Section an array by the given lengths

section.rb

# section :: [a] -> [Int] -> [[a]]
section = lambda { |arr:, lengths:|
  starts = [*0..lengths.size - 1].reduce([]) do |acc, idx|
    acc << lengths.take(idx).sum; acc
  end

  starts.zip(lengths).map { |start, lenght| arr.slice(start, lenght) }
}

arr = [*1..100]
lengths = [28, 31, 32, 9]

p section.call(arr: arr, lengths: lengths).map(&:length) == lengths
p section.call(arr: arr, lengths: lengths)

# [
#   [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], # 12
#   [13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23], # 11
#   [24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45], # 22
#   [46, 47, 48, 49, 50] # 5
# ]