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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: How do I write directly to a memory address?
Date: Mon, 7 Feb 2011 05:56:21 -0800 (PST)
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Date: 2011-02-07T05:56:21-08:00
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Georg Bauhaus wrote on comp.lang.ada:
> In C, if you write
>
> int foo(const int arg) { arg = 3; }
>
> you will get a compile time error.

I know. So? The point is that the "const" was absent in the function I
had to debug, and had been absent for about 15 years.  Also, not a lot
libX11 or Motif functions have "const" arguments.  This bad style had
a lot of influence on the programmers of 15 years ago whose code I
must now maintain.

In Ada, this bad style is simply not possible. In Ada, "in" really
means "in".

> If you write
>
> int foo(const int* arg) { *arg = 3; }
>
> you will get a compile time error.

I know but bugs are easier to detect because when reviewers see a
pointer argument, they know they have to look out for writes through
the pointer.  Even if the pointer is to a "const", since it is
trivially easy to defeat the const-ness.

> For further ammunition for Verdun style language comparisons,
> see function Ada.Numerics.Discrete_Random.Random.

What does that mean?

> I think there are better arguments.

No.  There was an old (because difficult to reproduce) bug.  I spent
time finding and correcting it.  This bug could not have happened in
Ada.  This argument is the only relevant one to me.

--
Ludovic Brenta.