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From: Robert Dewar <robert_dewar@my-deja.com>
Newsgroups: comp.lang.ada
Subject: Re: Ok sorry, it is just a book gives no feedback.
Date: Thu, 04 Jan 2001 17:09:04 GMT
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Date: 2001-01-04T17:09:04+00:00
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In article <932632$e0e$1@nnrp1.deja.com>,
  n_brunot@my-deja.com wrote:
> Just look the following code (simplified from old buggy
code).
> Depending if the compiler evaluate right or left term first
for "&",
> you get quite different behavior ....
> This is a pathologic case, but good example to show why it's
not so bad
> to avoid side effect each time you can, and keep constantly
testing your
> code on different Ada compilers ...
>
> with Text_Io;
> procedure Test is
>    N : Natural := 10;
>    function Decrement return String is
>    begin
>       N := N - 1;
>       return "A";
>    end;
>    function Recursive return String is
>    begin
>       if N /= 0 then
>          return Decrement & Recursive;
>       else
>          return "A";
>       end if;
>    end;
> begin
>    Text_Io.Put_Line (Recursive);
> end;

This would be horrible code even if procedures were used.
Global variables in general are harmful if not very carefully
used.

You argue that functions should not have side effects, and then
use as an example a very poorly written junk function. The
point is that there are plenty of legitimate functions that
have side effects in the sense in which they were defined
here.

E.g. A function that takes two pointers to strings and returns
a pointer to their concatenation is quite reasonable, but has
side effects according to this definition.

Note that ANY allocation has a side effect, so these rules
about
functions would say that no functions can ever do allocations.
That's an unreasonable restriction!


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