[Pyparsing] [pyparsing] RecursiveGrammarException

[Haifeng <min...@gm...>]

Hi

I am new to pyparsing. I am trying to parse just the following C
expressions:
a
a->b

My code looks like:

from pyparsing import *

ARROW = Literal('->')
identifier = Word(alphas+"_", alphanums+"_")

primary_expression = identifier

postfix_expression = Forward()
postfix_expression << ( primary_expression | (postfix_expression + ARROW +
identifier))

But it failed on postfix_expression.validate(). What did I do wrongly here?
Thanks