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Re: Efficiency of map vs. more verbose basic/fundamental code

by eyepopslikeamosquito (Chancellor)
on Oct 04, 2012 at 22:47 UTC ( #997338=note: print w/replies, xml ) Need Help??

in reply to Efficiency of map vs. more verbose basic/fundamental code

The later edition of Effective Perl Programming has item 20, "Use foreach, map and grep as appropriate", which gives an excellent summary of when to use foreach, map and grep:

  • Use foreach to iterate read-only over each element of a list
  • Use map to create a list based on the contents of another list
  • Use foreach to modify elements of a list
  • Use grep to select elements in a list

Hall, McAdams and foy further caution against modifying a list via map:

"For efficiency, $_ is actually an alias for the current element in the iteration. If you modify $_ within the transform expression of a map, you modify the input data. This is generally considered to be bad style, and -- who knows? -- you may even wind up confusing yourself this way. If you want to modify the contents of a list, use foreach."

I'm pretty sure the earlier edition you are reading has a similar item. If you read this item, you should not be confused about which one to use. I suggest you focus on clarity and only bother benchmarking if performance is really critical.

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[Mj1234]: Hello Monks, I have installed Active perl 5.16 and 5.14 but I dont find Devel::GDB package when I try to install through ppm
[Discipulus]: i'v installed ubuntu 16.04lts and i'm quite disappointed: is deadly simmilar to new win osses where you cannot find even simple things...
[Corion]: Hi Discipulus ;)
[Corion]: Mj1234: Maybe Ubuntu didn't package Devel::GDB? In that case, consider using local::lib and install the module from CPAN
[Corion]: But a quick Google search turns up this page, which seems to suggest that it should be packaged
[Discipulus]: iirc active perl has repositories only for last 2 o 3 major release of perl Mj1234. I strongly suggest portable version of strawberry perl and use cpan client to install modules
[choroba]: Also, who needs GDB when there's hdb?

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