python
import ply.lex as lex
import ply.yacc as yacc
tokens = (
'NUMBER',
'PLUS',
'TIMES',
)
t_PLUS = r'\+'
t_TIMES = r'\*'
t_ignore = ' \t
'
def t_NUMBER(t):
r'\d+'
t.value = int(t.value)
return t
def t_error(t):
print(f"Unexpected character: {t.value[0]}")
t.lexer.skip(1)
lexer = lex.lex()
def p_expression_plus(p):
'expression : expression PLUS term'
p[0] = p[1] + p[3]
def p_expression_term(p):
'expression : term'
p[0] = p[1]
def p_term_times(p):
'term : term TIMES factor'
p[0] = p[1] * p[3]
def p_term_factor(p):
'term : factor'
p[0] = p[1]
def p_factor_number(p):
'factor : NUMBER'
p[0] = p[1]
def p_error(p):
print("Syntax error")
parser = yacc.yacc()
result = parser.parse("2 + 3 * 4")
print(result)
