Dynamic closure vs static closure

[Bill Baxter]

On Sat, Oct 25, 2008 at 6:30 PM, KennyTM~ <kennytm at gmail.com> wrote:
> Frank Benoit wrote:
>>
>> It is great to hear that this issue is getting solved.
>> How will be the now syntax?
>>
>> I wonder if the distinction between dynamic/static closure shall be done
>> on the calling site, or the called site.
>>
>> void foo( void delegate() dg ){
>> }
>> // -or-
>> void foo2( scope void delegate() dg ){
>> }
>>
>> void bar(){
>>  int i;
>>  foo({
>>    i++;
>>  });
>>  // -or-
>>  foo( scope {
>>    i++;
>>  });
>> }
>>
>> Because I think, the foo method/function signature has to define if the
>> delegate is escaping or not. The caller might not know it.
>>
>> If the signature defines this, the compiler can check that and give more
>> safety.
>
> It should done on the calling site (the point where delegates are created).
> Why the called function need to know if the delegate is a closure or not?
> What they can do is just call the delegate.

The problem is this

{
    float x = 3.14;
    bar( float delegate (float y){ return x*y ; } );
      // this delegate need to be allocated?
}

If bar is going to hold onto the delegate beyond the end of the scope,
then allocation is needed.  The author of bar() may be in a better
position to judge that than the caller of bar().  But I'm not sure if
that's the only kind of situation to be concerned about.  Are there
other cases where only caller knows which it should be?

--bb