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yacc: e - line 85 of "tac.y", a token appears on the lhs of a production

What is the exact meaning of the error: yacc: e - line 85 of "tac.y", a token appears on the lhs of a production

line 85: 

T:  INT { strcpy($$.type,"int"); }
            |
             REAL { strcpy($$.type,"real"); }

I have associated a attribute to T

%union{
  struct attribute{
    char name[20];
    char type[20];
  }attr;
}
%token <attr> ID
%token <attr> E
%token <attr> T
Solution

  • It means what it says: that you are attempting to provide a derivation for a token. Tokens come from the lexcal analysis, so they cannot have grammatical rules associated with them.

    I guess you meant to declare the (semantic value) type of T:

    %type <attr> T

    You probably need to change the declaration of E too.

    Avoiding this kind of confusion is one of the reasons it is common to use ALL_CAPS for terminals (tokens) and lower-case for non-terminals.