Re: Local vs global variables in ADA

[Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov>]

Robert A Duff <bobduff@shell01.TheWorld.com> writes:

> Stephen Leake <stephen.a.leake.1@gsfc.nasa.gov> writes:
> 
> > Never use a "while" loop. Mostly because "exit when" is much clearer,
> > partly because I've used other languages that had slightly different
> > definitions of "while", and I can't keep them straight.
> 
> Like what?  I mean, which languages have different definitions of
> "while" loops, and what are the differences.  I thought "while" loops
> were one of the few cases where there is pretty much agreement on the
> semantics across languages.

I had hoped someone else would actually answer your question, but they
didn't. 

At the moment, I only use Ada and C, so I don't really remember what
the issues are precisely.

What I do remember is being confused about whether the loop body
executes once for a "false" while condition. Especially when the
"while" is at the end.

I believe different languages (I've used Pascal, C, COBOL, Fortran,
lisp, Ada) do this differently. But I could be wrong; it could be that
I could just never remember the (common) rule.

Hmm. Checking my ANSI C manual, I see that if "while" is at the top,
the loop body is not executed if the condition is false. If "while" is
at the bottom, the loop body is executed once if the condition is
false.

Ada only allows "while" at the top, and it has the same rule as C.

Anyway, I see no reason to strain my limited supply of brain cells
trying to remember this, when loop/exit/end loop covers all the cases,
and is perfectly clear.

-- 
-- Stephe