Re: Closures: summarizing suggestions a bit...

Hi all,

I suggest a syntax for closures, somewhat inspired by Common Lisp, where 
refer to a function object, either named or anonymous, you write #'foo, 
where foo is either a function name, or an anonymous function block 
("lambda").

While #' is a bit ackward, in BeanShell you can reserve the 
currently-unused @ character to look up inside the function namespace -- 
giving the ability to have function object literals. Using @ in a C like 
language is not that weird, and Objective C uses this character.

So, suppose you had a function map() that took a list and a function, 
and returned a new list. You could do:

sq(x) { return x*x; }

map(list,@sq);

For anonymous closures, just use a syntax like

map(list,@(x) { return x*x; });

So its @(arguments) { body }

(in Common Lisp, its #'(lambda (x y) (+ x y)) -- notice the parallel...).

Now, I missed method literals. What you could do is return an object 
that is internally a pair; a 'this', and a BeanShell method to invoke. 
So the syntax could be like:

map(list,myObj.@foo);

Where myObj.@foo is an object that when called in some way, invokes 
myObj.foo(...).

To call a method, function or closure, i think its ok to call the 'do' 
method on it, like in SmallTalk.

void map(list,closure)
{
     for(i = 0; i < list.size(); i++)
         list.set(i,closure.do(list.get(i)));
}

I hope my proposal is considered. I think overloading an unused 
punctuation character is the best way to implement anonymous closures 
and methods-as-arguments while maintaining brevity, without creating 
ambiguous situations.

Patrick Niemeyer wrote:
> Just to summarize a few of the alternate suggestions:
> 
> // Extended method-like syntax:
> callable( ... );
> callable( arg, ... );
> 
> 
> // Anonymous inner class-like syntax:
> () { ... }
> (arg) { ... }
> 
> 
> // Multiple curly brace syntax:
> {{ ... }}
> { arg { ... } }
> 
> 
> 
> Pat
> 
> 
> 
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