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From: gudeman@cs.arizona.edu (David Gudeman)
Newsgroups: comp.lang.misc
Subject: Re: Dynamic typing (part 3)
Message-ID: <2047@optima.cs.arizona.edu>
Date: 17 Apr 91 17:47:52 GMT
Sender: news@cs.arizona.edu
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In article  <29352@dime.cs.umass.edu> victor yodaiken writes:
]... I do not
]buy the argument that there is a real plus in being able to write
]expressions that may not have any meaning.

If you can't write an expression that may not have any meaning then
your language is not expressive enough to write programs in.

] That is, if I write
]$f(X)$ I should be able to ensure, during design time, that 
]f is defined over all possible instantiations of X. Why, one would
]find it reasonable to do otherwise is beyond me.

That is impossible in a Turing-complete language.  All you can do is
make an arbitrary approximation to that kind of safety.  And static
typing approximations (ones that allow the representation of all
values to be decided at compile time) are overly restrictive for the
amount of safety they provide.  The fact that they are overly
restrictive is easy to see by how much effort is put into getting
around the restrictions.
--
					David Gudeman
gudeman@cs.arizona.edu
noao!arizona!gudeman