%semantic token '=' '-' '+' '*' '/' 
%right '=' 
%left '-' '+' 
%left '*' '/' 
%left NEG 
%tree

%%

line:
      exp  
;
exp:
      %name NUM
      NUM
    | %name VAR
      VAR
    | %name ASSIGN
      VAR '=' exp
    | %name PLUS
      exp '+' exp
    | %name MINUS
      exp '-' exp
    | %name TIMES
      exp '*' exp
    | %name DIV
      exp '/' exp
    | %name UMINUS
      '-' exp %prec NEG
    | '(' exp ')'  /* Let us simplify a bit the tree */
;

%%