Subdivide a list into sub-lists of specified length

subdv.rb

# @param [Array<Integer>] List of sizes of the partitions self will be subdivided into
# @return [Object] Array containing self divided into one or more sub-arrays of size n
# @example
#   [1,2,3].subdv [1]      #=> [[1]]
#   [1,2,3].subdv [3]      #=> [[1,2,3]]
#   [1,2,3].subdv [1,2]    #=> [[1],[2,3]]
#   [1,2,3].subdv [1,2]    #=> [[1],[2,3]]
#   [1,2,3].subdv [1,1,1]  #=> [[1],[2],[3]]
#   [1,2,3].subdv [1,2,1]  #=> [[1],[2,3],[]]
def subdv(arr)
  arr.reduce([]) { |ret, n| ret << self.slice!(0..n-1) }
end