info.func, arity: info.arity, args: args});
                        }
                        return info.func.apply(this, args);
                };
        };

        dojo.mixin(df, {
                // currying and partial functions
                curry: function(/*Function|String|Array*/ f, /*Number?*/ arity){
                        // summary:
                        //              curries a function until the arity is satisfied, at
                        //              which point it returns the calculated value.
                        f = df.lambda(f);
                        arity = typeof arity == "number" ? arity : f.length;
                        return currying({func: f, arity: arity, args: []});     // Function
                },
                arg: {},        // marker for missing arguments
                partial: function(/*Function|String|Array*/ f){
                        // summary:
                        //              creates a function where some arguments are bound, and
                        //              some arguments (marked as dojox.lang.functional.arg) are will be
                        //              accepted by the final function in the order they are encountered.
                        // description:
                        //              This method is used to produce partially bound
                        //              functions. If you want to change the order of arguments, use
                        //              dojox.lang.functional.mixer() or dojox.lang.functional.flip().
                        var a = arguments, l = a.length, args = new Array(l - 1), p = [], i = 1, t;
                        f = df.lambda(f);
                        for(; i < l; ++i){
                                t = a[i];
                                args[i - 1] = t;
                                if(t === df.arg){
                                        p.push(i - 1);
                                }
                        }
                        return function(){      // Function
                                var t = ap.slice.call(args, 0), // clone the array
                                        i = 0, l = p.length;
                                for(; i < l; ++i){
                                        t[p[i]] = arguments[i];
                                }
                                return f.apply(this, t);
                        };
                },
                // argument pre-processing
                mixer: function(/*Function|String|Array*/ f, /*Array*/ mix){
                        // summary:
                        //              changes the order of arguments using an array of
                        //              numbers mix --- i-th argument comes from mix[i]-th place
                        //              of supplied arguments.
                        f = df.lambda(f);
                        return function(){      // Function
                                var t = new Array(mix.length), i = 0, l = mix.length;
                                for(; i < l; ++i){
                                        t[i] = arguments[mix[i]];
                                }
                                return f.apply(this, t);
                        };
                },
                flip: function(/*Function|String|Array*/ f){
                        // summary:
                        //              changes the order of arguments by reversing their
                        //              order.
                        f = df.lambda(f);
                        return function(){      // Function
                                // reverse arguments
                                var a = arguments, l = a.length - 1, t = new Array(l + 1), i = 0;
                                for(; i <= l; ++i){
                                        t[l - i] = a[i];
                                }
                                return f.apply(this, t);
                        };
                }
        });
})();