ckirkendall

(defrecord Tree [left elm right])

(defprotocol Monoid
   (append [a b] )
   (identity [a] ))

(defprotocol Foldable
  (foldl [l f i])
  (mfirst [l]))
  

ckirkendall

object Lambda extends App {
  val number = (num: Int) => (env: Map[Symbol, Int]) => num
  val variable = (id: Symbol) => (env: Map[Symbol, Int]) => env(id)
  val add = (a: (Map[Symbol, Int]) => Int, b: (Map[Symbol, Int]) => Int ) => (env: Map[Symbol, Int]) => a(env) + b(env)
  val multiply = (a: (Map[Symbol, Int]) => Int, b: (Map[Symbol, Int]) => Int ) => (env: Map[Symbol, Int]) => a(env) * b(env)
  
  val environment = Map('a -> 1, 'b -> 2, 'c -> 3)
  val expr_tree = add(variable('a), multiply(number(2), variable('b)))

  println(expr_tree(environment))

ckirkendall

Number   = lambda { |env, num| num }
Variable = lambda { |env, var| env[var] }
Add      = lambda { |env, a, b| evaluate(env, a) + evaluate(env, b) }
Multiply = lambda { |env, a, b| evaluate(env, a) * evaluate(env, b) }

def evaluate(env, exp)
  op, *args = exp
  op.(env, *args)
end

ckirkendall

(use '[clojure.core.match :only [match]])

(defn evaluate [env [sym x y]]
  (match [sym]
    ['Number]   x
    ['Add]      (+ (evaluate env x) (evaluate env y))
    ['Multiply] (* (evaluate env x) (evaluate env y))
    ['Variable] (env x)))
    
(def environment {"a" 3, "b" 4, "c" 5})