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From: "Robert I. Eachus" <eachus@mitre.org>
Subject: Re: Why Ada is not the Commercial Lang of  Choice
Date: 1997/06/18
Message-ID: <33A7FBFF.29D2@mitre.org>#1/1
X-Deja-AN: 249349904
Organization: The MITRE Corporation
Reply-To: eachus@mitre.org
Newsgroups: comp.lang.ada
Date: 1997-06-18T00:00:00+00:00
List-Id: <comp.lang.ada>


Paul Van Bellinghen writes:
> 
> Claim:
> It is much easier in C, for example, to output a data word to
> an I/O device that is memory mapped.
> 
> Supporting Evidence:
> 1       One need only define a pointer
> 2       and assign it the memory mapped address
> 3       then store the desired data value to the contents of the pointer.
> 
> Example:
>  #define mem_map_addr B0100040
>  unsigned int *p;
> 
>  p = (unsigned int *) mem_map_addr;
> 
>  *p = 0x00344556;
> 
> Claim:
> It is harder to do it in Ada because i write it out in more words.

   Wait a second here.  The eqivalent Ada is:

   Mem_Map: Integer;
   for Mem_Map'Address use 16#B0100040#;
 begin
   Mem_Map := 16#00344556#;

   ...which is a little shorter in terms of characters, words, and
lines.  I could go into the bugs in both the Ada and the C--I'd want
pragma Volitile(Mem_Map); in both Ada and C.  Most compilers will get it
"right" but why take the risk.  Also, it might be necessary to call
System.Storage_Elements.To_Address, but I can't imagine any compiler for
a machine where 16#B01000040# is a meaningful address not allowing
literals for addresses.

-- 


                                               Robert I. Eachus

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