in reply to Re: Re: When would you choose foreach instead of map?
in thread When would you choose foreach instead of map?

I thought map() was optimized for use in void context. I'd never use map() in such a case in this as for() is much more elegant (all IMO of course). Can you explain why the map() version takes up so much memory?

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Re: Re^3: When would you choose foreach instead of map?
by BrowserUk (Patriarch) on May 21, 2004 at 10:28 UTC

    I believe* that the reason is nothing to do with the void context. for is optimised to treat the range operator as an iterator, by which I mean it doesn't generate a list of 1_000_000 scalars, it simply supplies the next incremented value as $_ for each iteration.

    map on the other hand doesn't have this optimisation and so a very large list is generated as the input to map. This is what (briefly) consumes the memory. For short ranges this isn't a problem, but for larger ones, it's worth avoiding.

    * I'm fairly confident that this is the case, but it is acquired knowledge rather than something I can point my finger at the sources and say "There".

    Examine what is said, not who speaks.
    "Efficiency is intelligent laziness." -David Dunham
    "Think for yourself!" - Abigail
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