-- File generated by the BNF Converter.
-- Parser definition for use with Happy.
{
{-# OPTIONS_GHC -fno-warn-incomplete-patterns -fno-warn-overlapping-patterns #-}
{-# LANGUAGE PatternSynonyms #-}

module ParCalc
  ( happyError
  , myLexer
  , pExp
  , pExp1
  , pExp2
  ) where

import Prelude

import qualified AbsCalc
import LexCalc

}

%name pExp Exp
%name pExp1 Exp1
%name pExp2 Exp2
%monad { Err } { (>>=) } { return }
%tokentype {Token}

%token
  '(' { PT _ (TS _ 1) }
  ')' { PT _ (TS _ 2) }
  '*' { PT _ (TS _ 3) }
  '+' { PT _ (TS _ 4) }
  '-' { PT _ (TS _ 5) }
  '/' { PT _ (TS _ 6) }
  L_integ { PT _ (TI $$) }

%%

Integer :: { Integer }
Integer  : L_integ  { (read $1 ) :: Integer }

Exp :: { AbsCalc.Exp }
Exp
  : Exp '+' Exp1 { AbsCalc.EAdd $1 $3 }
  | Exp '-' Exp1 { AbsCalc.ESub $1 $3 }
  | Exp1 { $1 }

Exp1 :: { AbsCalc.Exp }
Exp1
  : Exp1 '*' Exp2 { AbsCalc.EMul $1 $3 }
  | Exp1 '/' Exp2 { AbsCalc.EDiv $1 $3 }
  | Exp2 { $1 }

Exp2 :: { AbsCalc.Exp }
Exp2
  : '(' Exp ')' { $2 }
  | Integer { AbsCalc.EInt $1 }

{

type Err = Either String

happyError :: [Token] -> Err a
happyError ts = Left $
  "syntax error at " ++ tokenPos ts ++ 
  case ts of
    []      -> []
    [Err _] -> " due to lexer error"
    t:_     -> " before `" ++ (prToken t) ++ "'"

myLexer :: String -> [Token]
myLexer = tokens

}