Re: Pascal to ADA

["Steve" <nospam_steved94@comcast.net>]

This is as close as I can come to a literal translation:

  subtype BYTE is Unsigned_8;
  subtype LONGINT is Integer;
  subtype WORD is Unsigned_16;

  procedure Add32(N:LONGINT;M:LONGINT;R: in out LONGINT) is
    N_As_Bytes : array(0..3) of BYTE;
    for N_As_Bytes'Address use N'Address;
    M_As_Bytes : array(0..3) of BYTE;
    for M_As_Bytes'Address use M'Address;
    R_As_Bytes : array(0..3) of BYTE;
    for R_As_Bytes'Address use R'Address;
    B : WORD;
    C : WORD;-- Carry
  begin
    R := 0 ;
    C := 0 ;
    for A in 0 .. 3 loop
      B := WORD( N_As_Bytes(A) + M_As_Bytes(A) ) + C ;
      R_As_Bytes(A) := BYTE( B and 16#FF# );
      C := Shift_Right( B, 8 );
    end loop;
  end Add32;

You'll need to have "with Interfaces; use Interfaces" included in order to
define Unsigned_8 and Unsigned_16.

I changed _N to N_As_Bytes since Ada does not permit using an underscore as
the first character in an identifier.

Steve
(The Duck)


"Tilman Gloetzner" <tilman.gloetzner@etas.co.kr> wrote in message
news:bpa46j$o0l$1@news1.kornet.net...
> Hello,
>
> 1) what is a effecient way of rewriting the following code fragement in
ADA
> ?  With the absolute keyword, Pascal  effectively casts
> N, M, and R from a 4 byte integer type to an array of 4 bytes by an
address
> access.  I guess to implement the same mechanism in
> ADA is not in line with ADA's philosophy.
>
> 2) How do I mask out bits in a (unsigned) number type, as logical
operators
> work only on booleans ?
>
> Thank you,
>
> Tilman
>
> ----------------------------------------------------------------
> PROCEDURE Add32(N:LONGINT;M:LONGINT;VAR R:LONGINT) ;
> VAR
>      _N : ARRAY[0..3] OF BYTE ABSOLUTE N ;
>      _M : ARRAY[0..3] OF BYTE ABSOLUTE M ;
>      _R : ARRAY[0..3] OF BYTE ABSOLUTE R ;
>      A  : BYTE ;
>      B  : WORD ;
>      C  : WORD ; { Carry }
> BEGIN
>      R := 0 ;
>      C := 0 ;
>      FOR A := 0 TO 3 DO BEGIN
>          B := _N[A] + _M[A] + C ;
>          _R[A] := B AND $FF ;
>          C := B SHR 8 ;
>      END ;
> END  ;
>
>