How do I find the first two consecutive elements in my array of numbers?

Question

Using Ruby 2.4, I have an array of unique, ordered numbers, for example

[1, 7, 8, 12, 14, 15]

How do I find the first two elements whose differ

Answer 1

Here's an alternate method provided for educational purposes:

arr = [1, 7, 8, 12, 14, 15]

arr.each_cons(2).map {|v|v.reduce(:-)}.index(-1)