[Python-Dev] one last SRE headache

[Fredrik Lundh]

tim peters:
> The PRE documentation expresses the true intent:
> 
>     \number
>     Matches the contents of the group of the same number. Groups
>     are numbered starting from 1. For example, (.+) \1 matches 'the the'
>     or '55 55', but not 'the end' (note the space after the group). This
>     special sequence can only be used to match one of the first 99 groups.
>     If the first digit of number is 0, or number is 3 octal digits long,
>     it will not be interpreted as a group match, but as the character with
>     octal value number.

yeah, I've read that.  clear as coffee.

but looking at again, I suppose that the right way to
implement this is (doing the tests in the given order):

    if it starts with zero, it's an octal escape
    (1 or 2 octal digits may follow)

    if it starts with an octal digit, AND is followed
    by two other octal digits, it's an octal escape

    if it starts with any digit, it's a reference
    (1 extra decimal digit may follow)

oh well.  too bad my scanner only provides a one-character
lookahead...

</F>