split array to sub array by step in Ruby

Question

In Python i can slice array with "jump-step". Example:

In [1]: a = [1,2,3,4,5,6,7,8,9] 

In [4]: a[1:7:2] # start from index = 1 to index < 7, with step = 2
Out[4]: [2, 4, 6]

Can Ruby do it?

Answer 1

a = [1,2,3,4,5,6,7,8,9]
a.values_at(*(1...7).step(2)) - [nil]
#=> [2, 4, 6] 

Although in the above case the - [nil] part is not necessary, it serves just in case your range exceeds the size of the array, otherwise you may get something like this:

a = [1,2,3,4,5,6,7,8,9]
a.values_at(*(1..23).step(2))
#=> [2, 4, 6, 8, nil, nil, nil, nil, nil, nil, nil, nil]

Answer 2

In ruby, to get the same output:

a = [1,2,3,4,5,6,7,8,9]
(1...7).step(2).map { |i| a[i] }
=> [2, 4, 6]