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From: gudeman@cs.arizona.edu (David Gudeman)
Newsgroups: comp.lang.misc
Subject: Re: Dynamic typing -- To Have and Have Not
Message-ID: <628@optima.cs.arizona.edu>
Date: 14 Mar 91 10:41:45 GMT
Sender: news@cs.arizona.edu
Lines: 36

In article  <1991Mar13.195039.22587@mathrt0.math.chalmers.se> Lennart Augustsson writes:
]In article <614@optima.cs.arizona.edu> gudeman@cs.arizona.edu (David Gudeman) writes:
]I don't agree.  I think that a lot of people who prefer dynamically
]typed languages are ignorant of the alternatives.  

I doubt there are many people who are only experienced with
dynamically typed languages.  If you are refering to type inference as
the alternative, you may be right -- people who prefer dynamically
typed languages may tend to be unaware of it (like everyone else), but
I doubt they would like it, ignoring efficiency issues and sticking
strictly to expressiveness and program reliability.  When worried
about efficiency, everyone prefers statically typed languages, I never
meant to claim otherwise.

Statically typed languages without declarations are a step in the
right direction, but not far enough for my taste.  You are still too
restricted in the sorts of expressions you are allowed to write (not
to mention that for non-toy languages, compilation is slow as a
beejeeber).  But at least it solves the problems of errors in
declarations and having to make pervasive changes to the code when you
change declarations.

]  tree_insert Null         x         = Node x Null Null
]  tree_insert (Node y l r) x | x < y = Node (tree_insert l x) r
]  tree_insert (Node y l r) x         = Node l (tree_insert r x)
]The compiler infers the type (i.e. you don't have to write it!)
]  tree_insert :: (Ord a) => Tree a -> a -> Tree a
]which means that tree_insert will work on any type of data that is a
]member of class Ord (i.e. has < defined).

Can you use this function to insert different types in the same tree?
If so, how is it different from dynamic typing?
--
					David Gudeman
gudeman@cs.arizona.edu
noao!arizona!gudeman