Functional Ruby

gistfile1.txt

# Not that this is an impressive demo, but it makes the point that Ruby
# does in fact have the ability to create "pure" functions and pass them
# as arguments to higher order functions. People get hung up on the syntax
# but it's not really that complicated.

make_adder = method def make_adder(num)
  ->(input){ input + num }
end

make_add_twice = method def make_add_twice(adder, num)
  ->{ adder[num] + adder[num] }
end

result_getter = method def result_getter(function)
  function.call
end

add1 = make_adder(1)
four = make_add_twice(add1, 1)
puts "four!" if result_getter(four) == 4