ruby inject sum

How to sum array members in Ruby?

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1

I have an array of integers.

For example:

array = [123,321,12389]

Is there any nice way to get the sum of them?

I know, that

sum = 0
array.each { |a| sum+=a }

would work.

ruby arrays math sum

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edited Oct 8 '09 at 21:21 Mike Woodhouse 12.1k 1 14 35

asked Oct 8 '09 at 16:04 brainfck 721 110 90% accept rate

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4 Answers

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up vote 12 down vote accepted

Try this:

array.inject{|sum,x| sum + x }

Documentation

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answered Oct 8 '09 at 16:07 zenazn 2,835915

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jorney's array.inject(:+) is more efficient. – Peter Oct 9 '09 at 7:09

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up vote 4 down vote

Add sum to the Array class

class Array
    def sum
        self.inject{|sum,x| sum + x }
    end
end

Then do fun stuff like:

[1,2,3,4].sum

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answered Oct 8 '09 at 18:29 jrhicks 1,528215

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I've done this before, very useful :-) – Topher Fangio Oct 8 '09 at 18:30

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up vote 4 down vote

Alternatively (just for comparison), if you have Rails installed (actually just ActiveSupport):

require 'activesupport'
array.sum

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answered Oct 8 '09 at 16:49 Mike Woodhouse 12.1k11435

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up vote 19 down vote

Or try the ruby 1.9 way

array.inject(:+)

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answered Oct 8 '09 at 16:28 jomey 1913

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Also works with 1.8.7 – glenn jackman Oct 8 '09 at 16:29

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Also works with Rails – khelll Oct 8 '09 at 18:30

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beautiful, you made my day – marcgg Dec 23 '09 at 13:39

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