Prev: Q: Stopping a task running a long simulation
Next: Ensuring postconditions in the face of exceptions
From: Simon Wright on 11 Mar 2010 13:31
Anh Vo <anhvofrcaus(a)gmail.com> writes:

> By the way, why put a hollow
> parenthesis for nothing.

I often get trapped by this in Python. foo() calls the parameterless
subprogram foo, foo is its address.
From: Anh Vo on 11 Mar 2010 13:41
On Mar 11, 10:31 am, Simon Wright <si...(a)pushface.org> wrote:
> Anh Vo <anhvofrc...(a)gmail.com> writes:
> >  By the way, why put a hollow
> > parenthesis for nothing.
>
> I often get trapped by this in Python.  foo() calls the parameterless
> subprogram foo, foo is its address.

It is interesting to know this for a Python newbie like me. Thank you
for your good info.
From: Anh Vo on 11 Mar 2010 15:09
On Mar 11, 11:01 am, Charmed Snark <sn...(a)cogeco.ca> wrote:
> Anh Vo expounded in news:2801d429-d00b-46cb-955a-
> To me, with my heretical C background, the "()" is a strong
> reminder that a method is being "called". In C/C++, the statement
>
>      Obj.Clear;
>
> would quietly compile clean (if Clear turned out to be a data
> member) and do nothing.
>
> I do realize that that sort of hijinx doesn't happen around here.
> But now you hopefully understand my twisted state of mind.
>
> Don't worry-- I will assimilate.
>
Actually, Ada has this notation for ages specially in the tasking
area. Here is a incomplete example.
....
task type Bus_Monitor is
entry Start;
entry Stop;
end Bus_Monitor;
Bus_Mon_Obj : Bus_Monitor;

....
Bus_Monitor.Start;
....

Anh Vo



From: Robert A Duff on 11 Mar 2010 16:40
Pascal Obry <pascal(a)obry.net> writes:

> This is deliberate and was a design decision for unification of access
> to variable and function returning a value:
>
> Is_It_Ok : Boolean;
> function Is_It_Good return Boolean;
>
> Then, from the call side there is no distinction:
>
> if Is_It_Ok then
>
> if Is_It_Good then
>
> It is then possible to replace access to a value by a function without
> having to change the code everywhere.

Well, except here:

Is_It_OK := True; -- OK
Is_It_Good := True; -- Illegal!

;-)

I think I'd prefer the empty parens. I'd buy the uniformity of
reference argument in a pure functional language. But in Ada,
function calls can have side effects, whereas variable reads
cannot, so I think perhaps a syntactic distinction would be
useful.

- Bob
From: Jeffrey R. Carter on 11 Mar 2010 19:16
Robert A Duff wrote:
>
> I think I'd prefer the empty parens. I'd buy the uniformity of
> reference argument in a pure functional language. But in Ada,
> function calls can have side effects, whereas variable reads
> cannot, so I think perhaps a syntactic distinction would be
> useful.

Ada 80 required them. They avoided some ambiguities that Ada has without them.
They were removed in Ada 83 due to widespread dislike.

--
Jeff Carter
"In the frozen land of Nador they were forced to
eat Robin's minstrels, and there was much rejoicing."
Monty Python & the Holy Grail
70
 |  Next  |  Last
Pages: 1 2
Prev: Q: Stopping a task running a long simulation
Next: Ensuring postconditions in the face of exceptions