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From: andrew@csd4.csd.uwm.edu (Andy Biewer)
Newsgroups: comp.lang.c
Subject: if ( x && y ) or if ( x ) then if ( y ) ...
Message-ID: <5781@uwm.edu>
Date: 17 Aug 90 02:51:09 GMT
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Reply-To: andrew@csd4.csd.uwm.edu (Andy Biewer)
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Organization: UWM - Computing Services Division
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Much of the time during programming in C I run into the same question about
conditional statements such as the subject.  I have been wondering for quite
some time now about what, if any, differences there are between the two
conditional statements:

  1)  if ( x && y )
          statement;

  2)  if ( x )
          if ( y )
               statement;

It may be a trivial question, however, is there any?  Will `y' in the first
conditional be tested if `x' fails?  I know that it won't in the second.

Because it's a conjunction, logically it is unnecessary to test `y' because
the whole evaluation is false if `x' fails.  And, of course, with a
disjunction it would be necessary to test `y'.  But, is the compiler smart
enough to take these facts into consideration (or is it even possible to)?

Andy B.