Re: [Boost-users] [exception] array tags

Subject: Re: [Boost-users] [exception] array tags
From: Diederick C. Niehorster (dcnieho_at_[hidden])
Date: 2009-10-25 03:12:11

Hi Emil and Joel,

Thank you for your valuable suggestions. As you might have noticed I'm
rather new to exceptions (in general and the boost library), this
helped a lot.

Thanks!
Diederick

On Sun, Oct 25, 2009 at 3:06 PM, Emil Dotchevski
<emildotchevski_at_[hidden]> wrote:
> On Sat, Oct 24, 2009 at 9:10 PM, Diederick C. Niehorster
> <dcnieho_at_[hidden]> wrote:
>> Hi,
>>
>> I have another question regarding the exception library. I would like
>> to use the BOOST_THROW_EXCEPTION() macro, but also add some tags of my
>> own at the throw site. How do I do this?
>>
>> How would i rewrite the below?
>> typedef boost::error_info<struct tag_std_range_which,std::string>
>> std_range_which;
>> throw boost::enable_error_info(std::out_of_range("Matrix -=: Inputs do
>> not have same shape")) <<
>> Â  Â  Â  Â  Â  Â std_range_which(Rows()!=M.Rows()? "row" : "col");
>
> I would strongly recommend that you don't add a user message as error
> info. Just add the data the catch site needs to format a message. That
> said...
>
>> Simply doing
>> BOOST_THROW_EXCEPTION(std::out_of_range("Matrix -=: Inputs do not have
>> same shape")) <<
>> Â  Â  Â  Â  Â  Â std_range_which(Rows()!=M.Rows()? "row" : "col");
>> does not work
>
> The problem is that std::out_of_range does not derive from
> boost::exception. This is the precise situation
> boost::enable_error_info is designed for:
>
> BOOST_THROW_EXCEPTION(boost::enable_error_info(std::out_of_range("Matrix
> -=: Inputs do not have same shape")) <<
> std_range_which(Rows()!=M.Rows()? "row" : "col");
>
> Or (if you throw std::out_of_range a lot) just derive from it and
> boost::exception, then you don't need to use enable_error_info:
>
> struct my_out_of_range: virtual std::out_of_range, virtual boost::exception { };
>
> BOOST_THROW_EXCEPTION(my_out_of_range() <<
> std_range_which(Rows()!=M.Rows()? "row" : "col");
>
> Emil Dotchevski
> Reverge Studios, Inc.
> http://www.revergestudios.com/reblog/index.php?n=ReCode
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