From: Mark Van Holstyn <mvette13@...>
Date: 2006-04-13T10:04:21+09:00
Subject: Re: map_if, collect_if ???

------=_Part_12126_19317626.1144890257913
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

Try using the 'select' method...

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




On 4/12/06, Bruce Woodward <bruce.woodward@gmail.com> wrote:
>
> Hi,
>
> I have been through the pickaxe book, looking at the array and enumerable
> built-in class and module and can't find a way of achieving a map_if or
> collect_if.
> From pickaxe, collect "Returns a new array containing the results of
> running
> block once for every element in enum". Of course map is an alias to
> collect.
> There is find_all but it returns an array containing the elements of enum=
,
> not the results of running the block, so I have written one.
> Is there a better way that already exists?
> thanks,
> Bruce.
>
> module Enumerable
>
>   # returns an array containing the results of running block once for
> every
> element in enum, for which block
>   # is not false.
>   def map_if
>     rt, r =3D [], nil
>     self.each { |e| (r =3D yield(e)) and rt << r }
>     rt
>   end
>   alias :collect_if :map_if
>
> end
>
> a =3D [ 1,2,3,4,5 ]
>
> b =3D a.map_if { |i|
>   (i % 2 !=3D 0) and (i * 10)
> }
>
> p b ##  [10, 30, 50]
>
>


--
Mark Van Holstyn
mvette13@gmail.com
http://lotswholetime.com

------=_Part_12126_19317626.1144890257913--