- Author:
- David Nickerson <nickerso@users.sourceforge.net>
- Date:
- 2009-07-16 02:00:03+12:00
- Desc:
- the starting point for the HH tutorial example
- Permanent Source URI:
- https://models.fieldml.org/workspace/a1/rawfile/f6a8f90307388eb4b040ee3566b84d88b59247f7/dojo-presentation/js/dojo/dojox/lang/functional/lambda.js
dojo.provide("dojox.lang.functional.lambda");
// This module adds high-level functions and related constructs:
// - anonymous functions built from the string
// Acknoledgements:
// - lambda() is based on work by Oliver Steele
// (http://osteele.com/sources/javascript/functional/functional.js)
// which was published under MIT License
// Notes:
// - lambda() produces functions, which after the compilation step are
// as fast as regular JS functions (at least theoretically).
// Lambda input values:
// - returns functions unchanged
// - converts strings to functions
// - converts arrays to a functional composition
(function(){
var df = dojox.lang.functional;
// 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 + "$2";
}
}else{
// the point of the long regex below is to exclude all well-known
// lower-case words from the list of potential arguments
var vars = s.
replace(/(?:\b[A-Z]|\.[a-zA-Z_$])[a-zA-Z_$\d]*|[a-zA-Z_$][a-zA-Z_$\d]*:|this|true|false|null|undefined|typeof|instanceof|in|delete|new|void|arguments|decodeURI|decodeURIComponent|encodeURI|encodeURIComponent|escape|eval|isFinite|isNaN|parseFloat|parseInt|unescape|dojo|dijit|dojox|window|document|'(?:[^'\\]|\\.)*'|"(?:[^"\\]|\\.)*"/g, "").
match(/([a-z_$][a-z_$\d]*)/gi) || [];
var t = {};
dojo.forEach(vars, function(v){
if(!(v in t)){
args.push(v);
t[v] = 1;
}
});
}
}
return {args: args, body: s}; // Object
};
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
function(x){ return x; };
};
dojo.mixin(df, {
// lambda
rawLambda: function(/*String*/ s){
// summary: builds a function from a snippet, or array (composing), returns
// an object describing the function; functions are passed through unmodified.
// description: This method is to normalize a functional representation
// (a text snippet) to an object that contains an array of arguments,
// and a body , which is used to calculate the returning value.
return lambda(s); // Object
},
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(",") + "){return (" + 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, "return (" + s.body + ");"); // Function
}
});
})();
