Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!gatech!hubcap!ncrcae!ncrlnk!uunet!auspex!guy
From: guy@auspex.UUCP (Guy Harris)
Newsgroups: comp.lang.c++
Subject: Re: Improved switch statement (was Re: goodbye cpp ???)
Message-ID: <744@auspex.UUCP>
Date: 17 Dec 88 21:14:15 GMT
References: <6590072@hplsla.HP.COM> <1106@etive.ed.ac.uk> <33528@bbn.COM> <1907@ogccse.ogc.edu> <574@redsox.UUCP> <14104@oberon.USC.EDU>
Reply-To: guy@auspex.UUCP (Guy Harris)
Distribution: na
Organization: Auspex Systems, Santa Clara
Lines: 24

>This is useful only as syntactic sugar:  the switch statement 
>in C/C++ does *not* compile into a series of
>
>if (expr == case1) ... else if (expr == case2) ...
>
>statements, as your suggestion implies.  Instead, (in all the
>implementations I've seen, anyway)

Sorry, I've seen C implementations where the compiler chooses one of:

	1) an "if" chain

	2) a vectored jump

	3) a table lookup with a vectored jump

depending on the number of cases.  One such implementation is PCC, upon
which a boatload of UNIX C compilers are based.

>The switch statement you suggest would (of necessity) compile into a bunch
>of if()s, which is not really what switch was designed to do...

"switch" was designed to switch among a set of several alternatives; if
that can only be done by an "if" chain, well, that's life....