-- | An example atom design.
module Language.Atom.Example
  ( compileExample
  , example
  ) where

import Language.Atom

-- | Invoke the atom compiler.
compileExample :: IO ()
compileExample = compile "example" defaults { cPreCode = preCode, cPostCode = postCode } example

preCode :: String
preCode = unlines
  [ "#include <stdlib.h>"
  , "#include <stdio.h>"
  , "unsigned long int a;"
  , "unsigned long int b;"
  , "unsigned char running = 1;"
  ]

postCode :: String
postCode = unlines
  [ "int main(int argc, char* argv[]) {"
  , "  a = atoi(argv[1]);"
  , "  b = atoi(argv[2]);"
  , "  printf(\"Computing the GCD of %i and %i...\\n\", a, b);"
  , "  while(running) {"
  , "    example();"
  , "    printf(\"iteration:  a = %i  b = %i\\n\", a, b);"
  , "  }"
  , "  printf(\"GCD result: %i\\n\", a);"
  , "  return 0;"
  , "}"
  ]


-- | An example design that computes the greatest common divisor.
example :: Atom ()
example = do

  -- External reference to value A.
  a <- word32' "a"

  -- External reference to value B.
  b <- word32' "b"

  -- The external running flag.
  running <- bool' "running"

  -- A rule to modify A.
  atom "a_minus_b" $ do
    cond $ value a >. value b
    a <== value a - value b

  -- A rule to modify B.
  atom "b_minus_a" $ do
    cond $ value b >. value a
    b <== value b - value a

  -- A rule to clear the running flag.
  atom "stop" $ do
    cond $ value a ==. value b
    running <== false