The "loop and a half"

[Ben Bacarisse]

ram at zedat.fu-berlin.de (Stefan Ram) writes:

> Steve D'Aprano <steve+python at pearwood.info> writes:
>>For-each loops are MUCH easier to understand, and should be taught first.
>
>   I prefer a bottom-up approach.
>
>   For loops are based on iterators.
>
>   So, "bottom-up" in this case means: iterators should be
>   taught before for-loops.
>
>   But iterators are too abstract to be taught very early.

I think this may be a problem with your style.  From your other
postings, I think you value precision and exactness over broad
understanding, and maybe you teach like that.

I my view, it's possible to explain enough about iterators to understand
a huge range of for loops without having to go into the gory details.  I
find the image of a conjurer pulling knotted hankies out of a hat a good
one -- they may go on forever and you don't know if there is rabbit in
there knotting them and deciding which colour comes next.

>   But I will teach iterators and for loops not much later than
>   while-loop. 
>
>   Maybe this way: Use a while-loop and try-catch to get values
>   from an iterator until exhausted, and then introduce the
>   for-loop as an abbreviation for that.

That sounds very complicated, but I think I favour the other extreme to
you.

-- 
Ben.