map{} is a wrong idea if the output isn't being used. That is why it can be "slow". But I am hearing that there is no performance penalty for a "void map{}"... meaning that Perl won't create and allocate memory for the output of map{} if is not being used? I didn't know about that. When did this performance enhancement happen?

I think we both agree that a "void map{}" is bad style. I looked at the post from Ratazong and saw the following code being bench marked: 

my @sqrt_results = map { sqrt ($_ ) } @input;

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This is a perfect thing for map{}: translate one thing to another. map{} can also make 1 to many and many to one translations. In general, I use map{} when the transformation can be expressed as a "one liner+" and foreach() when the code is longer. As a matter of style, this allows me to put foreach(@input) at the top instead of at the end of the program text, compare with: @output = map{lots of lines}@input.

In reply to Re^3: Map Vs Foreach by Marshall
in thread Map Vs Foreach by perlCrazy

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