Strange range

[Terry Reedy]

On 4/1/2016 4:14 PM, Marko Rauhamaa wrote:

> There's a bit of a cognitive dissonance between iterables and iterators.
> On the one hand, they behave identically in many contexts.

Because iterators *are* (a proper subset of) iterables  This goes back 
to pre-iterator days when for-loops worked on sequences and 
sequence-like objects.  When iterators (and generators and generator 
functions) were added and the iteration protocol added to the sequence 
protocol, 'sequence' was generalized to 'iterable'.  Replacing 
'sequence' with 'iterator' (and having an iterator not be an iterable) 
would have broken most code and made for loops less convenient to use.

> On the other hand, the distinction

between iterators and non-iterator iterables

> is crucial in some special cases.

I often call non-iterator iterables 're-iterables' (which is usually 
correct) but there is no agree-on term.  It is sort of like having 
'people' and 'men' but no word for non-men people.

> (Somehow, the difference between iterables and iterators is analogous
> with the difference between C's arrays and pointers.)

(Yes, C uses pointers to iterates through arrays, in either direction.)

-- 
Terry Jan Reedy