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Possible Duplicate:
How to sum array members in Ruby?

Lets say I have this array 

@test = [1, 2, 3, 4]

Then I want to do:

@test[0] + @test[1] + @test[2] + @test[3]

Is there not a smarter, faster way of doing this?

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2 Answers2

4

You can do this:

@test.inject(:+)
iwasrobbed
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  • folds need the identity as initial value : `@test.inject(0, :+)` – tokland Jan 15 '12 at 21:46
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    Not with ruby, if you don't supply an initial value, it uses the first value in the collection as the initial value: http://ruby-doc.org/core-1.9.3/Enumerable.html – Jesse Pollak Jan 15 '12 at 21:50
  • @tokland: "If you do not explicitly specify an initial value for memo, then uses the first element of collection is used as the initial value of memo." (from [the docs](http://ruby-doc.org/core-1.9.3/Enumerable.html#method-i-inject) ) – steenslag Jan 15 '12 at 21:53
  • More directly: http://ruby-doc.org/core-1.9.3/Enumerable.html#method-i-inject – Dave Newton Jan 15 '12 at 21:53
  • jesse, steenslag: not for empty inputs: `[].inject(:+)`. I guess the OP wants a generic solution, not for 4 elements. – tokland Jan 15 '12 at 21:57
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sum = 0
@test.each { |el| sum+=el }
iwasrobbed
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falinsky
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  • that's ok for a lot of (imperative) languages, but in Ruby the (functional) `Enumerable#inject` is the idiomatic solution. – tokland Jan 15 '12 at 22:03