Re: Local vs global variables in ADA

[claveman@grzorgenplatz.net (Charles H. Sampson)]

Fraser Wilson <newsfraser@blancolioni.org> wrote:

> Jeffrey Carter <jrcarter@acm.org> writes:
> 
> > True. But since at the Ada launch on 1980 Dec 10, some of those people
> > said that the language contained "goto" primarily to facilitate 
> > automated translation from languages such as FORTRAN 66, and "while"
> > primarily to facilitate such translation from languages such as Pascal,
> 
> On the "while" comment: are you (or were they) referring to the fact
> that a while loop can be expressed as a loop/exit when/end loop
> construction, or is there something about while loops that should be
> avoided?  Isn't there a preference hierarchy from for loop to while
> loop to loop?  I.e. use a for loop whenever possible, failing that a
> while loop, and as a last resort a loop with an exit.  OK, and as a
> last last resort use a goto.
> 
> Fraser.

     I don't know what the "founders" intended but how's this for a
rule: Use a for-loop only when it's appropriate, use a while-loop only
when it's appropriate, use an "infinite" loop in all other cases. :-)

     Seriously, here's what I try to do: use the for-loop and while-loop
only when they express the loop's termination condition.  In other
words, do not use exit statements within loops of these forms; if a loop
requires an exit statement, then use an "infinite" loop instead.
Unfortunately, my will power is often too weak to overcome the
convenience of the automatically declared counting variable of a
for-loop.  I'm much better with while loops.

                                Charlie

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