[pypy-dev] hash negotiation

Armin Rigo arigo at tunes.org
Mon Mar 3 17:43:59 CET 2003

Hello Christian,

More about Laura's comments in a next e-mail.  Just a couple of pragmatic 

On Sat, Mar 01, 2003 at 08:01:18PM +0100, Christian Tismer wrote:
> It may negotiable whether we want to preserve an extra flag
> in all the hashable objects whether the hash has been computed,
> or repeat CPython's way to preserve a single value for this.

This abuse of -1 was for error passing, and we don't need it, so I thought it 
should just go away. My point of view is definitely that any "C hack" should 
go away.

For objects like strings that internally use -1 for yet another usage ("not 
computed yet"), our W_StringObjects are free to repeat that and never actually 
return a value of -1. That's fine.

Regarding CPython compatibility, that can be added later if needed by keeping 
an explicit track of this kind of changes (hence the XXX in my comments -- but 
we certainly need a better way to sort this kind of comments). It might be as 
simple as calling our own hash functions, and then, if that returns -1, 
translate it into -2 (as this is how all CPython objects work around this 
special value).

Well, again the best solution is probably to have a doc repository for this 
kind of issues.

A bientot,


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