Hi,I am trying to build simple calculator using ANTLR program.I wrote below grammar on ANTLR4, the idea is to generate visitor class and compute.

grammar Calculator; // Lexer specification fragment

LETTER : 'a'..'z' | 'A'..'Z'; fragment DIGIT : '0'..'9'; ID : LETTER (LETTER | DIGIT)*; NUM : DIGIT+; ADD : '+'; SUB : '-'; MUL : '*'; DIV : '/'; LPAR : '('; RPAR : ')'; ASSIGN : '='; NEWLINE : ' '?' '; WS : (' ' | '\t' | ' ' | ' ')+ { skip(); }; // Parser specification program : stmt_list+; stmt_list : stmt ; stmt : expr NEWLINE # 'printExpr' | ID ASSIGN expr # 'assigned' | NEWLINE # 'blank' ; expr : term (ADD term | SUB term)* #'AddSub' ; term : factor (MUL factor | DIV factor)* #'MulDiv' ; factor : LPAR expr RPAR #'parens' | ID #'id' | NUM #'num'

But while compiling the grammar,it's giving below error.

line 8:46 no viable alternative at character '#'

line 9:46 no viable alternative at character '#'

line 10:46 no viable alternative at character '#'

line 11:46 no viable alternative at character '#'

line 12:46 no viable alternative at character '#'

Am I writing some incorrect syntax?