On Thu, Sep 18, 2008 at 10:41, Garrett Smith <[EMAIL PROTECTED]> wrote:
> 2008/9/18 Mark S. Miller <[EMAIL PROTECTED]>:
>> The Redmond mtg is fast approaching. We'd like to put out an official
>> for-Redmond-mtg draft of the ES3.1 spec by then. I had volunteered to write
>> the spec for Function.prototype.bind(). Long term, I think we all agree we'd
>> like to see this spec and many others self-hosted in EcmaScript. However,
>> the discussion of self-hosting issues makes clear that this ain't gonna
>> happen in time for ES3.1.
>>
>> So what we need now is a spec for Function.prototype.bind() in the peculiar
>> pseudo-code style -- combining the worst of COBOL and assembly language --
>
> What pseudo-code style? This:
>
> Function.prototype.bind( context, [ preArg1 [, preArg1 [,...]]])
>
> ?
>
>> used in the rest of the spec. Unfortunately, I won't have time between now
>> and then. Would anyone care to contribute some text? Please?
>>
>
> I'm not sure exactly what you're looking for so I've typed only a
> little. Is this in the right direction:-
>
> ================================================
> Function.prototype.bind( context, [ preArg1 [, preArg1 [,...]]])
>
> Returns a function that invokes this function. The |context| argument
> determines the execution context of the returned function. Arguments
> 1..n are used for values of parameter variables to this function.
>
> Example:
> var brendan = { name : "Brendan" };
> function sayHelloTo(name) {
> return "Hi " + name + ", my name is " + this.name + ".";
> }
>
> brendansGreeting = sayHelloTo.bind(brendan);
>
> brendansGreeting("Mark");
>
> returns
> "Hi Mark, my name is Brendan."
>
> Methods |Function.prototype.call| and |Function.prototype.apply| do
> not affect the |this| value of a bound function. Thus:
>
> brendansGreeting.call(null, "Mark");
>
> returns
> "Hi Mark, my name is Brendan."
>
> [insert_algorithm_steps_here]
>
> The |length| property of Function.prototype.bind is 1.
>
> ================================================
> A self-hosted version:
> /**
> * @param {Object} context the |this| value to be used.
> * @param {arguments} [1..n] optional arguments that are
> * prepended to returned function's call.
> * @return {Function} a function that uses |context| as the this
> * value for the returned function and arguments 1..n for values
> * of parameter variables to this function.
> */
> Function.prototype.bind = function(context) {
> var fn = this,
> ap, concat, args,
> isPartial = arguments.length > 1;
> // Strategy 1: just bind, not a partialApply
> if(!isPartial) {
> return function() {
> if(arguments.length !== 0) {
> return fn.apply(context, arguments);
> } else {
> return fn.call(context); // faster in Firefox.
> }
> };
> } else {
> // Strategy 2: partialApply
> ap = Array.prototype,
> args = ap.slice.call(arguments, 1);
> concat = ap.concat;
> return function() {
> return fn.apply(context,
> arguments.length === 0 ? args :
> concat.apply(args, arguments));
> };
> }
> };
There is really no point in exposing the two different cases in a
spec. A spec should describe the semantics, not the implementation.
> ================================================
>
> ?
>
> Garrett
>
>> --
>> Cheers,
>> --MarkM
>>
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>>
>>
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--
erik
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