[Melbourne-pm] The || operator
david_dick at iprimus.com.au
Mon Oct 31 15:22:31 PST 2005
Alfie John wrote:
> Hi (),
> Quick question:
> @a = (4,5,6) || (7,8,9);
> use Data::Dumper;
> print Dumper[@a];
> I would have thought @a would have contained (4,5,6). Looking through
> perlop, it says that this is the wrong way to use || and what would
> happen is:
> @a = scalar( (4,5,6) ) || (7,8,9);
> and thus @a would contain 3. But this is wrong too.
> In fact, @a contains (6).
> Any thoughts?
okay. guessing away here... :)
the (7,8,9) array ain't ever going to be reached, cos the || will short
circuit it, so disregarding the (7,8,9) altogether and looking at
perldoc -f scalar
Because "scalar" is unary operator, if you acci
dentally use for EXPR a parenthesized list, this
behaves as a scalar comma expression, evaluating
all but the last element in void context and
returning the final element evaluated in scalar
context. This is seldom what you want.
which would give you 6?
interestingly enuff, when you run the script under warnings, it warns
twice of "Useless use of a constant in void context", which i s'pose
refers to the '4' and '5'.
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