# 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)
from tdparser import Lexer, Parser, Token, ParserError
from tdparser.topdown import EndToken
__all__ = ['parse_expression', 'parse_expressions']
def escape_string(text):
return '"%s"' % text.replace('\\', '\\\\').replace('"', '\\"')
def unescape_string(text):
assert text[0] == text[-1] == '"'
return text[1:-1].replace('\\"', '"').replace('\\\\', '\\')
lexer = Lexer()
class Key(Token):
regexp = r'[A-Za-z_][A-Za-z0-9_]*'
def nud(self, context):
return self
class Number(Token):
regexp = r'-?\d+'
type = 'int'
def __init__(self, text):
Token.__init__(self, text)
