question about functions (bis)

question about functions (bis)

[Pascal LEJEUNE]

Hello everybody,

Thank you for your replies !!!!
What I want to do, is to give my user the possibility of operators
to a type (for example C := A + B, C := A - B, C := A < B ...). This
type is not very complex (a record of 4 bytes).
Then, my operator is a rename of a function, for example :
function "+" (A, B : in T) return T renames ADD;

Finaly, my function ADD use a hardware component which do
the operation with the addresses (it's an asic which needs
to know on which variable the operation is done) :

function ADD (A, B : in T) return T is
   tmp : system.address;
begin
   << find the address of the result (that's my problem !!) >> and
   put it in a local variable (tmp)

   call a procedure which use directly the hardware :
   proc (a'address, b'address, tmp);
end ADD;

So, the problem is quite simple : the type T is a "numerical" type
on which it is normal to have operators ... but the hardware need
to have the address of the arguments and the address of the result !!!

I hope i'll find a "nice" solution (ie in Ada or C), but if it is
impossible,
i'll use ASM !


Thank you !!!


Pascal LEJEUNE

Re: question about functions (bis)

[Philip Anderson]

Pascal LEJEUNE wrote:
> 
> function ADD (A, B : in T) return T is
>    tmp : system.address;
> begin
>    << find the address of the result (that's my problem !!) >> and
>    put it in a local variable (tmp)
> 
>    call a procedure which use directly the hardware :
>    proc (a'address, b'address, tmp);
> end ADD;
> 
> So, the problem is quite simple : the type T is a "numerical" type
> on which it is normal to have operators ... but the hardware need
> to have the address of the arguments and the address of the result !!!


Can't you simply write:
 
function ADD (A, B : in T) return T is
   tmp : T;
begin
   -- call a procedure which directly uses the hardware :
   --
   proc (a'address, b'address, tmp'address);
   return tmp;
end ADD;


-- 
hwyl/cheers,
Philip Anderson
Alenia Marconi Systems
Cwmbr�n, Cymru/Wales

Re: question about functions (bis)

[Jeff Creem]

Philip Anderson <phil.anderson@gecm.com> wrote in message
news:38883285.AB6ED64C@gecm.com...
> Pascal LEJEUNE wrote:
> >
> > function ADD (A, B : in T) return T is
> >    tmp : system.address;
> > begin
> >    << find the address of the result (that's my problem !!) >> and
> >    put it in a local variable (tmp)
> >
> >    call a procedure which use directly the hardware :
> >    proc (a'address, b'address, tmp);
> > end ADD;
> >
> > So, the problem is quite simple : the type T is a "numerical" type
> > on which it is normal to have operators ... but the hardware need
> > to have the address of the arguments and the address of the result !!!
>
>
> Can't you simply write:
>
> function ADD (A, B : in T) return T is
>    tmp : T;
> begin
>    -- call a procedure which directly uses the hardware :
>    --
>    proc (a'address, b'address, tmp'address);
>    return tmp;
> end ADD;
>



Which by the way when you do this, in certain cases, GNAT actually does not
even really create a new
variable tmp. In certain instances tmp is optimized out and 'address tmp =
'address of location of return
value.

(At least it looked that way to me compiling some test code on x86 and
looking at resulting code)
Jeff Creem

Re: question about functions (bis)

[David C. Hoos, Sr.]

Pascal LEJEUNE <pascal.lejeune@matra-transport.fr> wrote in message
news:8690s0$8tq$1@news.mgn.net...
> Hello everybody,
>
> Thank you for your replies !!!!
> What I want to do, is to give my user the possibility of operators
> to a type (for example C := A + B, C := A - B, C := A < B ...). This
> type is not very complex (a record of 4 bytes).
> Then, my operator is a rename of a function, for example :
> function "+" (A, B : in T) return T renames ADD;
>
> Finaly, my function ADD use a hardware component which do
> the operation with the addresses (it's an asic which needs
> to know on which variable the operation is done) :
>
> function ADD (A, B : in T) return T is
>    tmp : system.address;
> begin
>    << find the address of the result (that's my problem !!) >> and
>    put it in a local variable (tmp)
>
>    call a procedure which use directly the hardware :
>    proc (a'address, b'address, tmp);
> end ADD;
>
> So, the problem is quite simple : the type T is a "numerical" type
> on which it is normal to have operators ... but the hardware need
> to have the address of the arguments and the address of the result !!!
>
> I hope i'll find a "nice" solution (ie in Ada or C), but if it is
> impossible,
> i'll use ASM !
Why don't you declare a local variable for the result, then after the
hardware has done its job, return the value of the result to the caller,
say, as follows:

function ADD (A, B : in T) return T is
   tmp : T;
begin
   call a procedure which use directly the hardware :
   proc (a'address, b'address, tmp'address);
   return tmp;
end ADD;

Re: question about functions (bis)

[Nick Roberts]

The 'nice' solution is simple: declare a temporary of the return type, pass
its address to the hardware, and return it at the end of the function.

   function Add (Left, Right: in T) return T is
      Result: T;
   begin
      ASIC_Add(Left'Address,Right'Address,Result'Address);
      return Result;
   end;

   pragma Inline(Add);

Couldn't be easier!

Note the use of a 'pragma Inline' to (hopefully) help with speed (which I
presume matters in this situation). With a bit of luck, the compiler will
optimise reasonably.

--
Nick Roberts
http://www.adapower.com/lab/adaos

"Pascal LEJEUNE" <pascal.lejeune@matra-transport.fr> wrote in message
news:8690s0$8tq$1@news.mgn.net...
> ...
> Finaly, my function ADD use a hardware component which do
> the operation with the addresses (it's an asic which needs
> to know on which variable the operation is done) :
>
> function ADD (A, B : in T) return T is
>    tmp : system.address;
> begin
>    << find the address of the result (that's my problem !!) >> and
>    put it in a local variable (tmp)
>
>    call a procedure which use directly the hardware :
>    proc (a'address, b'address, tmp);
> end ADD;
>
> So, the problem is quite simple : the type T is a "numerical" type
> on which it is normal to have operators ... but the hardware need
> to have the address of the arguments and the address of the result !!!