[Python-checkins] CVS: python/dist/src/Lib string.py,1.46,1.47

[Skip Montanaro]

    bjorn> Exactly. Strings can't possibly know enough about all possible
    bjorn> sequence types, including user defined ones, to make this
    bjorn> efficient.

Why not?  All "xyz".join needs to know is how to index into a sequence with
__getitem__ using an ever increasing integer series that begins at 0...

    bjorn> Which is (a) a good argument for implementing join in the
    bjorn> sequence types, since there are much more than *two* sequence
    bjorn> types <wink> and (b) suggests that we really need a common base
    bjorn> class for the sequence types to share common functionality
    bjorn> (Python is an OO language after all...)

All sequence types know about __getitem__ (otherwise they wouldn't be
sequences).  Conversely, you are asking that all sequences know enough about
strings (and eventually Unicode) to perform join, *and* you're asking the
same algorithm to be replicated in all sequences. (Will a join method
eventually be required for an object to be considered a sequence?)

    bjorn> Conversely, to you really think that both string classes should
    bjorn> know how to efficiently join all possible sequence types?

Again, knowing how to count using integers and call __getitem__ is all that
is required.

    bjorn> sometimes implementing join as a series of concatenations does
    bjorn> work, and is much easer than trying to implement __getitem__.

If it doesn't implement __getitem__, I don't think you can honestly call it
a sequence...

Skip Montanaro | http://www.mojam.com/
skip at mojam.com | http://www.musi-cal.com/
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