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Re: Fundamental design flaws

This page is part of the web mail archives of SRFI 44 from before July 7th, 2015. The new archives for SRFI 44 contain all messages, not just those from before July 7th, 2015.

> >  example rather than BAG-CONTQ?, BAG-CONTV?, BAG-CONTAINS? (and,
> >  perhaps BAG-CONTAINS=? to permit an arbitrary predicate).
> >
> >  For something like a hash table, sure -- at creation time I really
> >  need to establish what notion of equality (and hence, hashing) is in
> >  play -- but for bags?
> OK.  This point I concede.  I don't like the handling of equality
> functions either.  I'd probably prefer optional comparison arguments
> to many of the procedures, but I'd have to talk with Scott and
> Matthias about this before becoming certain that that would be better.

I can see both sides here, but let me state the other side that you may 
not be considering.  There may be bags whose internal representation is 
dependent on the equivalence function in the same way that its important 
for hash table based dictionaries.  A bucket based bag, for example, may 
need the equivalence function to classify the values it stores, allowing 
it to have logarithmic performance for contains? because it has 
pre-sorted its values in a certain way.  This is the rationale for 
pre-specification of the equivalence function.  If all bags were 
completely unorganized collections of values and all had guaranteed O(N) 
lookup times, then it would be just fine to pass the equivalence 
function at call time.


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