Re: [Pyparsing] Unordered set of expressions

[Paul M. <pt...@au...>]

Russell -

I'm not seeing this behavior:


from pyparsing import *

"""
language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) &
ZeroOrMore(expr5)
"""

A = Literal("A")
B = Literal("B")
C = Literal("C")
D = Literal("D")
E = Literal("E")

lang = A & B & Optional(C) & ZeroOrMore(D) & ZeroOrMore(E)

tests = """\
    ABCDE
    ABDE
    AB
    BA
    EDCBA
    EAEB
    BEDCADEEDEDDEDD""".splitlines()

for t in tests:
    print t
    print lang.parseString(t, parseAll=True)
    print

prints:

    ABCDE
['A', 'B', 'C', 'D', 'E']

    ABDE
['A', 'B', 'D', 'E']

    AB
['A', 'B']

    BA
['B', 'A']

    EDCBA
['E', 'D', 'C', 'B', 'A']

    EAEB
['E', 'A', 'E', 'B']

    BEDCADEEDEDDEDD
['B', 'E', 'D', 'C', 'A', 'D', 'E', 'E', 'D', 'E', 'D', 'D', 'E', 'D', 'D']


All of my test cases parse successfully.  This is using the latest
pyparsing.

You can have as many D's and E's as you like, anywhere, and at most 1 C
anywhere, but you must have 1 A and 1 B, somewhere.

-- Paul


-----Original Message-----
From: Russell Dill [mailto:Rus...@as...] 
Sent: Thursday, September 29, 2011 1:25 PM
To: pyp...@li...
Subject: [Pyparsing] Unordered set of expressions

I have to parse something with an unordered set of expressions. In the
simplest case, some expressions are required, some are optional. For
this, parsing is easy:

language = expr1 & expr2 & Optional(expr3)

However, there are cases where an expression can occur zero or more
times, one or more times, or two or more times. But since they can
still occur in any order, I'm not sure how to handle it. If I try:

language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) &
ZeroOrMore(expr5)

Then parsing fails if all expr4's are not adjacent. My current idea is
to do the following:

multiples = ZeroOrMore(expr4 | expr5)

language = (multiples + expr1) & (multiples + expr2) &
Optional(multiples + expr3) & multiples

While its ugly, I can't think of any other way to do it. Additionally,
it doesn't get me any closer to implementing OneOrMore in an unsorted
set of expressions.

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