23 def p_statement_assign(t):  argument
25     names[t[1]] = t[3]
27 def p_statement_assign_2(t):  argument
29     names[t[1]] = t[3]
31 def p_statement_expr(t):  argument
33     print(t[1])
35 def p_expression_binop(t):  argument
40     if t[2] == '+'  : t[0] = t[1] + t[3]
41     elif t[2] == '-': t[0] = t[1] - t[3]
42     elif t[2] == '*': t[0] = t[1] * t[3]
43     elif t[2] == '/': t[0] = t[1] / t[3]
45 def p_expression_uminus(t):  argument
47     t[0] = -t[2]
49 def p_expression_group(t):  argument
51     t[0] = t[2]
53 def p_expression_number(t):  argument
55     t[0] = t[1]
57 def p_expression_name(t):  argument
60         t[0] = names[t[1]]
62         print("Undefined name '%s'" % t[1])
63         t[0] = 0
65 def p_error(t):  argument
66     print("Syntax error at '%s'" % t.value)