There is a simple example in BNFC's documentation.
Char_a. Char ::= "a" ;
Char_b. Char ::= "b" ;
I try to rewrite it by using union |
Char_a. Char ::= "a" | "b" ;
but then in this case I got an error bnfc: user error (syntax error at line 1 before | b ;)
It seems that BNFC really not likes |. However, I find | can be used in rules statement.
rules Boolen ::= "True" | "False";
this can be compiled successfully. So I would like to know the reason for the error in my rewriting and where the union symbol can be used.