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functional.js
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if(!dojo._hasResource["dojox.lang.functional"]){ //_hasResource checks added by build. Do not use _hasResource directly in your code.
dojo._hasResource["dojox.lang.functional"] = true;
dojo.provide("dojox.lang.functional");
// This module adds high-level functions and related constructs:
// - list comprehensions similar to JavaScript 1.7
// - anonymous functions built from the string
// - zip combiners
// - "reduce" family of functions
// - currying and partial functions
// - argument pre-processing: mixer and flip
// - miscellaneous useful functions
// Acknoledgements:
// - parts of this module (most notably lambda, constFun, invoke, pluck, and partial)
// are based on work by Oliver Steele (http://osteele.com/sources/javascript/functional/functional.js)
// which was published under MIT License
// - Simple "maybe" monad was donated by Alex Russell.
// Notes:
// - Dojo provides following high-level functions in dojo/_base/array.js:
// forEach, map, filter, every, some
// - These functions implemented with optional lambda expression as a parameter.
// - missing high-level functions are provided with the compatible API:
// foldl, foldl1, scanl, scanl1, foldr, foldr1, scanr, scanr1,
// reduce, reduceRight
// - lambda() and listcomp() produce functions, which after the compilation step are
// as fast as regular JS functions (at least theoretically).
(function(){
var d = dojo, df = dojox.lang.functional, g_re = /\bfor\b|\bif\b/gm, empty = {};
// split() is augmented on IE6 to ensure the uniform behavior
var split = "ab".split(/a*/).length > 1 ? String.prototype.split :
function(sep){
var r = this.split.call(this, sep),
m = sep.exec(this);
if(m && m.index == 0){ r.unshift(""); }
return r;
};
var lambda = function(/*String*/ s){
var args = [], sects = split.call(s, /\s*->\s*/m);
if(sects.length > 1){
while(sects.length){
s = sects.pop();
args = sects.pop().split(/\s*,\s*|\s+/m);
if(sects.length){ sects.push("(function(" + args + "){return (" + s + ")})"); }
}
} else if(s.match(/\b_\b/)) {
args = ["_"];
} else {
var l = s.match(/^\s*(?:[+*\/%&|\^\.=<>]|!=)/m),
r = s.match(/[+\-*\/%&|\^\.=<>!]\s*$/m);
if(l || r){
if(l){
args.push("$1");
s = "$1" + s;
}
if(r){
args.push("$2");
s = s + "$2";
}
} else {
var vars = s.
replace(/(?:\b[A-Z]|\.[a-zA-Z_$])[a-zA-Z_$\d]*|[a-zA-Z_$][a-zA-Z_$\d]*:|this|true|false|null|undefined|typeof|instanceof|in|delete|new|void|arguments|decodeURI|decodeURIComponent|encodeURI|encodeURIComponent|escape|eval|isFinite|isNaN|parseFloat|parseInt|unescape|dojo|dijit|dojox|'(?:[^'\\]|\\.)*'|"(?:[^"\\]|\\.)*"/g, "").
match(/([a-z_$][a-z_$\d]*)/gi) || [];
var t = {};
d.forEach(vars, function(v){
if(!(v in t)){
args.push(v);
t[v] = 1;
}
});
}
}
return {args: args, body: "return (" + s + ");"}; // Object
};
var listcomp = function(/*String*/ s){
var frag = s.split(g_re), act = s.match(g_re),
head = ["var r = [];"], tail = [];
for(var i = 0; i < act.length;){
var a = act[i], f = frag[++i];
if(a == "for" && !/^\s*\(\s*(;|var)/.test(f)){
f = f.replace(/^\s*\(/, "(var ");
}
head.push(a, f, "{");
tail.push("}");
}
return head.join("") + "r.push(" + frag[0] + ");" + tail.join("") + "return r;"; // String
};
var currying = function(/*Object*/ info){
return function(){ // Function
if(arguments.length + info.args.length < info.arity){
return currying({func: info.func, arity: info.arity,
args: Array.prototype.concat.apply(info.args, arguments)});
}
return info.func.apply(this, Array.prototype.concat.apply(info.args, arguments));
};
};
var identity = function(x){ return x; };
var compose = function(/*Array*/ a){
return a.length ? function(){
var i = a.length - 1, x = df.lambda(a[i]).apply(this, arguments);
for(--i; i >= 0; --i){ x = df.lambda(a[i]).call(this, x); }
return x;
} : identity;
};
d.mixin(df, {
// lambda
buildLambda: function(/*String*/ s){
// summary: builds a function from a snippet, returns a string,
// which represents the function.
