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From: Matthew Heaney <matthew_heaney@acm.org>
Subject: Re: Assembler in Ada?
Date: 1999/01/13
Message-ID: <m3iuebjd1p.fsf@mheaney.ni.net>#1/1
X-Deja-AN: 432191825
Sender: matt@mheaney.ni.net
References: <369C5E08.69727537@mbox5.swipnet.se>
NNTP-Posting-Date: Wed, 13 Jan 1999 09:28:38 PDT
Newsgroups: comp.lang.ada
Date: 1999-01-13T00:00:00+00:00
List-Id: <comp.lang.ada>

Thomas Larsson <thomas.larsson@mbox5.swipnet.se> writes:

> I would like to write some assembler into my Ada program (to change
> video mode, use mouse etc).
> 
> How do I do that? (I have tried to figured out how, but I can't)
> Can I do it in a way similar to assembler in C or Pascal?
> eg: _asm {
>               mov cx,100
>       LP:     loop LP
>       }
> 
> I would appreciate a small example program.
> 
> Thanks for your help
> Thomas
> 
> PS. I do the programming in Win98, not UNIX

Read RM95 13.8.

Which compiler are you using?  There should be a section of the manual
called "machine code insertions," or something like that.  Start there.  

Here's an excerpt from the GNAT reference manual, the section titled
Machine Code Insertions:

(start of excerpt)
   Package `Machine_Code' provides machine code support as described in
the Ada 95 Reference Manual in two separate forms:
   * Machine code statements, consisting of qualified expressions that
     fit the requirements of RM section 13.8.

   * An intrinsic callable procedure, providing an alternative
     mechanism of including machine instructions in a subprogram.

   The two features are similar, and both closely related to the
mechanism provided by the asm instruction in the GNU C cmpiler. Full
understanding and use of the facilities in this package requires
understanding the asm instruction as described in `Using and Porting
GNU CC' by Richard Stallman.  Calls to the function `Asm' and the
procedure `Asm' have identical semantic restrictions and effects as
described below.  Both are provided so that the procedure call can be
used as a statement, and the function call can be used to form a
code_statement.

   The first example given in the GNU CC documentation is the C `asm'
instruction:
        asm ("fsinx %1 %0" : "=f" (result) : "f" (angle));

The equivalent can be written for GNAT as:

        Asm ("fsinx %1 %0",
             My_Float'Asm_Output ("=f", result),
             My_Float'Asm_Input  ("f",  angle));
(end of excerpt)
-- 
Those who believe in the supernatural should be required to learn
computer programming.  This would force them to discover that things
which appear at first to be completely mysterious and incomprehensible,
in fact have a logical (and usually simple) explanation.  --J.B.R. Yant