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From: jackson@jabberwock.shs.ohio-state.edu (Michel Jackson)
Newsgroups: comp.lang.c
Subject: Re: New super switch, was Re: The final word on GOTO
Summary: switch/case/default dangerous to health
Keywords: switch case cases goto
Message-ID: <180@jabberwock.shs.ohio-state.edu>
Date: 9 Oct 89 01:43:39 GMT
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Reply-To: Michel Jackson <jackson@cis.ohio-state.edu>
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Organization: The Ohio State University, Division of Speech and Hearing Science
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Press, Flannery, Teukolsky, & Vetterling remark, in their very useful
book _Numerical Recipes: The Art of Scientific Computing_

  Every programming language has some number of "goodies" that the
  designer just couldn't resist throwing in ... In FORTRAN we consider the
  ill-advised control structures to be
    -assigned GOTO and ASSIGN statements
    - computed GOTO statement
    - arithmetic IF statemetn
  In Pascal an example is
    -CASE ... OF

In the companion volume, _Numerical Recipes in C_ (yes, i have & use
both ...), they remark

  In C, the most dubious control structure is the switch...case...default
  construction, recognizable to FORTRAN programmers as a kind of elaborate
  "computed goto". Not only is the structure a confusing one, with a
  bizarre "drop through" feature, it is also burdened with uncertainty,
  from compiler to compiler, about what data types are allowed in its
  control expression. It can virtually always be easily replaced by a
  more recognizable and translatable if ...else construction. (p.13)

I generally agree with them. Some of the most confusing code I have
ever written relied on (long) switch statements and various drop
throughs (exhaustive testing of a function that had some 8-10
arguments & needed to be demonstrated correct & also had to be shown
to handle various combinations of incorrect inputs properly) ... i
eventually gave up trying to debug my own code & rewrote it from scratch
with a pile of if's. Surely adding "cases" will make switch statements
even harder to figure out ...

i must admit, though, that "tame" switch statements are a great convenience.
	---michel jackson