Array Element Diffing

Finding included and excluded elements between two arrays.

• Using a set difference, you can check if one array includes all elements of another.

not_included = [1,2,3] - (1..9).to_a
not_included # []

not_included = [1,2,3,'A'] - (1..9).to_a
not_included # ["A"]

Use each_slice to chop up array by x number of elements

batch_size = 2
arr.each_slice(batch_size) { |batch| batch*2 }

(1..10).each_slice(3) { |a| p a }
# outputs below
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
[10]

Grab n-number of elements from beginning or end of array

Use Array.first(x) to grab x-number of elements in the front of the array.

Grabbing from end to front would be Array.last(x).

a = [ "q", "r", "s", "t" ]
a.first     # "q"
a.first(2)  # ["q", "r"]