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Re: [Scheme-reports] Seeking review of sets and hash tables proposals
Alexey Radul scripsit:
> > So far I haven't heard about any *actual* cases of people requiring
> > specialized equivalence predicates, though it's easy to make up
> > hypotheticals.
> How about record types? equal? is not specified to compare their
> contents recursively, so if I want those semantics I have to force
> them with a custom equivalence predicate, and therefore a custom hash
> function. I have written a hash function because of this, so this
> meets your criterion of non-hypotheticalness.
You are the first person to say so.
> How about sets? Suppose I want to use sets as keys in a hash table,
> with set=? as the equivalence predicate?
What's the practical application of sets as keys?
In any case, hash functions for containers are easy to write:
(lambda (elem) (xor (hash elem) acc))
where `hash` is an equality hash function. This is perhaps an argument
for exposing `hash` from SRFI 69.
Note that nobody these days would clamor for fundamental laws John Cowan
of *the theory of kangaroos*, showing why pseudo-kangaroos are cowan@x
physically, logically, metaphysically impossible. http://www.ccil.org/~cowan
Kangaroos are wonderful, but not *that* wonderful. --Dan Dennett on zombies
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