From: Rick DeNatale <rick.denatale@...>
Date: 2008-06-12T07:49:18+09:00
Subject: Re: Array inject function problem

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On Wed, Jun 11, 2008 at 5:50 PM, Tim Hunter <TimHunter@nc.rr.com> wrote:

> Jason Lillywhite wrote:
>
>> So let me ask you this:
>>
>> going back to
>>
>> sum = [1,3,5].inject(0) {|s,e| s+e}
>> puts sum
>>
>> what if you want to return an array that shows each step of the way, such
>> that:
>>
>> sum => [1,4,9]
>>
>> ??
>>
> irb(main):003:0> steps = []
> => []
> irb(main):004:0> sum = [1,3,5].inject(0) {|s,e| steps << s+e; steps.last}
> => 9
> irb(main):005:0> p steps
> [1, 4, 9]


Here's a way to do it without the extra variable:

 [1,3,5].inject([]) {|s,e| s = s.to_a; s << e + ( s.last || 0)}

or if you still want to inject 0 as the starting value:

[1,3,5].inject(0) {|s,e| s = s.to_a; s << e + s.last}[1..-1]

Now these will give a deprecation warning since Ruby 1.9 does away with
Object#to_a, an alternative is:

 [1,3,5].inject(0) {|s,e| s = [s].flatten; s << e + s.last}[1..-1]


-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/

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