import ply.lex as lex
import ply.yacc as yacc

# List of token names.   This is always required
tokens = (
    'VARIABLE',
    'OR',
    'AND',
    'PAR_OPEN',
    'PAR_CLOSE',
)

# Regular expression rules for simple tokens
t_ignore        = ' t'
t_VARIABLE      = r'b[a-z]+b'
t_OR            = r'bORb'
t_AND           = r'bANDb'
t_PAR_OPEN      = r'('
t_PAR_CLOSE     = r')'

def t_error(t):
    print("Illegal character '%s'" % t.value[0])
    t.lexer.skip(1)

# Build the lexer
lexer = lex.lex()

def p_term(p):
    '''term : VARIABLE OR VARIABLE
            | VARIABLE AND VARIABLE
            | PAR_OPEN VARIABLE AND VARIABLE PAR_CLOSE'''

    if p[2] == 'AND':
        p[0] = "".join([p[1], p[3]])

    for idx, val in enumerate(p):
        print(idx, val)

def p_error(p):
    print("Syntax error in input!")
    print(p)


parser = yacc.yacc()
res = parser.parse("(a AND b)")
print(res)

expression : expression + term
            | expression - term
            | term

 term       : term * factor
            | term / factor
            | factor

 factor     : NUMBER
            | ( expression )