How to compare values in an Array

Question

Let's say I have an array

array = [1,2,3,4,5]

How do I compare the first with the second value, the second with the third etc.

The only thing I could come up with is this (which is rather ugly)

compared = array.each_with_index.map do |a,i| 
  array[i+1].nil? ? nil : array[i] - array[i + 1]
end

compared.compact # to remove the last nil value

What I want is

[-1, -1, -1, -1]

Is there a nice "ruby way" of achieving this? without using all the ugly array[i] and array[i+1] stuff.

falsetru · Accepted Answer · 2013-11-26 13:20:12Z

9

array = [1,2,3,4,5]
array.each_cons(2).map { |a,b| a - b }
# => [-1, -1, -1, -1]

answered Nov 26, 2013 at 13:20

falsetru

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Comments

uncutstone · Accepted Answer · 2013-11-26 14:03:06Z

1

You can also use Enumerable#inject：

a = [1,2,3,4,5]
b = []
a.inject{|i,j| b<< i-j; j}
p b

result：

[-1, -1, -1, -1]

answered Nov 26, 2013 at 14:03

uncutstone

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