# of same precedence
right_side = context.expression(self.lbp)
return left + right_side
class Substraction(Token):
lbp = 10 # Same precedence as addition
def led(self, left, context):
return left - context.expression(self.lbp)
def nud(self, context):
"""When a '-' is present on the left of an expression."""
# This means that we are returning the opposite of the next expression
return - context.expression(self.lbp)
class Multiplication(Token):
lbp = 20 # Higher precedence than addition/substraction
def led(self, left, context):
return left * context.expression(self.lbp)
lexer = Lexer(with_parens=True)
lexer.register_token(Integer, re.compile(r'\d+'))
lexer.register_token(Addition, re.compile(r'\+'))
lexer.register_token(Substraction, re.compile(r'-'))
lexer.register_token(Multiplication, re.compile(r'\*'))
def parse(text):
return lexer.parse(text)
# Fetch the expression to the right, stoping at the next boundary
# of same precedence
right_side = context.expression(self.lbp)
return left + right_side
class Substraction(Token):
lbp = 10 # Same precedence as addition
def led(self, left, context):
return left - context.expression(self.lbp)
def nud(self, context):
"""When a '-' is present on the left of an expression."""
# This means that we are returning the opposite of the next expression
return - context.expression(self.lbp)
class Multiplication(Token):
lbp = 20 # Higher precedence than addition/substraction
def led(self, left, context):
return left * context.expression(self.lbp)
lexer = Lexer(with_parens=True)
lexer.register_token(Integer, re.compile(r'\d+'))
lexer.register_token(Addition, re.compile(r'\+'))
lexer.register_token(Substraction, re.compile(r'-'))
lexer.register_token(Multiplication, re.compile(r'\*'))
def parse(text):
return lexer.parse(text)
class Power(Token):
lbp = 30 # Higher than mult
def led(self, left, context):
# We pick expressions with a lower precedence, so that
# 2 ** 3 ** 2 computes as 2 ** (3 ** 2)
return left ** context.expression(self.lbp - 1)
class Log(Token):
lbp = 30 # Higher than mult
def nud(self, context):
return log(float(context.expression(self.lbp - 1)))
lexer = Lexer(with_parens=True)
lexer.register_token(Integer, re.compile(r'\d+'))
lexer.register_token(Float, re.compile(r'\d+\.\d+'))
lexer.register_token(Addition, re.compile(r'\+'))
lexer.register_token(Substraction, re.compile(r'-'))
lexer.register_token(Multiplication, re.compile(r'\*'))
lexer.register_token(Division, re.compile(r'/'))
lexer.register_token(Power, re.compile(r'\*\*'))
lexer.register_token(Log, re.compile(r'log'))
def parse(text):
return lexer.parse(text)
class LeftParen(Token):
match = RightParen
def nud(self, context):
expr = context.expression()
context.consume(expect_class=self.match)
return expr
def __repr__(self):
return '<(>'
# регистрация токенов
lexer = Lexer()
lexer.register_tokens(Integer, Addition, Multiplication, Division)
lexer.register_token(LeftParen, re.compile(r'\('))
lexer.register_token(RightParen, re.compile(r'\)'))
def parse(text):
"""Преобразует лексические токены в представление"""
return lexer.parse(text)
print("(((10+1)*(5+6/(3+1))+4*(3+1)))")
print(
f'Результат вычеслений после разбора: {parse("(((10+1)*(5+6/(3+1))+4*(3+1)))")}'
)
