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From: Dave Poirier <instinc@users.sf.net>
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Subject: 64bit access to an array of 8bit values
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Date: Sun, 03 Mar 2002 09:58:34 -0500
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Date: 2002-03-03T09:58:34-05:00
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I'm trying to modelize a small virtual machine, and I'm stuck on the 
memory model.  I'm defining the memory as an array of 8bit values, so 
that I am able to access every byte individually.  The problem comes 
when I try to access them with other data size, like 16/32/64bit.  GNAT 
simply refuses to do the pointer conversion (yeah, probably a bad habit).

So, what would be a "clean" way to do it?  here's what I tried

------
procedure test is
   type Bit8 is mod 2**8;
   type Bit64 is mod 2**64;
   type Bit8Acc is access Bit8;
   type Bit64Acc is access Bit64;

   type RamRange is range 0 .. 4000;

   Ram : array (RamRange) of aliased Bit8;
   Value : Bit64Acc;

begin
   Value := Ram(0)'Access;
end test;
------

test.adb:14:18: expected type "Bit64Acc" defined at line 6
test.adb:14:18: found type access to "bit8" defined at line 14

and also..
------
procedure test is
   type Bit8 is mod 2**8;
   type Bit64 is mod 2**64;
   type Bit8Acc is access all Bit8;
   type Bit64Acc is access all Bit64;

   type RamRange is range 0 .. 4000;

   Ram : array (RamRange) of aliased Bit8;
   Value : Bit64Acc;

begin
   Value := Bit64Acc(Ram(0)'Access);
end test;
------

test.adb:14:12: argument of conversion cannot be access
test.adb:14:12: use qualified expression instead

I'm just a smooth skinned Ada95 newbie, so don't get too big weapons to 
send replies ;)

Thanks for helping me learn :)
EKS - Dave Poirier