Path: utzoo!utgpu!watmath!clyde!att!ihlpb!nevin1
From: nevin1@ihlpb.ATT.COM (Liber)
Newsgroups: comp.lang.misc
Subject: Re: Expression Based Language
Message-ID: <9310@ihlpb.ATT.COM>
Date: 30 Dec 88 22:20:49 GMT
References: <3300001@uxg.cso.uiuc.edu> <3290002@hpctdls.HP.COM> <4505@xenna.Encore.COM> <2583@ficc.uu.net>
Reply-To: nevin1@ihlpb.UUCP (55528-Liber,N.J.)
Organization: AT&T Bell Laboratories - Naperville, Illinois
Lines: 37

In article <2583@ficc.uu.net> peter@ficc.uu.net (Peter da Silva) writes:
>In article <4505@xenna.Encore.COM>, pierson@mist (Dan Pierson) writes:

>I once modified a version of the small-C compiler
>to make 'C' a completely expression-based language. The changes are really
>very minor (at least for that case... I don't know quite how full 'C'
>would take it).

This won't work too well in (full) C.  The problem is that pure
expression-based languages (like LISP) tend to be typeless as well.
Having to return a specific data type severely limits the usefulness of making
control-flow constructs (if, switch, for, etc.) expression-oriented.

>> If C was an expression based language, the ?: expression would be
>> totally redundant with a normal if statement (of course it would
>> still be more compact).

That is why the ?: operator is limited to returning values of the same
type (or coersable type), while the if statement is not.

>> This is not fantasy, the equivalent expressions exist and are useful
>> in BLISS and Lisp.

I agree.


Side note:  In LISP, I tend to think of the side-effect of an expression
as what it does, while its main purpose is to return a value (eg: the
side effect of setq is to assign a value to a variable, while its main
effect is to return its value or the variable; I can't remember which).
In Icon, I tend to reverse these definitions.  Is it just me, or is there
something about the different paradigms that switch these definitions?


Happy New Year!
-- 
NEVIN ":-)" LIBER  AT&T Bell Laboratories  nevin1@ihlpb.ATT.COM  (312) 979-4751