Lis - lisp dialect with semantic whitespace

lis.txt

define sum term a next b
  define iter a result
    if
      > a b
      result
      iter
        next a
        +
          term a
          result
  iter a 0

# parens are allowed because practicality beats purity
# but syntax for let and lambda needs more work
 
define f x y
  let
      a (+ 1 (* x y))
      b (- 1 y)
    +
      * x (square a)
      * y b
      * a b

define f x y
  lambda a b
      +
        * x (square a)
        * y b
        * a b
    + 1 (* x y)
    - 1 y