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From: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Newsgroups: comp.lang.c
Subject: Re: goto's and switch statements -- mild proposal
Message-ID: <997@bsu-cs.UUCP>
Date: Wed, 31-Dec-69 18:59:59 EDT
Article-I.D.: bsu-cs.997
Posted: Wed Dec 31 18:59:59 1969
Date-Received: Sat, 22-Aug-87 04:18:39 EDT
References: <855@tjalk.cs.vu.nl> <2683@hoptoad.uucp> <916@haddock.ISC.COM> <298@auvax.UUCP> <10265@orchid.waterloo.edu> <6289@brl-smoke.ARPA>
Reply-To: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Organization: CS Dept, Ball St U, Muncie, Indiana
Lines: 47
Summary: treat characters as integers

In article <6289@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) 
writes (about "case 'a' :: 'z' :" and similar ranges in case statements):
      There's another serious problem underlying all these suggestions;
      namely, that "a through z" has a well-defined meaning [especially
      in an international setting].  The only well-defined ordering I
      think could be used meaningfully in a standard would have to be
      the native run-time collating sequence based on fixed-size letter
      units.

It seems simplest to me to stay with the character-is-integer paradigm
and treat each constant used to specify the range as an integer.  (I
note that K&R specifically say on page 202 that the 'constant-
expression' in a switch statement must be int.)  One thing I expect to
always be true for C, even as it evolves to accomodate different
character sets, is that each distinct character constant will
correspond to a distinct int value.  Otherwise a lot of code would
break badly, not to mention K&R's entire book.

Then the range is always well-defined, except that the compiler would
warn about empty ranges.  Also, the compiler would probably need to
warn about overlapping ranges.

Much of the time, when a range like this is used in a switch statement,
the user is thinking of a fast jump table implementation rather than an
if-then-else.  It's up to the user to make sure this makes sense, even
if the character set has holes.

Here's an aside not directed at anybody in particuler.

I think that for too long language designers have tried to accomodate
the vagaries of EBCDIC, specifically, that it's a character set with
holes.  Must every language accomodate every whim and fancy of every
badly-designed architecture?  The answer ought to be a resounding no.
The general principle is quite simple:  Those who choose to use
badly-designed machines should have to bear the burden of doing so
without dragging the rest of us down with them.

The six-character limit on external names (I hope it's gone from the
draft now) is another example of not applying this philosophy.  Why
does it make any sense for the rest of the world have to suffer from
the limitations of old linkers on old machines from the sixties?

We should certainly make an effort to accomodate all widely-used
architectures, but not at the expense of seriously distorting the
language for everybody else.
-- 
Rahul Dhesi         UUCP:  {ihnp4,seismo}!{iuvax,pur-ee}!bsu-cs!dhesi