From: Nicholas Milkovits <nmilkovits@...>
Date: 2007-04-02T23:00:14+09:00
Subject: Re: Map Or Collect Redux

Enumerable#select is certainly what I was thinking of.  Certainly
having both collect and map would make it easier for developers coming
from other languages to pick up ruby but often times I see code where
these methods are both used.  Ruby reads very nice and I prefer to use
map just because it semantically makes more sense to me if I am
performing some sort of transformation on the array elements.   (Plus
it is shorter to type : )  ).  When I think of collecting elements I
think of gathering or *selecting* certain elements, collect just does
not seem to imply that the elements will be changed in any way to me.

On 4/2/07, Robert Klemme <shortcutter@googlemail.com> wrote:
> On 02.04.2007 15:17, Nicholas Milkovits wrote:
> > I think the aliases are there for a good syntactic reason.  It seems
> > to me that if you are just filtering out items which meet a certain
> > criteria from one array to be put into a new one (say all elements
> > which are even numbers) then you are collecting.
>
> No, you are actually *selecting*.
>
>  > If you're actually
> > performing a transformation on the elements then you are mapping one
> > array space onto another.
>
> #map and #collect behave identical.  They are just there to make people
> coming from different programming languages feel at home with Ruby faster.
>
> > example
> >
> > arr = [1, 2, 3, 4, 5]
> > arr.collect { |x| if x%2 == 0 then x end }.compact
> > => [2, 4]
> > # Seems like maybe it should be .filter instead of .collect
>
> No, use #select - much more efficient and it does exactly what you are
> trying to accomplish above.
>
> Regards
>
>         robert
>
>
> PS: for the record, I use #map as it is shorter to type and I am laz
>
>