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From: new@ee.udel.edu (Darren New)
Newsgroups: comp.lang.smalltalk
Subject: Re: Please Explain Difference Between $A And 'A'
Message-ID: <49912@nigel.ee.udel.edu>
Date: 5 Apr 91 19:20:40 GMT
References: <40923@cup.portal.com>
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In article <40923@cup.portal.com> Will@cup.portal.com (Will E Estes) writes:
>In learning Smalltalk, I am finding cases where semantically identical, 
>but logically distinct, object types do not get treated the same.  One
>case is point is the difference between single character objects (e.g.,
>$C) and single character string arrays (e.g., 'C').

'C' and $C are clearly not "semantically identical" or you wouldn't be
having this problem, eh? :-)

The problem is the 'C' is a string which happens to be one character long
and $C is a single character.  (The distinction is there in most lower-
level languages, too.)  Would you want '3' = 3 to work?  How 
about '18.2' = 18.2 or '3/4' = 0.75 ?  

>1) Is this example evidence of bad implementation on Digitalk's part,
>or is this considered good Smalltalk style?  In other words, should
>it be a goal in writing Smalltalk methods to make semantically identical
>things work together.  Or does good Smalltalk live by the "separate,
>but equal" rule?

See above.  Where do you stop?  It's good Smalltalk.  That's why it is
possible to redefine equality operators on a class-by-class basis.

Try ('C' at: 1) < $C or something like that. Maybe $C asString < 'C'.
Depends on exactly what conversions your particular image includes.

>2) Are there many other instances of this sort of thing in Smalltalk?
>Maybe someone could review the most common gotchas....

Lots of them.  You'll find them.
                       -- Darren
-- 
--- Darren New --- Grad Student --- CIS --- Univ. of Delaware ---
----- Network Protocols, Graphics, Programming Languages, FDTs -----
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