[Pyparsing] Getting "maximum recursion depth exceeded" when using Forward

[mayamatakeshi <may...@gm...>]

Hello, I am getting "maximum recursion depth exceeded" with the below:

#####################################
from pyparsing import *

key = oneOf(['env', 'name'])
val = Word(alphas)
keyEqVal = key + '=' + val
enclosed = Forward()
nestedParens = nestedExpr('(', ')', content=enclosed)
boolExpr = enclosed + oneOf(["and", "or"]) + enclosed
enclosed << (boolExpr | nestedParens | keyEqVal)

data = 'e=prod'
print enclosed.parseString(data)
#####################################

I know it is due my definition of boolExpr, but I could not figure out how
to correct it.

R,
Takeshi