From: Robert Klemme <bob.news@...>
Date: 2005-07-11T20:40:50+09:00
Subject: Re: accessing index inside map

David A. Black wrote:
> Hi --
>
> On Mon, 11 Jul 2005, [iso-8859-1] "Pe�a, Botp" wrote:
>
>> OK, i'll be shooting for the moon here. How about passing a
>> parameter? Is it then possible to make #each or #map same behavior w
>> #each_with_index or #map_with_index or whatever *_with_index so that
>> the ff works,
>>
>> def each(with_index=true) do... end
>>
>> def map(with_index=true) do ... end
>>
>> and thus, we can do
>>
>> [1,2,3,4,5,6].map(true) {|x,i|[2,5].include?(i) ? x : x*2}
>
> I'd hope not to see that.  I'm actually hoping that maybe someday all
> the boolean flag methods (like instance_methods(true) etc.) will be
> changed :-)  They've always seemed to me to be the most cryptic thing
> in all of Ruby.

To second that: it's generally considered not very clean to have a flag
change a method's behavior.  I think this is a case where another method
is superior to having one method behavior switched.  Even from an
implementation perspective: either you end up with a single method that
consists of if-then-else on the top level with one implementation in each
branch or you end up with a lot of if-then-else inside the looping.  The
latter is inefficient and the former is more efficient but then you can
have to methods anyway.

Kind regards

    robert