Re: Closures: summarizing suggestions a bit...

Hi Slava, Hi all,

> --- Slava Pestov <[email protected]> wrote:
> 
> 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(...).
> 

-- 1 --
Is "myObj" the placeholder for an element of the list? Or is the list
element inserted as parameter to the call of foo? 

If the list element is "$_" (like Perl gibberish) the two alternatives 
could be expressed like:

   map(list, $_.@foo());

and 

   map(list, myObj.@foo($_));


-- 2 --
What I yet do not understand: How I would implement the map method as 
instance method of the list. The call would be something like:

   list.map(myObj@foo);

or

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

But the class?

   public class List {
      ...
      public List map( Closure closure ) {

      }

   }

Is that it?

Victor


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