type checking

type_checking.rb

# gem install mar
# this only checks at runtime, so it doesn't verify the type at compilation

require 'mar'

def type_check(type, value)
  value.is_a?(type) or raise "#{value} is not type of #{type}"
end

def type_signature(*types)
  ->(original, *args, &blk) do
    types[0..-2].zip(args).each do |(type, arg)|
      type_check(type, arg)
    end

    result = original.call(1, 2, &blk)
    type_check(types[-1], result)
    result
  end
end

class Foo
  _ type_signature(Integer, Integer, Integer)
  def foo(one_arg, two_arg)
    one_arg + two_arg
  end
end

puts Foo.new.foo(1, 2)
# => 3

puts Foo.new.foo(1, 'a')
# raises: a is not type of Integer