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From: nowlin@iwtqg.att.com
Newsgroups: comp.lang.icon
Subject: Re: Uses of dynamic typing
Message-ID: <9011172202.AA14204@megaron.cs.arizona.edu>
Date: 17 Nov 90 21:39:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: inet
Organization: The Internet
Lines: 35

> than just prove something?

I have three specific examples.  The first is the use of the types "null"
and "file" in programs that can read input from files or from standard
input.  The same expressions can be used for input if the variable used as
a file is set to &null when reading from standard input.  I've used this
many times.  The same kind of scheme can be used for output.

The second example is a set of procedures that does regular expression
matching.  It uses a list of records.  Each record contains a pair of
values; a procedure and an argument to be passed to the procedure.
Sometimes the argument is a string, sometimes it's a cset, and sometimes
it's &null.  Icon doesn't care which I store as the second value in the
record.

The third use is a set of procedures I wrote for a friend.  These
procedures allow a series of global variables to be dumped into a file.  A
complementary set of procedures can read the dump file and reconstruct the
global variables with the same values as the program that dumped them.
These procedures are used to chain together a series of programs.  This
would require a whole series of different variables if Icon didn't allow me
to use the same variable over and over with different types each time.
Very handy.

As a side note we've just recently achieved a breakthrough at work (AT&T)
and we're now allowed to use Icon for "real" projects.  It's great.  Our
methodology calls for code inspections and those of us who are familiar
with Icon initially thought Icon would be much easier to code inspect than
C++ or C.  WRONGO!  The tie in to this subject is that dynamic typing may
contribute to the problem.  It just seems counter intuitive that Icon would
be harder to inspect but after our initial session that was definitely my
impression.  I'll try to figure out why on my own but if anyone has any
ideas throw them out.

Jerry Nowlin (iwtqg!nowlin)