Re: Ada.Execution_Time

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 12/13/2010 03:25 PM, Randy Brukardt wrote:
>
> The logic is that you need a "null;" statement when there is nothing in some
> list of statements. A pragma (or label) is not "nothing", so the requirement
> for "null;" is illogical in those cases.

The logic I recall from watching videos of Ichbiah, Barnes, and Firth presenting 
Ada (80) at the Ada Launch was that a null statement indicates that the sequence 
of statements (SOS) was intentionally null; it was contrasted to the single 
semicolon used for the null statement in some other languages, which is easily 
missed when reading, easily accidentally deleted when editing, and generally 
considered a Bad Thing. Another justification is that it prevents the reader 
from wondering if something was accidentally deleted.

As such, a pragma might be "something" and as such not require a null statement, 
but I would disagree about a label. A label by itself would make me wonder what 
happened to the statement it labels.

Given the argument that the null statement is needed when there is no other SOS, 
that SOS refers to executable statements, and that neither a pragma nor a label 
are considered such, I would guess this is contrary to the intention of the 
original language designers.

I so like the idea that something explicit is required when a region 
deliberately contains nothing that I'd like to see "null;" as a declaration that 
is required when a declarative region contains nothing else.

-- 
Jeff Carter
"He didn't get that nose from playing ping-pong."
Never Give a Sucker an Even Break
110