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< title > integrating boost exception in existing exception class hierarchies</ title >
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< h1 > Boost Exception</ h1 >
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<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
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< div class = "RenoIncludeDIV" >< div class = "RenoAutoDIV" >< h2 > Integrating Boost Exception in Existing Exception Class Hierarchies</ h2 >
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< p > Some exception hierarchies can not be modified to make boost::< span class = "RenoLink" >< a href = "exception.html" > exception</ a ></ span > a base type. In this case, the < span class = "RenoLink" >< a href = "enable_error_info.html" > enable_error_info</ a ></ span > function template can be used to make exception objects derive from boost::< span class = "RenoLink" >< a href = "exception.html" > exception</ a ></ span > anyway. Here is an example:</ p >
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< pre > #include < < span class = "RenoLink" >< a href = "boost_exception_all_hpp.html" > boost/exception/all.hpp</ a ></ span > >
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#include < stdexcept>
typedef boost::< span class = "RenoLink" >< a href = "error_info.html" > error_info</ a ></ span > < struct tag_std_range_min,size_t> std_range_min;
typedef boost::< span class = "RenoLink" >< a href = "error_info.html" > error_info</ a ></ span > < struct tag_std_range_max,size_t> std_range_max;
typedef boost::< span class = "RenoLink" >< a href = "error_info.html" > error_info</ a ></ span > < struct tag_std_range_index,size_t> std_range_index;
template < class T>
class
my_container
{
public:
size_t size() const;
T const &
operator[]( size_t i ) const
{
if( i > size() )
throw boost::< span class = "RenoLink" >< a href = "enable_error_info.html" > enable_error_info</ a ></ span > (std::range_error("Index out of range")) <<
std_range_min(0) <<
std_range_max(size()) <<
std_range_index(i);
//....
}
};
</ pre >
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< p > The call to < span class = "RenoLink" >< a href = "enable_error_info.html" > enable_error_info</ a ></ span > < T> gets us an object of < i > unspecified type</ i > which is guaranteed to derive from both boost::< span class = "RenoLink" >< a href = "exception.html" > exception</ a ></ span > and T. This makes it possible to use < span class = "RenoLink" >< a href = "exception_operator_shl.html" > operator<< </ a ></ span > to store additional information in the exception object. The exception can be intercepted as T & , so existing exception handling will not break. It can also be intercepted as boost::< span class = "RenoLink" >< a href = "exception.html" > exception</ a ></ span > & , so that < span class = "RenoLink" >< a href = "tutorial_transporting_data.html" > more information can be added to the exception at a later time</ a ></ span > .</ p >
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< h3 > See Also:</ h3 >
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< div class = "RenoPageList" >< a href = "boost-exception.html" > Boost Exception< br />
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</ a >< a href = "motivation.html" > Motivation< br />
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<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
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< small > Copyright (c) 2006-2009 by Emil Dotchevski and Reverge Studios, Inc.< br />
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Distributed under the < a href = "http://www.boost.org/LICENSE_1_0.txt" > Boost Software License, Version 1.0</ a > .</ small >
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