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From: Ken Garlington <Kennie.E.Garlington@lmco.com>
Subject: Re: Why Ada is not the Commercial Lang of Choice
Date: 1997/06/18
Message-ID: <33A83DA9.67E@lmco.com>#1/1
X-Deja-AN: 249393410
References: <33a1c14d.155787285@news.mhv.net>
 <5o5hv9$dcd$1@goanna.cs.rmit.edu.au>
Organization: Lockheed Martin Tactical Aircraft Systems
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.

In Ada, something like:

   Memory_Mapped_Address : constant := 16#0100040#;

   Memory_Mapped_Value : Interfaces.C.unsigned; -- just to keep type
compatibility
   for Memory_Mapped_Value'Address use Memory_Mapped_Address;

   Memory_Mapped_Value := 16#00344556#;

And the neat thing is, Memory_Mapped_Value will always be mapped to the
area of memory you want! No worries about your pointer being corrupted
--
because there isn't a pointer! Who knows, now that the compiler knows
that the address is fixed, you might even get more efficient code!

> 
> Example:
>  #define mem_map_addr B0100040
>  unsigned int *p;
> 
>  p = (unsigned int *) mem_map_addr;
> 
>  *p = 0x00344556;

Claim: The Ada does the same thing, in the same number of lines, and it
does it
more safety, more clearly, and (gasp) possibly more efficiently!

--
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