>>>>> "R" == Ruud <[email protected]> writes:
R> On 2011-01-11 11:44, Uri Guttman wrote:
>> these are equivilent:
>>
>> my @out = grep /foo/, @in ;
>> my @out = map { /foo/ ? $_ : () } @in ;
R> Indeed equivalent. There is a difference though
R> in what comes out of map and grep:
R> perl -wle'
R> my @in = 1 .. 4;
R> print "@in";
R> ++$_ for map { $_ % 2 ? $_ : () } @in; # copies
R> print "@in";
R> ++$_ for grep { $_ % 2 } @in; # aliases
R> print "@in";
R> '
R> 1 2 3 4
R> 1 2 3 4
R> 2 2 4 4
interesting and evil. my rule is grep/map should never do side effects
and do read only work. if you want modifications use a proper loop.
uri
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