Re: Pascal program file parameter to Ada translation (Was: Re: Is GPC dead?)

Hi Kevan,

>      huge : Integer := 128_000_000;

> Here the size of the array is predefined with a constant "huge".

No. "huge" is a variable that is initialised to 128,000,000. The memory is
allocated dynamicly and it is allocated from the heap (the main memory
pool).

Perhaps this is a better example for what you want

with Ada.Text_IO;  use Ada.Text_IO;
with Ada.Unchecked_Deallocation;

procedure Foo is

   package Integer_IO is new Ada.Text_IO.Integer_IO (Integer);  use
Integer_IO;

   type vector     is array (Integer range <>) of Float;
   type vector_ptr is access vector;
   procedure Free_Vector is new Ada.Unchecked_Deallocation (vector,
vector_ptr);

   num : Integer;

begin

   get (num);  -- read the size of the array from standard input

   declare

      xg_ptr : vector_ptr := new vector (0..num);
      xg     : vector renames xg_ptr.all;

   begin
      Put (xg'last);
      New_line;
      Free_Vector (xg_ptr);  -- essential to avoid memory leaks
   end;

end Foo;

And another example,

with Ada.Text_IO;  use Ada.Text_IO;
with Ada.Unchecked_Deallocation;

procedure Foo is

   package Integer_IO is new Ada.Text_IO.Integer_IO (Integer);  use
Integer_IO;

   type vector     is array (Integer range <>) of Float;
   type vector_ptr is access vector;
   procedure Free_Vector is new Ada.Unchecked_Deallocation (vector,
vector_ptr);

   min, max : Integer;

   procedure bahbah (min,max : Integer) is
      xg_ptr : vector_ptr := new vector (min..max); -- min, max unknown at
compile time
      xg     : vector renames xg_ptr.all;
   begin

      Put (xg'last);
      New_line;
      Free_Vector (xg_ptr);  -- essential to avoid memory leaks

   end bahbah;

begin

   get (min);
   get (max);

   bahbah (min,max);

end Foo;

Cheers,
Leo


On 6 January 2017 at 04:39, Kevan Hashemi <[email protected]> wrote:

> Leo: Thank you for your code example.
>
>    for i in 10 .. 20 loop
>>       -- create xg on the stack (okay but stack size is limited)
>>       -- xg exists only within this declare block
>>       declare
>>          xg : Array (0..i-1) of Float;
>>       begin
>>          Put (xg'last);
>>          New_line;
>>       end;
>>    end loop;
>>
>
> That's the dynamic allocation I'm looking for, except it's on the stack. I
> need to use the main memory for dynamic allocation.
>
>       huge : Integer := 128_000_000;
>>       xg_ptr : vector_ptr := new vector (0..huge);
>>       xg     : vector renames xg_ptr.all;
>>    begin
>>       Put (xg'last);
>>       New_line;
>>       Free_Vector (xg_ptr);  -- essential to avoid memory leaks
>>    end;
>>
>
> Here the size of the array is predefined with a constant "huge".
>
> Bastiaan: Thanks for the link. In the linked code we have:
>
> >   VA     := new Vector (1 .. 10);
> >   VB     := VA;  -- points to the same location as VA
>
> Here, the vector size is predefined with the constants 1 and 10.
>
> Peter: Thank you for your FPC example, which does exactly what I need.
>
> > program A;
> > type
> > graph_type = array of real;
> > var
> >   xg:graph_type;
> >   i:integer;
> > begin
> >   for i:=100 to 200 do
> >   begin
> >     setlength(xg,i);
> >     xg := nil;
> >   end;
> > end.
>
> Somehow, I missed setlength when I looked into FPC, and when I asked the
> FPC group about dynamic arrays, they must have interpreted my question as
> "does FPC support exactly the same syntax as GPC". So it looks like I could
> switch to FPC with minimal work.
>
>
> Yours, Kevan
>
>
> --
> Kevan Hashemi, Electrical Engineer
> Physics Department, Brandeis University
> http://alignment.hep.brandeis.edu/
>

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