-- ParserExpr.y
--
-- Turning this file into ParserExpr.hs:
--      happy ParserExpr.y -i
-- The above also creates an ParserExpr.info file, which is
-- useful for debugging.
--
-- To generate a parser that prints debugging information to stderr
-- use the following command:
--      happy ParserExpr.y -i -a -d



{
module ParserExpr where

import LexerExpr

}

%name parser
%tokentype { Token }
%error { parseError }


%token 
      '+'             { TokenPlus }
      '*'             { TokenMult }
      '-'             { TokenMinus }
      and             { TokenAnd }
      '!'             { TokenNot }
      int             { TokenNUM $$ }

%left '+' '-'
%left '*'
%left NEG

      
%%

	
Expr :
            Expr '+' Expr
            { Plus $1 $3 }

        |   Expr '*' Expr
            { Mult $1 $3 }

        |   Expr '-' Expr
            { Minus $1  $3 }

        |   '-' Expr %prec NEG
            { Neg $2 }

        |   int
            { Num $1 }


      
{
data AST =
        Plus AST AST
    |   Mult AST AST
    |   Minus AST AST
    |   Neg AST
    |   Num Int
    deriving Show


parseError :: [Token] -> a
parseError _ = error "Parse error"

}