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From: Georg Bauhaus <sb463ba@l1-hrz.uni-duisburg.de>
Newsgroups: comp.lang.ada
Subject: Re: Formal and informal type systems?
Date: Wed, 29 Sep 2004 01:23:02 +0000 (UTC)
Organization: GMUGHDU
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Date: 2004-09-29T01:23:02+00:00
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Stephen Leake <stephen_leake@acm.org> wrote:
: You [Mark] mention "pattern matching", but I have no clue what dataspace you
: are matching against.

If I may step in, matching is done against a type's values or a type's
constructor functions. A simple example matches integers
against 0, 1, and n:

fun even 0 = true
  | even 1 = false
  | even n = not (even (n - 1))
and odd n = not (even n);

In a call,

even 17;

the argument value 17 is matched against 0, 1, and n in that order.
n wins, resulting in another expression, not (even 16), and so on.


-- Georg