Explicit TCE

[bearophile]

Tyler Jameson Little:

> D could use something like Newsqueak's become keyword. If 
> you're not familial with Newsqueak, become is just like a 
> return, except it replaces the stack frame with the function 
> that it calls.

Are you talking about CPS?
http://en.wikipedia.org/wiki/Continuation_passing_style


> DMD should optimize this already, but explicitly stating become 
> is a key to the compiler that the user wants this call to be 
> eliminated.  Then, more interesting things can be implemented 
> more simply, like a state machine:
>
>     void stateA() {
>         become stateB();
>     }
>
>     void stateB() {
>         become stateC();
>     }
>
>     void stateC() {
>         return;
>     }
>
>     void main() {
>         become stateA();
>     }

Seems nice.


> I'm not sure how D handles stack sizes, so this may be an issue 
> as well if stack sizes are determined at runtime.

D doesn't currently support C99 VLAs, but it supports alloca(), 
so stack frames are sized dynamically. But maybe this is not a 
big problem for CPS.

Bye,
bearophile