Re^5: map versus for

I think I get it: Why use a gun to kill a cockroach when you have a perfectly good shoe. Since you don't get the benefits of mapping the data, and as such you are wasting time and space, it's better that you use "for".

So, if I am understanding you correctly,

for: used for iterating an action over a series of items.

map: used when one needs to create create a table of data which will be used at a future time.

-Actualize

Comment on Re^5: map versus for

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Re^6: map versus for by blazar (Canon) on Aug 05, 2008 at 22:07 UTC
map: used when one needs to create create a table of data which will be used at a future time. I personally believe that you nearly got it: more precisely, map is used whenever you clearly have an input list that you want to be (functionally) transformed in an output list. In some sense your reference to the "future time" is correct even if this future may be just as close to the `map()` itself as in "being in the very same statement." At the same time, you can also set side effects within the `map()` block (both to some "external" variables and to the elements of the input list themselves) but you generally don't want to do that. It just... doesnt' smell like that: `C:\temp>perl -E "@a=1..3; @b=map 2($_=2) => @a; say qq\|A = [@a], B = + [@b]\|" A = [2 4 6], B = [4 8 12]` [download] `--` If you can't understand the incipit, then please check the IPB Campaign.	[reply] [d/l] [select]

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Re^6: map versus for
by blazar (Canon) on Aug 05, 2008 at 22:07 UTC

map: used when one needs to create create a table of data which will be used at a future time.

I personally believe that you nearly got it: more precisely, map is used whenever you clearly have an input list that you want to be (functionally) transformed in an output list. In some sense your reference to the "future time" is correct even if this future may be just as close to the map() itself as in "being in the very same statement." At the same time, you can also set side effects within the map() block (both to some "external" variables and to the elements of the input list themselves) but you generally don't want to do that. It just... doesnt' smell like that:

C:\temp>perl -E "@a=1..3; @b=map 2*($_*=2) => @a; say qq|A = [@a], B =
+ [@b]|"
A = [2 4 6], B = [4 8 12]
[download]

--
If you can't understand the incipit, then please check the IPB Campaign.

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