// description: This method returns a textual representation of a function
// built from the snippet. It is meant to be evaled in the proper context,
// so local variables can be pulled from the environment.
s = lambda(s);
return "function(" + s.args.join(",") + "){" + s.body + "}"; // String
},
lambda: function(/*Function|String|Array*/ s){
// summary: builds a function from a snippet, or array (composing), returns
// a function object; functions are passed through unmodified.
// description: This method is used to normalize a functional representation
// (a text snippet, an array, or a function) to a function object.
if(typeof s == "function"){ return s; }
if(s instanceof Array){ return compose(s); }
s = lambda(s);
return new Function(s.args, s.body); // Function
},
// sequence generators
repeat: function(/*Number*/ n, /*Function|String|Array*/ f, /*Object*/ z, /*Object?*/ o){
// summary: builds an array by repeatedly applying a unary function N times
// with a seed value Z.
o = o || d.global; f = df.lambda(f);
var t = new Array(n);
t[0] = z;
for(var i = 1; i < n; t[i] = z = f.call(o, z), ++i);
return t; // Array
},
until: function(/*Function|String|Array*/ pr, /*Function|String|Array*/ f, /*Object*/ z, /*Object?*/ o){
// summary: builds an array by repeatedly applying a unary function with
// a seed value Z until the predicate is satisfied.
o = o || d.global; f = df.lambda(f); pr = df.lambda(pr);
var t = [];
for(; !pr.call(o, z); t.push(z), z = f.call(o, z));
return t; // Array
},
buildListcomp: function(/*String*/ s){
// summary: builds a function from a text snippet, which represents a valid
// JS 1.7 list comprehension, returns a string, which represents the function.
// description: This method returns a textual representation of a function
// built from the list comprehension text snippet (conformant to JS 1.7).
// It is meant to be evaled in the proper context, so local variable can be
// pulled from the environment.
return "function(){" + listcomp(s) + "}"; // String
},
compileListcomp: function(/*String*/ s){
// summary: builds a function from a text snippet, which represents a valid
// JS 1.7 list comprehension, returns a function object.
// description: This method returns a function built from the list
// comprehension text snippet (conformant to JS 1.7). It is meant to be
// reused several times.
return new Function([], listcomp(s)); // Function
},
listcomp: function(/*String*/ s){
// summary: executes the list comprehension building an array.
return (new Function([], listcomp(s)))(); // Array
},
// classic reduce-class functions
foldl: function(/*Array*/ 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.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
for(var i = 0; i < a.length; z = f.call(o, z, a[i], i, a), ++i);
return z; // Object
},
foldl1: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: repeatedly applies a binary function to an array from left
// to right; returns the final value.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var z = a[0];
for(var i = 1; i < a.length; z = f.call(o, z, a[i], i, a), ++i);
return z; // Object
},
scanl: function(/*Array*/ 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.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length, t = new Array(n + 1);
t[0] = z;
for(var i = 0; i < n; z = f.call(o, z, a[i], i, a), t[++i] = z);
return t; // Array
},
scanl1: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object*/ z, /*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.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length, t = new Array(n), z = a[0];
t[0] = z;
for(var i = 1; i < n; z = f.call(o, z, a[i], i, a), t[i++] = z);
return t; // Array
},
foldr: function(/*Array*/ 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.
a = typeof a == "string" ? a.split("") : a; 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*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: repeatedly applies a binary function to an array from right
// to left; returns the final value.
a = typeof a == "string" ? a.split("") : a; 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
},
scanr: function(/*Array*/ 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.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length, t = new Array(n + 1);
t[n] = z;
for(var i = n; i > 0; --i, z = f.call(o, z, a[i], i, a), t[i] = z);
return t; // Array
},
scanr1: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object*/ z, /*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.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length, t = new Array(n), z = a[n - 1];
t[n - 1] = z;
for(var i = n - 1; i > 0; --i, z = f.call(o, z, a[i], i, a), t[i] = z);
return t; // Array
},
// JS 1.6 standard array functions, which can take a lambda as a parameter.
