Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!elroy.jpl.nasa.gov!usc!zaphod.mps.ohio-state.edu!tut.cis.ohio-state.edu!ucbvax!SOPHIST.UCHICAGO.EDU!goer
From: goer@SOPHIST.UCHICAGO.EDU (Richard Goerwitz)
Newsgroups: comp.lang.icon
Subject: type coercion
Message-ID: <9004111306.AA07853@sophist.uchicago.edu>
Date: 11 Apr 90 13:06:19 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: inet
Organization: The Internet
Lines: 35

Consider the following:

   Static type checking is not realistically possible for a language
   such as Icon. Consider the expression:

	if x=0 then "small" else 1

   The type of this expression may be impossible to determine until
   run time.  In Icon as well as such expressions as these it is
   possible to check the type of a value at run time and act according
   to this information.  I have used this myself to obtain the
   behaviour of variant types.  For example:

	if type(x)=="integer" then x+1 else 0 

   Expressions such as this are quite foreign to languages with static
   type checking.  Perhaps what you need is some kind of "lint"
   program like that which the C programming language has.  For
   programs which can be statically typed it could warn of any type
   clashes and coercions that will occur, for other programs it could
   just indicate that static type checking was not feasible.

I don't disagree that expressions such as this are foreign to languages
with static type checking.  What I wonder is whether a thing like optional
static typing might be applied to variables, and not expressions.  In
this scenario,

	if x = 0 then "small" else 1

would be fine.

Just curious.

    -Richard L. Goerwitz              goer%sophist@uchicago.bitnet
    goer@sophist.uchicago.edu         rutgers!oddjob!gide!sophist!goer