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From: Schauble@MIT-MULTICS.ARPA (Paul Schauble)
Newsgroups: net.lang.c
Subject: SWAP macro
Message-ID: <1577@brl-smoke.ARPA>
Date: Mon, 23-Jun-86 00:25:34 EDT
Article-I.D.: brl-smok.1577
Posted: Mon Jun 23 00:25:34 1986
Date-Received: Tue, 24-Jun-86 05:14:20 EDT
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I've gotten lots of respones to my request for a form of the macro that
would make
  swap(*a++, *b++);
 work.  Almost all of them missed the point.  The swap requires a
temporary.  Generating that temporary requires knowing the type.
Several of the solutions would work fine if *a and *b were int's, but I
never said that.

Recall the my original message was posted as a justification for a
typeof macro, akin to sizeof.  I find that the need to generate
temporaries in a macro is not uncommon.  Unless one is willing to do a
different version of the macro for each type, you need a way to generate
a new variable of the same type as one of the macro args.  The language
provides no way to do this.