Re^2: AND OR


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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 )

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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() ){ ... }
[download]

Update: added parens for ->foo()

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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 ){ ... }
[download]

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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