recurcion_foldBack.rb

recurcion_foldBack.rb

#!/usr/bin/env ruby
# coding:utf-8

list = [1, 2, 3, 4]

sumproc = Proc.new{|initval, enum|
  initval + enum
}

minproc = Proc.new{|initval, enum|
  initval > enum ? enum : initval
}

maxproc = Proc.new{|initval, enum|
  initval < enum ? enum : initval
}


def foldBack(list, initval, sumproc)
  if list.size == 0
    initval
  else
    enum = list.shift
    calcresult = sumproc.call(initval, enum)
    foldBack(list, calcresult, sumproc)
  end
end

puts foldBack(list.clone, 0, sumproc)
puts foldBack(list.clone, list[0], minproc)
puts foldBack(list.clone, list[0], maxproc)