[Haskell-cafe] Re: Specify array or list size?

Chung-chieh Shan ccshan at post.harvard.edu
Sat May 7 17:11:20 EDT 2005

Daniel Carrera <dcarrera at digitaldistribution.com> wrote in article <427D1818.70100 at digitaldistribution.com> in gmane.comp.lang.haskell.cafe:
> feucht at uni-koblenz.de wrote:
> > you may use a tuple?
> Hhhmm... I just tried it. It looks like Hugs doesn't like tuples with 
> more than 5 elements. :-(

You can nest tuples.  And that might be a good idea given that you know
the size of the array, and it's conveniently a power of 2.

data A2 a = A2 !a !a
type A4 a = A2 (A2 a)
type A16 a = A4 (A4 a)
type A256 a = A16 (A16 a)

It's not hard to index or assign into such an "array".  You have a
choice as to what to use as the type of indices into such an "array".
It may be most convenient to use Int, but Word8 prevents out-of-bound
errors, and A2 (A4 Bool) would probably be most elegant. (:

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Science operates according to a law of conservation of difficulty. The simplest
questions have the hardest answers; to get an easier answer, you need to ask
a more complicated question. -- George Musser. Color Madness. Oddball maps can
require more than four colors. Sci. Am., January 2003.

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