Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!samsung!uunet!ogicse!unmvax!bbx!bbxsda!scott
From: scott@bbxsda.UUCP (Scott Amspoker)
Newsgroups: comp.std.c++
Subject: Re: case()
Keywords: case statement
Message-ID: <962@bbxsda.UUCP>
Date: 13 Aug 90 20:26:17 GMT
References: <26842@pasteur.Berkeley.EDU> <26857@pasteur.Berkeley.EDU> <56515@microsoft.UUCP>
Reply-To: scott@bbxsda.UUCP (Scott Amspoker)
Organization: Basis International,  Albuquerque, NM
Lines: 38

In article <56515@microsoft.UUCP> bobatk@microsoft.UUCP (Bob ATKINSON) writes:
>In article <26857@pasteur.Berkeley.EDU> bilmes@icsib (Jeff Bilmes) writes:
>>This does not warrant
>>extending the language when you can do the semantic equivalent as
>>easily as:
>>
>>    if (exp == val1) 
>>	s1 
>>    else if (exp == val2)
>>	s2
>>    else if (exp == val3 || exp == val4 || exp == val5 || ...)
>>	s3
>>    ...
>
>By this logic, switch statements should not have been invented
>in the first place.  Clearly in C a need was felt for this syntactic
>sugar....

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.

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!

It is difficult to expand the multiway-jump concept to include
non-integral values.  In those cases, a switch statement really is
nothing more than a series of 'if's.

-- 
Scott Amspoker
Basis International, Albuquerque, NM
(505) 345-5232
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