[e-lang] Looser memoization and constant-folding: will this work?

[Kevin Reid]

On May 6, 2006, at 12:50, Mark S. Miller wrote:

> Kevin Reid wrote:
>>    - Is this correct?
>
> I think so.

So far, testing agrees.

>>    - Is there a way to handle the DeepFrozen-returns-DeepFrozen case
>> which does not involve two possibly-arbitrarily-expensive  
>> evaluations?
>
...
>        # map from msgs to good results
>        def cache := [].asMap().diverge()
>        # map from msgs to either null or [possible result]
>        def dfCache := [].asMap().diverge()
...
>                    if (dfCache[msg] =~ [oldResult]) {
>                      if (df == oldResult) {
>                        # Happened again, so memoize it for real
>                        cache[msg] := df
...

Clever. Unfortunately, it won't work for constant folding since a  
definite answer is needed the first time a particular call is seen.

I'll certainly try it for the memoizer, however.

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>