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From: gudeman@cs.arizona.edu (David Gudeman)
Newsgroups: comp.lang.functional
Subject: Re: A question about types in ML
Message-ID: <27613@megaron.cs.arizona.edu>
Date: 17 Nov 90 17:56:31 GMT
Organization: U of Arizona CS Dept, Tucson
Lines: 20

In article  <2235@opal.cs.tu-berlin.de> Wolfgang Grieskamp writes:
]
]If a functions semantic maps D->D, then the rare case 
]is that it maps also D/bottom->D/bottom. In fact i have problems 
]to imagine meaningful functions except identity which behave like this. 

I'm not sure I understand this.  It sounds like you are talking about
functions that are strict in bottom (that is, if they are given bottom
as an argument, they produce bottom as a result).  If so, then there
are hoards of natural functions that meet this criteria.  Most
arithmetic functions for example.  In fact, this case is so common
that some languages have only _one_ builtin function that is not
strict (if-then-else).  And many languages do not allow the programmer
to define new non-strict functions, since they evaluate the arguments
before they call the function.
-- 
					David Gudeman
Department of Computer Science
The University of Arizona        gudeman@cs.arizona.edu
Tucson, AZ 85721                 noao!arizona!gudeman