# -----------------------------------------------------------------------------# yacc_unused.py## A grammar with an unused rule# -----------------------------------------------------------------------------import syssys.tracebacklimit = 0from calclex import tokens# Parsing rulesprecedence = (    ('left','PLUS','MINUS'),    ('left','TIMES','DIVIDE'),    ('right','UMINUS'),    )# dictionary of namesnames = { }def p_statement_assign(t):    'statement : NAME EQUALS expression'    names[t[1]] = t[3]def p_statement_expr(t):    'statement : expression'    print t[1]def p_expression_binop(t):    '''expression : expression PLUS expression                  | expression MINUS expression                  | expression TIMES expression                  | expression DIVIDE expression'''    if t[2] == '+'  : t[0] = t[1] + t[3]    elif t[2] == '-': t[0] = t[1] - t[3]    elif t[2] == '*': t[0] = t[1] * t[3]    elif t[3] == '/': t[0] = t[1] / t[3]def p_expression_uminus(t):    'expression : MINUS expression %prec UMINUS'    t[0] = -t[2]def p_expression_group(t):    'expression : LPAREN expression RPAREN'    t[0] = t[2]def p_expression_number(t):    'expression : NUMBER'    t[0] = t[1]def p_expression_name(t):    'expression : NAME'    try:        t[0] = names[t[1]]    except LookupError:        print "Undefined name '%s'" % t[1]        t[0] = 0def p_expr_list(t):    'exprlist : exprlist COMMA expression'    passdef p_expr_list_2(t):    'exprlist : expression'    passdef p_error(t):    print "Syntax error at '%s'" % t.valueimport yaccyacc.yacc()