DMD 1.038 and 2.022 releases

[Denis Koroskin]

On Tue, 16 Dec 2008 01:48:21 +0300, mastrost <titi.mastro at free.fr> wrote:

> Hi,
>
> first of all, thank you Walter and all the D community for making the  
> great "pure"
> feature become reality.
> I have 2 questions concerning the behaviour of this feature.
>
> The first one concerns the existence -or not- of "pure delegates".
> It makes sense to use a delegate if its closure is not empty -otherwise  
> it is no
> more than a function-. This is the reason why we can think delegates  
> cannot be
> pure. Let's take an example:
>
> void foo(){
>     int x=0;
>     //bar is not pure at all in this context
>     int bar(){
>         return x;
>     }
>     writefln(bar()); // prints '0'
>     ++x;
>     writefln(bar()); // prints '1'
> }
>
> But the fact is that when returning a delegate, its closure freezes  
> forever and so
> behaves like a local variable and not like a global variable by respect  
> to the
> delegate :
>
> int delegate() getPureFunction(int x){
>     int bar(){
>         return x;
>     }
>     return &bar;
> }
>
> void main(){
>     int delegate() myPureFunction;
>     myPureFunction = getPureFunction(5);
> }
>
> In this example, myPureFunction looks like a pure function, does it?
> So how does dmd 2.022 behave for such kind of "pure delegates" ? Do you  
> think
> there is a futur for pure delegates in the D language ? If not this  
> would mean
> that we cannot use the power of delegates (to do real functionnal  
> programming) and
> the power of purity in the same time, which will be very disapointing for
> programmers, don't you think ?
>

Yes, it was previously discussed many times (not only delegates but any function in general (locally impure)).
Current plan it to make pure function restrictive and then lift unnecessary restrictions where possible.

> This was my first question. The second one concerns purity and parallel
> programming. Is dmd 2.022 implementing some kind of parallelism thanks  
> to pure
> function? In fact I have been argued that "pure" keyword is not enough  
> for the
> compiler to make an efficient parallel program. The problem would be  
> that the
> compiler has no mean to know the granularity of the tasks. What are your  
> feelings
> about that?
>

This is not implemented yet. Pure function are just being added into language.

> Thanks a lot
>
>
>