[Edu-sig] "do" as a keyword

[Vern Ceder]

Brian Blais wrote:
> I find that when teaching beginning programmers, they usually think in 
> "until" terms, and not "while" terms.

I haven't noticed that so much myself, actually... My students (grades 
8-10) tend to think in fixed numbers of repetitions and the whole idea 
of a flexible loop is a big jump for some. That may be age/development 
related, though...
> 
> they find the "while" logic to be unintuitive, and I often find myself 
> feeling the same way: crafting it with the until logic, and then 
> reversing it.  Perhaps I should do as above, and do:

I would second Kirby's comment that "intuitive" in programming contexts 
often means "what we're used to" or even "the way I do it". ;-)

> while True:
>     Forward()
>     if Touched(): break
> 
> but somehow that feels wrong to me, like bypassing the point of the 
> while: all that power to check for conditions, and you just use it to 
> check True, and then use a break inside.  It's readable, I guess, but 
> not a programming construct I am immediately drawn to.

I agree with you here... except for event loops, where the while True: 
syntax is exactly what you need.

Again, I'm with Kirby on Python's parsimony in control structures. A 
repeat 0 to x times structure is more general than a repeat 1 to x times 
structure, and having a special case for the latter wouldn't be 
"Pythonic" as I grok the term...

Cheers,
Vern

-- 
This time for sure!
    -Bullwinkle J. Moose
-----------------------------
Vern Ceder, Director of Technology
Canterbury School, 3210 Smith Road, Ft Wayne, IN 46804
vceder at canterburyschool.org; 260-436-0746; FAX: 260-436-5137