On 7 Dec 2006, at 21:47, Josiah Carlson wrote:
> Alastair Houghton <[EMAIL PROTECTED]> wrote:
>> On 7 Dec 2006, at 02:01, Josiah Carlson wrote:
>>> Alastair Houghton <[EMAIL PROTECTED]> wrote:
>>>> On 7 Dec 2006, at 01:01, Josiah Carlson wrote:
>>>>> If we don't want
>>>>> slicing, or if prodicing a slice would produce a semantically
>>>>> questionable state, then lets not do it.
>>>>
>>>> ...if you return match objects from slicing, you have problems
>>>> like m
>>>> [::-1].groups(). *I* don't know what that should return.
>>>
>>> I would argue that any 'step' != 1 has no semantically correct
>>> result
>>> for slicing on a match object, so we shouldn't support it.
>>
>> OK, but even then, if you're returning a match object, how about the
>> following:
>>
>>>>> m = re.match('(A)(B)(C)(D)(E)', 'ABCDE')
>>>>> print m[0]
>> ABCDE
>>>>> n = m[2:5]
>>>>> print list(n)
>> ['B', 'C', 'D']
>>>>> print n[0]
>> B
>>>>> print n.group(0)
>> B
>>
>> The problem I have with it is that it's violating the invariant that
>> match objects should return the whole match in group(0).
>
> If we were going to go with slicing, then it would be fairly
> trivial to
> include the whole match range. Some portion of the underlying
> structure
> knows where the start of group 2 is, and knows where the end of
> group 5
> is, so we can slice or otherwise use that for subsequent sliced
> groups.
But then you're proposing that this thing (which looks like a tuple,
when you're indexing it) should slice in a funny way. i.e.
m = re.match('(A)(B)(C)(D)(E)', 'ABCDE')
print m[0]
ABCDE
print list(m)
['ABCDE', 'A', 'B', 'C', 'D', 'E']
n = m[2:5]
print list(n)
['BCD', 'B', 'C', 'D']
print len(n)
4
p = list(m)[2:5]
print p
['B', 'C', 'D']
print len(p)
Or are you saying that
m[2:5][0] != m[2:5].group(0)
but
m[0] == m.group(0)
??
Either way I think that's *really* counter-intuitive.
Honestly, I don't think that slicing should be supported if it's
going to have to result in match objects, because I can't see a way
to make them make sense.
I think that's Frederik's objection also, but unlike me he doesn't
feel that the slice operation should return something different (e.g.
a tuple).
Kind regards,
Alastair.
--
http://alastairs-place.net
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