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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Exceptions
Date: Sun, 09 Dec 2007 16:39:44 -0500
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2007-12-09T16:39:44-05:00
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tmoran@acm.org writes:

>>Is there any way to force programmers to catch exception that
>>your function throws?
>   Do you mean force them to write code like:
> begin
>   y := func(x);
> exception
>   when funcs_important_exception=>null; -- ignore unimportant exception
> end;

I've heard that this is a common problem in Java code.
Compiler complains, so the programmer puts in an
exception-ignoring handler -- probably without any
comment explaining why.

But I don't get it.  If you think a certain exception
is impossible in a certain case, and the compiler
insists on a handler, the obvious thing to do
is raise an unchecked exception.  In Ada:

    when Funcs_Important_Exception =>
        -- <comment explaining why this can never happen>
        raise Program_Error;

Why on earth would anybody write "null;" there?!

I don't blame the Java language design for this problem.

- Bob