[Python-Dev] Anonymous blocks: Thunks or iterators?

[Jim Jewett]

Brian Sabbey:

> It is possible to implement thunks without them creating their own
> frame. They can reuse the frame of the surrounding function ...

> The implementation just needs to take care
> to save and restore members of the frame that get clobbered when the
> thunk is running.

Michael Hudson:

> Woo.  That's cute.

It *sounds* horrendous, but is actually pretty reasonable.

Conceptually, a thunk replaces a suite in the caller.  

Most frame members are intended to be shared, and changes 
should be visible -- so they don't have to (and shouldn't) be restored.

The only members that need special attention are (f_code, f_lasti)
and possibly (f_blockstack, f_iblock).  

(f_code, f_lasti) would need to be replaced with a stack of pairs.
Finishing a code string would mean popping this stack, rather 
than popping the whole frame. 

Since a completed suite leaves the blockstack where it started, 
(f_blockstack, f_iblock) *can* be ignored, though debugging and
CO_MAXBLOCKS both *suggest* replacing the pair with a stack of
pairs.

-jJ