// Consider using dojo._base.array functions, if you don't need the lambda support.
filter: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: creates a new array with all elements that pass the test
// implemented by the provided function.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length, t = [], v;
for(var i = 0; i < n; ++i){
v = a[i];
if(f.call(o, v, i, a)){ t.push(v); }
}
return t; // Array
},
forEach: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: executes a provided function once per array element.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length;
for(var i = 0; i < n; f.call(o, a[i], i, a), ++i);
},
map: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: creates a new array with the results of calling
// a provided function on every element in this array.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length, t = new Array(n);
for(var i = 0; i < n; t[i] = f.call(o, a[i], i, a), ++i);
return t; // Array
},
every: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: tests whether all elements in the array pass the test
// implemented by the provided function.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length;
for(var i = 0; i < n; ++i){
if(!f.call(o, a[i], i, a)){
return false; // Boolean
}
}
return true; // Boolean
},
some: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: tests whether some element in the array passes the test
// implemented by the provided function.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
var n = a.length;
for(var i = 0; i < n; ++i){
if(f.call(o, a[i], i, a)){
return true; // Boolean
}
}
return false; // Boolean
},
// JS 1.8 standard array functions, which can take a lambda as a parameter.
reduce: function(/*Array*/ a, /*Function*/ 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*/ a, /*Function*/ 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
},
// 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, args = new Array(a.length - 1), p = [];
f = df.lambda(f);
for(var i = 1; i < a.length; ++i){
var t = a[i];
args[i - 1] = t;
if(t == df.arg){
p.push(i - 1);
}
}
return function(){ // Function
var t = Array.prototype.slice.call(args, 0); // clone the array
for(var i = 0; i < p.length; ++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);
for(var i = 0; i < mix.length; ++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;
for(i = 0; i <= l; ++i){
t[l - i] = a[i];
}
return f.apply(this, t);
};
},
// combiners
zip: function(){
// summary: returns an array of arrays, where the i-th array
// contains the i-th element from each of the argument arrays.
// description: This is the venerable zip combiner (for example,
// see Python documentation for general details). The returned
// array is truncated to match the length of the shortest input
// array.
var n = arguments[0].length, m = arguments.length, i;
for(i = 1; i < m; n = Math.min(n, arguments[i++].length));
var t = new Array(n), j;
for(i = 0; i < n; ++i){
var p = new Array(m);
for(j = 0; j < m; p[j] = arguments[j][i], ++j);
t[i] = p;
}
return t; // Array
},
unzip: function(/*Array*/ a){
// summary: similar to dojox.lang.functional.zip(), but takes
// a single array of arrays as the input.
// description: This function is similar to dojox.lang.functional.zip()
// and can be used to unzip objects packed by
// dojox.lang.functional.zip(). It is here mostly to provide
// a short-cut for the different method signature.
return df.zip.apply(null, a); // Array
},
// miscelaneous functional adapters
constFun: function(/*Object*/ x){
// summary: returns a function, which produces a constant value
// regardless of supplied parameters.
return function(){ return x; }; // Function
},
invoke: function(/*String*/ m){
// summary: returns a function, which invokes a method on supplied
// object using optional parameters.
return function(/*Object*/ o){ // Function
return o[m].apply(o, Array.prototype.slice.call(arguments, 1));
};
},
pluck: function(/*String*/ m){
// summary: returns a function, which returns a named object member.
return function(/*Object*/ o){ // Function
return o[m];
};
},
// object helpers
forIn: function(/*Object*/ obj, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: iterates over all object members skipping members, which
// are present in the empty object (IE and/or 3rd-party libraries).
o = o || d.global; f = df.lambda(f);
for(var i in obj){
if(i in empty){ continue; }
f.call(o, obj[i], i, obj);
}
},
forEachReversed: function(/*Array*/ a, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: executes a provided function once per array element.
a = typeof a == "string" ? a.split("") : a; o = o || d.global; f = df.lambda(f);
for(var i = a.length - 1; i >= 0; f.call(o, a[i], i, a), --i);
}
});
// monads
dojo.declare("dojox.lang.functional.MaybeMonad", null, {
constructor: function(/*Object*/ value){
// summary: constructs a monad optionally initializing all additional members
if(arguments.length){
this.value = value;
}
},
bind: function(/*dojox.lang.functional.Monad*/ monad, /*Function|String|Array*/ f, /*Object?*/ o){
// summary: this is the classic bind method, which applies a function to a monad,
// and returns a result as a monad; it is meant to be overwritten to incorporate
// side effects
if(!("value" in monad)){
return new this.constructor(); // dojox.lang.functional.MaybeMonad
}
// => possible side-effects go here
o = o || d.global; f = df.lambda(f);
return f.call(o, monad.value); // dojox.lang.functional.Monad
},
// class-specific methods
isNothing: function(){
// summary: check if there is no bound value.
return !("value" in this); // Boolean
}
});
df.MaybeMonad.returnMonad = function(/*Object*/ value){
// summary: puts a valye in the Maybe monad.
return new df.MaybeMonad(value); // dojox.lang.functional.MaybeMonad
};
df.MaybeMonad.zero = new df.MaybeMonad();
})();
}

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