Closures Syntax

Using closures in Code Orchestra performs two missions:

• Providing more compact syntax for anonymous functions.
• Enabling type safe behavior for functions.

##Syntactic Features

• function ( function ( parameters ) )

Closure syntax is very concise. Parameters type declaration is usually hidden. For readability and brevity, there is a special view for single-line closures – in such a closure a semi-colon on the end is omitted. Closures have also a special behavior – “the last statement is a return value” – which means you should use 1; (in the last line) instead of return 1;.

// declaring f1, f2 and f3
var f1 : {=>void};
var f2 : {int=>void};
var f3 : {String, String, int=>String};

// closure-style 
f1 = { =>  };
f2 = { p2 : int =>  };
// type declaration  is even more compact if you enumerate two parameters of a single type
f3 = { p1, p2 : String, p3 : int => "Hello" };

// the same code in a "classic" style f1 = function() : void { };

f2 = function(p1 : int) : void { };

f3 = function(p1 : String, p2 : String, p3: int) : String { return "Hello"; }; Type Safety

In the pure ActionScript3 each function can be only of a single type (also Function), no matter what value it returns, how many parameters it has or which type those parameters are.

var f : Function; // f can be of a Function type only

f = function() : void { }; // typesystem checks will not work here f = function(p1 : int) : void { }; // and you can always send a wrong parameter to a function f = function(p1 : String, p2 : int) : String {return "Hello"; }; // without any warning Closure is type safe, i.e. autocomplete and typesytem checks work here:

var f1 : {=>void}; // f1 doens't require any parameter and is void var f2 : {int=>void}; // f2 requires one integer argument and is void var f3 : {String, int=>String}; // f3 has two arguments and returns String

// using closures don't give you a chance to send a wrong parameter to a function

f1 = function() : void { }; // valid code f1 = function(a:int) : void { }; // wrong type, typesystem will report an error here f1 = function() : String { return "Hello!" }; // wrong type, typesystem will report an error here