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From: ralph@CS.ARIZONA.EDU ("Ralph Griswold")
Newsgroups: comp.lang.icon
Subject: Re:  Uses of dynamic typing
Message-ID: <9011171336.AA22105@cheltenham.cs.arizona.edu>
Date: 17 Nov 90 13:36:15 GMT
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I disagree with your characterization of types and variables in Icon. It's not
that a variable doesn't have a type until an assignment is made to it, but
rather that variables are not typed, but values are. Note that every variable
has the null value initially.

I realize this distinction may seem a bit strange to persons who are used
to languages like Pascal, but if you look at the implementation of Icon,
you'll see that's exactly what's going on.  A variable is simply a place
to store a value, all variables are the same size, as are all values.  All
values carry an identifying type.

As to the usefulness of non-types variables, in my experience, it's mostly
in heterogeneous structures. The elements of a list, for example, are
variables. They can have different types in the same list. Heterogeneous
structures occur frequently in Icon programs. I believe the second edition
of the Icon Programming Language points out examples.

  Ralph Griswold / Dept of Computer Science / Univ of Arizona / Tucson, AZ 85721
  +1 602 621 6609   ralph@cs.arizona.edu  uunet!arizona!ralph