Bug in string.find; was: Re: Proposed PEP: New style indexing,was Re: Bug in slice type

[Robert Kern]

Antoon Pardon wrote:
> Op 2005-08-30, Robert Kern schreef <rkern at ucsd.edu>:
> 
>>Bryan Olson wrote:
>>
>>>     Currently, user-defined classes can implement Python
>>>     subscripting and slicing without implementing Python's len()
>>>     function. In our proposal, the '$' symbol stands for the
>>>     sequence's length, so classes must be able to report their
>>>     length in order for $ to work within their slices and
>>>     indexes.
>>>
>>>     Specifically, to support new-style slicing, a class that
>>>     accepts index or slice arguments to any of:
>>>
>>>         __getitem__
>>>         __setitem__
>>>         __delitem__
>>>         __getslice__
>>>         __setslice__
>>>         __delslice__
>>>
>>>     must also consistently implement:
>>>
>>>         __len__
>>>
>>>     Sane programmers already follow this rule.
>>
>>Incorrect. Some sane programmers have multiple dimensions they need to
>>index.
> 
> I don't see how that contradicts Bryan's statement.
> 
>>  from Numeric import *
>>  A = array([[0, 1], [2, 3], [4, 5]])
>>  A[$-1, $-1]
>>
>>The result of len(A) has nothing to do with the second $.
> 
> But that is irrelevant to the fact wether or not sane
> programmes follow Bryan's stated rule. That the second
> $ has nothing to do with len(A), doesn't contradict
> __len__ has to be implemented nor that sane programers
> already do.

Except that the *consistent* implementation is supposed to support the
interpretation of $. It clearly can't for multiple dimensions.

-- 
Robert Kern
rkern at ucsd.edu

"In the fields of hell where the grass grows high
 Are the graves of dreams allowed to die."
  -- Richard Harter