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From: karl@grebyn.com (Karl Nyberg)
Newsgroups: comp.lang.ada
Subject: Re: Question about Ada expressions
Message-ID: <8910122337.AA06188@grebyn.com>
Date: 12 Oct 89 23:37:42 GMT
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List-Id: <comp.lang.ada>

I had a friend call yesterday after spending five hours trying to figure out
why some C code didn't work based on this expression:

	if (variable & MASK == VALUE)

He mistook the rules of precedence, just as Robert Firth expressed it in his
response.  The K&R book explains this reasoning:

	Note that the precedence of the bitwise logical operators &, ^ and |
	falls below == (test for equality) and !=  (test for inequality).
	This implies that bit-testing expressions like

		if ((x & MASK) == 0) ...

	must be fully parenthesized to give proper results.  [p. 49]

Seems like it was kind of the Ada designers to preclude this from the
language.  Getting an error during compile time would have saved my friend
immense difficulty.  Getting a manual might have helped him, too...

-- Karl --