{
{-# LANGUAGE BangPatterns #-}
module CycRepmin where

import Control.Monad.Error
}

data Tree
  con Leaf
    x :: Int
  con Bin
    l : Tree
    r : Tree
  ext Show

data Root
  con Root
    t : Tree

itf Root
  visit dispatch
    inh ast :: Root
    syn t :: Tree

itf Tree
  visit dispatch
    inh ast :: Tree
  visit compdist cyclic
    inh g :: Int
    syn m :: Int
  visit result
    syn t :: Tree

datasem Root monad IO
  cyclic  -- reminder: turn on cycle checking
  clause Root
    t.g   = t.m
    lhs.t = t.t

datasem Tree monad IO
  clause Leaf
    lhs.t = Tree_Leaf lhs.g
    lhs.m = loc.x

  clause Bin
    default g = last
    visit compdist
      lhs.m = l.m `min` r.m
      lhs.t = Tree_Bin l.t r.t

{
test :: Tree -> IO Tree
test t = do
  let inh = Inh_Root_dispatch { ast_Inh_Root = Root_Root t }
  syn <- invoke_Root_dispatch dnt_Root inh
  let t = t_Syn_Root syn
  return t

main :: IO ()
main = do let exp = Tree_Bin (Tree_Leaf 1) (Tree_Bin (Tree_Leaf 2) (Tree_Leaf 3))
          x <- test exp
          putStrLn $ show x
}