Ruby Optional Proc

proc.rb

def call_maybe(x)
  if block_given?
    yield x
  else
    x
  end
end

call_maybe(2) { |x| x + 1 }
call_maybe(2)

=begin
This doesn't work

def call_maybe(x, &block = nil)
  if block
    block.call(x)
  else
    x
  end
end
=end

def call_maybe(y, fn = nil)
  if fn
    fn.call(y)
  else
    y
  end
end

call_maybe(1, ->(y) { y + 1 })
call_maybe(1)

def call_for_sure(z, fn = ->(z) { z + 1 })
  fn.call(z)
end

call_for_sure(1)
call_for_sure(1, ->(z) { z - 1 })