Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!snorkelwacker!ai-lab!rpk
From: rpk@wheaties.ai.mit.edu (Robert Krajewski)
Newsgroups: comp.std.c++
Subject: Re: case()
Summary: switch is a laggard compared to the rest of C++
Keywords: case statement
Message-ID: <9907@rice-chex.ai.mit.edu>
Date: 15 Aug 90 01:10:10 GMT
References: <26842@pasteur.Berkeley.EDU> <26857@pasteur.Berkeley.EDU> <56515@microsoft.UUCP> <962@bbxsda.UUCP>
Reply-To: rpk@rice-chex.ai.mit.edu (Robert Krajewski)
Organization: MIT Artificial Intelligence Laboratory
Lines: 25

In article <962@bbxsda.UUCP> scott@bbxsda.UUCP (Scott Amspoker) writes:
>I disagree.  A series of 'if' statements implies a sequence of tests
>to be performed.  A 'switch' implies a multi-way branch in which any
>of the possible case values are equally likely to occur.  This can
>be easily optimized by a compiler.  Although the standard does not 
>mandate it, a switch statement is expected, in most cases, to be 
>implemented as a quick indirect-jump table.

Let the compiler decide that, then. switch should just specify
semantics.

>It is not unusual to have switches with over 100 cases which would
>not perform acceptably as a series of 'if' statements.  Syntactical
>sugar indeed!

Well, there is one other benefit to switch: the switched thing is
an expression, it is evaluated only once, right ?  So you get a
temporary for free if you need it.

I would like to see switch be extended at least to cover data types
for which == holds.  It's unfortunate that case tags have to be constants,
but I can live with that.
-- 
Robert P. Krajewski
Internet: rpk@ai.mit.edu ; Lotus: robert_krajewski.lotus@crd.dnet.lotus.com