Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!ll-xn!ames!amdcad!rpw3
From: rpw3@amdcad.AMD.COM (Rob Warnock)
Newsgroups: comp.lang.c
Subject: Re: goto's
Message-ID: <17753@amdcad.AMD.COM>
Date: Wed, 29-Jul-87 21:27:28 EDT
Article-I.D.: amdcad.17753
Posted: Wed Jul 29 21:27:28 1987
Date-Received: Sat, 1-Aug-87 01:41:42 EDT
References: <3289@bigburd.PRC.Unisys.COM> <7571@beta.UUCP>
Reply-To: rpw3@amdcad.UUCP (Rob Warnock)
Organization: [Consultant] San Mateo, CA
Lines: 37

In article <1217@bloom-beacon.MIT.EDU> tdavis@ATHENA.MIT.EDU (Timothy L. Davis)
writes:
+---------------
| In article <465@bms-at.UUCP> stuart@bms-at.UUCP (Stuart D. Gathman) writes:
| >Knuth has an excellent method for converting any program, no matter how
| >convoluted, to perfectly structured code with no goto's.
| I am just finishing a modification of a program which used this precise
| system for "computed" gotos.  What a mess!  It was nearly impossible to read 
+---------------

This is *precisely* what led Bill Wulf (over a decade ago) to publish ago a
short note in ACM SIGPLAN(?) entitled "Global Variable Considered Harmful"
(following Dijkstra's earlier paper "Goto Considered Harmful").

It is not the "goto" per se which is harmful, but the spagetti control
flow which results from an undisciplined use of it, and the resulting human
difficulty in proving that all possible combinations of that control flow
yield the correct results.  (Also see Miller's classic "The Magical Number
Seven Plus Or Minus Two".)

Remember, Dijkstra's definition of "structured programming" was *not* a
simplistic "no gotos", but rather an unceasing vigilence against all manner
of "complexity generators".  Global variables (*all* global variables) create
the same potential for unbridled complexity.

On the other hand, while "no gotos" and "no global variables" are very
useful heuristics, following them doesn't guarantee success.  Murphy's
Something-Or-Otherth Law: "It ain't that simple."


Rob Warnock
Systems Architecture Consultant

UUCP:	  {amdcad,fortune,sun,attmail}!redwood!rpw3
ATTmail:  !rpw3
DDD:	  (415)572-2607
USPS:	  627 26th Ave, San Mateo, CA  94403