terminological obscurity

[Grant Edwards]

In article <mailman.145.1085158045.6949.python-list at python.org>, Michael Chermside wrote:

>> All tuple methods are also list methods, and most list methods
>> are also tuple methods; among those that are NOT also tuple
>> methods, there are exactly two ('count' and 'index') that do
>> not involve mutation. Is there any special reason why they
>> AREN'T also tuple methods?
> 
> Yes. Both make sense only if you consider a tuple as a homogeneous
> sequence of items, and that's not what Guido intended it to be
> used for.

I'm sure I'm being dim, but I don't understand what homogeneity
has to do with it.

For example, why shouldn't index() find an object in a
non-homogeneous sequence? Either the object is in the sequence or
it's not. If it is, there is an index that corresponds to it.

The relationship

 (a,b,c,d,e)[3] is d

is true regardless of the types of a,b,c and e.

I can maybe see why not supporting sort() or reduce() on a
non-homogeneous sequence makes sense if one was of the opinion
that it should be illegal to use a binary operator on two
objects whose types differ, but I don't see why either count()
or index() should have anything to do with homogeneity, since
it pretty much has to be OK to use "is" or "==" on objects of
differing types.

-- 
Grant Edwards                   grante             Yow!  Am I accompanied by
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