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Re^2: AND OR

by davidrw (Prior)
on May 14, 2006 at 14:19 UTC ( #549320=note: print w/replies, xml ) Need Help??

in reply to Re: AND OR
in thread AND OR

(for keyword or further-search purposes) that behavior is dubbed "short-circuiting"

And i'll toss in a good C example (avoid method calls on undef/null):
int *x; if(ptr != NULL && *ptr==5){ ... } if( objPtr != NULL && objPtr->foo() ){ ... } # extended to perl: my $obj = Foo::Bar->new(); if( $obj && $obj->blah() ){ ... }
Update: added parens for ->foo()

Replies are listed 'Best First'.
Re^3: AND OR (C meth)
by tye (Sage) on May 14, 2006 at 16:29 UTC

    Heh, you hit a C pet peave of mine. This:

    if( objPtr != NULL && objPtr->foo ){ ... }

    doesn't actually call any methods. You need objPtr->foo() for that. And the ANSI C committee should have made the "&" for getting a pointer to a method mandatory instead of optional and discouraged, as needing to do that is relatively rare, rarer than the mistake of not realizing that C requires the parens unlike several other quite similar languages. Further, this particular mistake usually results in compiler output that is quite difficult to diagnose, IME.

    - tye        

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