gistfile1.hs

data Op = Integer Int | Function String deriving (Show)
newtype Program = List Op
data Ast = Const Int | Binary Ast String Ast

--i robisz funkcje
--Ast -> Program
--koniec

value (Integer val)  = val

sample_input = [Integer 1, Integer 5, Function "+", Integer 6, Function "*", Integer 67, Integer 13, Integer 49, Function "+", Function "-", Function "+" ]

-- just put shit on stacks
eval0 [] num_stack foo_stack = (num_stack, foo_stack)
eval0 (i:is) num_stack foo_stack = 
	case i of
		Integer  num -> eval0 is (num : num_stack) foo_stack
		Function foo -> eval0 is num_stack (foo : foo_stack)

-- perform some calculations
eval1 [] num_stack = num_stack
eval1 (i:is) num_stack = 
	case i of
		Integer  num -> eval1 is (num : num_stack) 
		Function foo -> eval1 is (eval_foo foo num_stack) 

eval_foo foo num_stack = 
	case foo of
		"+" -> eval_op (+) num_stack --eval_plus  num_stack
		"-" -> eval_op (-) num_stack --eval_minus num_stack
		"*" -> eval_op (*) num_stack --eval_mul   num_stack
-- switch to doubles		"/" -> eval_div   num_stack

eval_op foo num_stack =
	let right = head num_stack in
	  let left = head $ tail num_stack in
	    (foo left right) : (tail $ tail num_stack) 	

--eval_plus num_stack = 
--	let left = head num_stack in
--	  let right = head $ tail num_stack in
--	    (left + right) : (tail $ tail num_stack) 

--eval_minus num_stack = 
--	let left = head num_stack in
--	  let right = head $ tail num_stack in
--	    (left - right) : (tail $ tail num_stack) 

--eval_mul num_stack = 
--	let left = head num_stack in
--	  let right = head $ tail num_stack in
--	    (left * right) : (tail $ tail num_stack) 

-- type system super fucker
--eval_div num_stack = 
--	let left = head num_stack in
--	  let right = head $ tail num_stack in
--	    (left / right) : (tail $ tail num_stack) 

-- transform to normal 2 + 4 
eval2 [] num_stack normal_stack = reverse $ concat normal_stack
eval2 (i:is) num_stack normal_stack = 
	case i of
		Integer  num -> eval2 is (num : num_stack) normal_stack
		Function foo -> eval2 is num_stack ((eval2_foo foo num_stack) : normal_stack)

eval2_foo foo num_stack = 
	let right = head num_stack in
		let left = head $ tail num_stack in
		  [Integer left, Function foo, Integer right]

result0 = eval0 sample_input [] [] 
result1 = eval1 sample_input [] 
result2 = eval2 sample_input [] []

main = do
	putStr "Initial input  : "
	putStrLn $ show sample_input

	putStr "Result of eval0: "
	putStrLn $ show result0

	putStr "Result of eval1: "
	putStrLn $ show result1

	putStr "Result of eval2: "
	putStrLn $ show result2