proc

proc.rb

def calc(b)
  b.call(3, 2)
end

#def calc(&block)
#  block.call
#end

# calc { |a, b| p a+b }

add = ->(a,b) { a+b }
multi = ->(a,b) { a*b }

p calc add # 5
p calc multi # 6

p %w(foo bar).map(&:upcase)
p [1,2,3].map(&:to_s)

class Array
  alias :head :first
  def tail
    drop 1
  end

  def reduce_left(proc, acc=0)
    return acc if empty?
    proc.call(head, tail.reduce_left(proc, acc))
  end
end

p [1,2,3].head # 1
p [1,2,3].tail # [2,3]
p [1,2,3].reduce_left add # 6