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NAME

Memoize - Make functions faster by trading space for time

SYNOPSIS

  JSAN.use('Memoize');

  memoize(slow_function);
  slow_function(arguments);    # Is faster than it was before

DESCRIPTION

This library implements the javscript version of Perl module Memoize, see http://search.cpan.org/dist/Memoize/ for concept about that. The name `Memoize' is given by the module author, Mark Jason Dominus.

`Memoizing' a function makes it faster by trading space for time. It does this by caching the return values of the function in a table. If you call the function again with the same arguments, memoize jumps in and gives you the value out of the table, instead of letting the function compute the value all over again.

METHODS

memoize()

This is the only function you should be calling. It takes one argument, the original function to be memoized, and the return the memoized version of that function.. It must be given as a function reference, like this:

  var f = function() {
      ...
  };
  f = memoized(f)

Or like this:

  var f = memoize(function() {
      ...
  });

Please be aware that, the "this" keyword inside the memoized function always refer to a null object. Which means you cannot just memoized an object method directly, instead, do something like this:

  var obj = new SomeObject();
  var f = function() {
    obj.slow_method()
  }
  f = memoize(f)
  // Use f to call obj.slow_method()

Which means, unlike Perl's Memoize module, the callers to the memoized function require to be modified to call the memoized function.

It is possible to use apply() or call() to simplify this snippet,

AUTHOR

Kang-min Liu <gugod@gugod.org>.

COPYRIGHT

Copyright 2006 by Kang-min Liu <gugod@gugod.org>.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See <http://www.perl.com/perl/misc/Artistic.html>

POD ERRORS

Hey! The above document had some coding errors, which are explained below:

Around line 30:

'=item' outside of any '=over'

Around line 63:

You forgot a '=back' before '=head1'

/**

*/

if ( typeof Memoize == 'undefined' ) {
    Memoize = function() {}
}

Memoize.VERSION = 0.02
Memoize.EXPORT  = [ 'memoize' ]
Memoize.EXPORT_TAGS = { ':all': Memoize.EXPORT }
Memoize.memoized = {}

Memoize.memoize = function(func) {
    if ( typeof func == 'function' ) {
        return function() {
            var memo = Memoize.the(func);
            var normalized_arg = Memoize.normalize( arguments );
            if ( typeof memo.cached_args[normalized_arg] == 'undefined') {
                memo.cached_args[normalized_arg] = memo["orig_function"].apply(null, arguments);
            }
            return memo.cached_args[normalized_arg]
        }
    }
}

Memoize.the = function(func) {
    if ( typeof Memoize.memoized[func] == 'undefined') {
        var memo = Memoize.memoized[func] = new Memoize();
        memo.orig_function = func
        memo.cached_args = {}
    }
    return Memoize.memoized[func]
}

Memoize.normalize= function(arg) {
    return Memoize.default_normzlier(arg)
}

Memoize.default_normzlier = function(arg) {
    var result = "";
    var separator = " ; ";
    for (var i = 0; i < arg.length; i++) {
        result += arg[i] + separator;
    }
    return result;
}

/**

*/