[m-dev.] for review: use bitsets in quantification

[Fergus Henderson]

On 07-Nov-2000, Ralph Becket <rbeck at microsoft.com> wrote:
> What we seem to be angling towards is something like Okasaki's
> typeclass with reversible hashing, with the further constraint
> that the hashes must form a contiguous set.

Ah, I never thought of it that way.

`reversible_hash' is certainly a much better mnemonic than the
`convertable_to_int' name that I suggested for the non-contiguous
version.  It immediately suggests a use...

Does Okasaki make much use of this type class?

> So we include (at least) to_int/1, from_int/1, first/0, last/0.
> I think pred/1 and succ/1 should also go in there as methods
> rather than utility functions since they may be more economically
> implemented than
> 	pred(X) = from_int(to_int(X) - 1)
> 	succ(X) = from_int(to_int(X) + 1)

Could you give an example of a more economic implementation?

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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