-- See the README file for an example session.

module Main where

import Foreign.MathLink

addFour :: (Int,Int,Int,Int) -> IO Int
addFour (a,b,c,d) = return $ a+b+c+d

-- Note that functions to be exposed need to be uncurried. 
ackermann :: (Integer,Integer) -> IO Integer
ackermann (m,n) = return $ ack m n

ack :: Integer -> Integer -> Integer
ack 0 n = n + 1
ack 1 n = n + 2
ack 2 n = 2 * n + 3
ack m 0 = ack (m-1) 1
ack m n = ack (m-1) (ack m (n-1))

decl :: MLSpec
decl = 
  [ Eval $ "BeginPackage":@[St "Test`"]

  , DeclMsg "AddFour" "usage" 
      "AddFour[a,b,c,d] returns the sum of a, b, c, and d."
  , DeclMsg "Ackermann" "usage" 
      "Ackermann[m,n]: the Ackermann function."

  , Eval $ "Begin":@[St "`Private`"]

  , DeclFn { 
      callPattern = "AddFour[a_Integer,b_Integer,c_Integer,d_Integer]"
    , argPattern = "{a,b,c,d}"
    , func = addFour
    }
  , DeclFn {
      callPattern = "Ackermann[i_Integer,j_Integer]"
    , argPattern = "{i,j}"
    , func = ackermann
    }

  , Eval $ "End":@[]
  , Eval $ "EndPackage":@[]
  ]

main :: IO ()
main = runMathLink decl