Default value for an implicit block

ruby.rb

  def assert_sorted array, &block
    block ||= lambda {|i,j| i+1 < j+1}
    assert array.each_cons(2).all?(&block), 'Result data not correctly sorted'
  end
    
  assert_sorted [1,3,5] {|i,j| i+1 < j+1} #works
  assert_sorted [1,3,5]      #triggers:
  
  ArgumentError:   wrong number of arguments (1 for 2)
  ruby.rb:2:in `block in assert_sorted'
  ruby.rb:3:in `each'
  ruby.rb:3:in `each_cons'
  ruby.rb:3:in `each'
  ruby.rb:3:in `all?'
  ruby.rb:3:in `assert_sorted'
  ruby.rb:7:in `test_scopes'