Blocks

With our monad we’ll create several functions to manipulate the current block state so that we can push and pop the block “cursor” and append instructions into the current block.

  1. entry :: Codegen Name
  2. entry = gets currentBlock
  4. addBlock :: String -> Codegen Name
  5. addBlock bname = do
  6.   bls <- gets blocks
  7.   ix  <- gets blockCount
  8.   nms <- gets names
  10.   let new = emptyBlock ix
  11.       (qname, supply) = uniqueName bname nms
  13.   modify $ \s -> s { blocks = Map.insert (Name qname) new bls
  14.                    , blockCount = ix + 1
  15.                    , names = supply
  16.                    }
  17.   return (Name qname)
  19. setBlock :: Name -> Codegen Name
  20. setBlock bname = do
  21.   modify $ \s -> s { currentBlock = bname }
  22.   return bname
  24. getBlock :: Codegen Name
  25. getBlock = gets currentBlock
  27. modifyBlock :: BlockState -> Codegen ()
  28. modifyBlock new = do
  29.   active <- gets currentBlock
  30.   modify $ \s -> s { blocks = Map.insert active new (blocks s) }
  32. current :: Codegen BlockState
  33. current = do
  34.   c <- gets currentBlock
  35.   blks <- gets blocks
  36.   case Map.lookup c blks of
  37.     Just x -> return x
  38.     Nothing -> error $ "No such block: " ++ show c