-- Abstract expression trees as an intermediate representation language:
module IRTree(Exp(..),Stm(..),BinOp(..),RelOp(..),
              newlabel,extendlabel,newtemp,extendtemp) where

data Exp = CONST Int -- could be extended to other constants, like floats, chars
         | NAME Label          -- target of a jump
         | TEMP Temp           -- temporary value (e.g., register)
         | BINOP BinOp Exp Exp -- apply binary operator
         | MEM Exp             -- memory access
         | CALL Exp [Exp]      -- procedure call
         | ESEQ Stm Exp        -- expression with side effect
  deriving Show

data Stm = MOVE Exp Exp                    -- assignment
         | EXP Exp                         -- expression as statement
         | JUMP Exp                        -- unconditional jump
         | CJUMP RelOp Exp Exp Label Label -- conditional jump
         | SEQ Stm Stm                     -- sequence of statements
         | LABEL Label                     -- definition of a label
  deriving Show

data BinOp = PLUS| MINUS | MUL | DIV | MOD | AND | OR | LSHIFT | RSHIFT -- etc
  deriving Show

data RelOp = EQ | NE | LT | GT | LTE | GTE 
  deriving Show


------------------------------------------------------------------
-- Labels:

data Label = Label String
  deriving Show

newlabel :: Label -> Int -> Label
newlabel (Label l) i = Label (l ++ '$' : show i)

extendlabel :: Label -> Int -> Label
extendlabel (Label l) i = Label (l ++ '_' : show i)

------------------------------------------------------------------
-- Temporaries:

data Temp = Temp String
  deriving Show

newtemp :: Temp -> Int -> Temp
newtemp (Temp l) i = Temp (l ++ '$' : show i)

extendtemp :: Temp -> Int -> Temp
extendtemp (Temp l) i = Temp (l ++ '_' : show i)