From: Logan Capaldo <logancapaldo@...>
Date: 2006-04-13T10:18:36+09:00
Subject: Re: map_if, collect_if ???

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On Apr 12, 2006, at 9:04 PM, Mark Van Holstyn wrote:

> Try using the 'select' method...
>
> irb(main):002:0* a = [ 1,2,3,4,5 ]
> irb(main):003:0> b = a.select { |i|
> irb(main):004:1*  (i % 2 != 0) and (i * 10)
> irb(main):005:1> }
> => [1, 3, 5]
>
>

Not the effect he was looking for:

b = a.map_if { |i| (i % 2 != 0) and (i * 10) }
p b
[10, 30, 50]

Personally I think his solution is a little icky, what if you wanted  
to do

if x
   then map false

a.map_if  { |i| (i % 2 != 0) and false }
would break down and you'd get an empty array

I would just do

a.select { |i| (i % 2 != 0) }.map { |i| i * 10 }

if I needed map-if style functionality
  
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