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Re: predicate->char-set considered harmful

This page is part of the web mail archives of SRFI 14 from before July 7th, 2015. The new archives for SRFI 14 contain all messages, not just those from before July 7th, 2015.

>    From: lucier@xxxxxxxxxxxxxxx
>    Date: Sun, 17 Dec 2000 22:44:02 -0500 (EST)
>    What about predicate->char-set on large (Unicode or larger) character sets?
>    I'd certainly not want to call a function 65536 times (or 2^32 times) just
>    to construct a char-set. And a user may not know that a Scheme
>    implementation has two-byte or four-byte characters. (How many people know
>    that Gambit has 2-byte chars by default?) I just don't see how it's really
>    helpful to have this function, and I think it should be eliminated.
> Valid concerns, but it can't be helped. People frequently describe sets of
> things by predicate; you need a way to convert that into a true set.

There are enough ways to build char-sets that I don't think it
is *essential* that one has such an expensive operation.  For example,
I think it would be better to just construct a list of chars, and use

I hope you don't try to define predicate->bitset in a later SRFI ;-).