September 2007 - Boost - lists.preview.boost.org

[utility/swap]Call for testing/comments
by Joseph Gauterin 03 Oct '07

03 Oct '07

As discussed previously on the mailing list with David Abrahams and Steve Watanabe, I've written a swap function for boost which uses argument dependent lookup (aka koenig lookup), encapsulating the idiom: using std::swap; swap(a,b); It can currently be found at 'http://www.josephgauterin.myzen.co.uk/swap.zip' as I don't have SVN write access. Currently, I only have access to MSVC8.0 - I'd be grateful if people with access to other compilers could test this (bjam in the test directory), in paticular I believe it may not work correctly with gcc < 3.2 and MSVC6.0. I'd also be grateful for any comments or constructive criticism.

4 5

Re: [boost] [Boost] [iterator][utility] advance() and distance() for new iterator concepts (Was: [Boost-users] std::distance ignores random_access_traversal_tag)
by Sebastian Redl 03 Oct '07

03 Oct '07

Hi, Just realized the previous patch used tabs instead of spaces. This one fixes that. Sebastian Redl Index: boost/next_prior.hpp =================================================================== --- boost/next_prior.hpp (revision 39574) +++ boost/next_prior.hpp (working copy) @@ -8,11 +8,12 @@ // Revision History // 13 Dec 2003 Added next(x, n) and prior(x, n) (Daniel Walker) +// 26 Sep 2007 Made next(x, n) and prior(x, n) use Boost. (Sebastian Redl) #ifndef BOOST_NEXT_PRIOR_HPP_INCLUDED #define BOOST_NEXT_PRIOR_HPP_INCLUDED -#include <iterator> +#include <boost/utility/iterator.hpp> namespace boost { @@ -32,7 +33,7 @@ template <class T, class Distance> inline T next(T x, Distance n) { - std::advance(x, n); + boost::advance(x, n); return x; } @@ -42,7 +43,7 @@ template <class T, class Distance> inline T prior(T x, Distance n) { - std::advance(x, -n); + boost::advance(x, -n); return x; } Index: boost/utility/iterator.hpp =================================================================== --- boost/utility/iterator.hpp (revision 0) +++ boost/utility/iterator.hpp (revision 0) @@ -0,0 +1,40 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +#ifndef BOOST_UTILITY_ITERATOR_HPP_SR_H +#define BOOST_UTILITY_ITERATOR_HPP_SR_H + +#include <boost/iterator/iterator_categories.hpp> + +#include <boost/utility/detail/iterator_dispatch.hpp> + +namespace boost +{ + // A replacement for std::advance that uses the new iterator categories. + template <class IncrementableIterator, class Distance> + inline void advance(IncrementableIterator &i, Distance n) + { + typedef BOOST_DEDUCED_TYPENAME boost::iterator_traversal< + IncrementableIterator + >::type traversal; + detail::advance(traversal(), i, n); + } + + // A replacement for std::distance that uses the new iterator categories. + template <class SinglePassIterator> + inline BOOST_DEDUCED_TYPENAME std::iterator_traits< + SinglePassIterator>::difference_type + distance(SinglePassIterator first, + SinglePassIterator last) + { + typedef BOOST_DEDUCED_TYPENAME boost::iterator_traversal< + SinglePassIterator + >::type traversal; + return detail::distance(traversal(), first, last); + } +} + +#endif Index: boost/utility/detail/iterator_dispatch.hpp =================================================================== --- boost/utility/detail/iterator_dispatch.hpp (revision 0) +++ boost/utility/detail/iterator_dispatch.hpp (revision 0) @@ -0,0 +1,124 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +#ifndef BOOST_UTILITY_DETAIL_ITERATOR_DISPATCH_HPP_SR_H +#define BOOST_UTILITY_DETAIL_ITERATOR_DISPATCH_HPP_SR_H + +#include <boost/iterator/iterator_categories.hpp> +#include <boost/iterator/iterator_concepts.hpp> + +namespace boost +{ + namespace detail + { + // For incrementable, single-pass and forward traversable iterators: + // use the classic version, because that's the basic feature set anyway. + template <class IncrementableIterator, class Distance> + inline void advance(boost::incrementable_traversal_tag, + IncrementableIterator &i, Distance n) + { + boost::function_requires< + boost_concepts::IncrementableIterator< + IncrementableIterator + > + >(); + + while(n > 0) { + ++i; + --n; + } + } + + // Bi-directional iterators use this version. Negative distances are + // allowed. + template <class BidirectionalTraversalIterator, class Distance> + inline void advance(boost::bidirectional_traversal_tag, + BidirectionalTraversalIterator &i, Distance n) + { + boost::function_requires< + boost_concepts::BidirectionalTraversal< + BidirectionalTraversalIterator + > + >(); + + if(n > 0) { + while(n) { + ++i; + --n; + } + } else { + while(n) { + --i; + ++n; + } + } + } + + // Random-access traversal iterators get the shortcut. + template <class RandomAccessTraversalIterator, class Distance> + inline void advance(boost::random_access_traversal_tag, + RandomAccessTraversalIterator &i, Distance n) + { + boost::function_requires< + boost_concepts::RandomAccessTraversal< + RandomAccessTraversalIterator + > + >(); + + i += n; + } + + // Incrementable iterators cannot have their distance taken, since it is + // not possible to hold two valid iterators to different parts of a + // sequence; nor could they be compared. + + // This version is for single-pass, forward and bi-directional traversal + // iterators. The use cases for single-pass iterators are limited, but + // it can, for example, be used to determine the number of elements + // that can be extracted from an input stream iterator. + template <class SinglePassIterator> + inline BOOST_DEDUCED_TYPENAME std::iterator_traits< + SinglePassIterator>::difference_type + distance(boost::single_pass_traversal_tag, + SinglePassIterator first, + SinglePassIterator last) + { + boost::function_requires< + boost_concepts::SinglePassIterator< + SinglePassIterator + > + >(); + + BOOST_DEDUCED_TYPENAME std::iterator_traits< + SinglePassIterator>::difference_type dist = 0; + while(first != last) { + ++dist; + ++first; + } + return dist; + } + + + // Random-access traversal iterators get the shortcut. + template <class RandomAccessTraversalIterator> + inline BOOST_DEDUCED_TYPENAME std::iterator_traits< + RandomAccessTraversalIterator>::difference_type + distance(boost::random_access_traversal_tag, + RandomAccessTraversalIterator first, + RandomAccessTraversalIterator last) + { + boost::function_requires< + boost_concepts::RandomAccessTraversal< + RandomAccessTraversalIterator + > + >(); + + return last - first; + } + } +} + +#endif Index: boost/utility.hpp =================================================================== --- boost/utility.hpp (revision 39574) +++ boost/utility.hpp (working copy) @@ -12,6 +12,7 @@ #include <boost/utility/addressof.hpp> #include <boost/utility/base_from_member.hpp> #include <boost/utility/enable_if.hpp> +#include <boost/utility/iterator.hpp> #include <boost/checked_delete.hpp> #include <boost/next_prior.hpp> #include <boost/noncopyable.hpp> Index: libs/utility/utility.htm =================================================================== --- libs/utility/utility.htm (revision 39574) +++ libs/utility/utility.htm (working copy) @@ -17,6 +17,8 @@ Function templates <a href="#checked_delete">checked_delete() and checked_array_delete()</a></li> <li> + Function templates <a href="#functions_advance_distance">advance() and distance()</a></li> + <li> Function templates <a href="#functions_next_prior">next() and prior()</a></li> <li> Class <a href="#Class_noncopyable">noncopyable</a></li> @@ -30,6 +32,19 @@ checked_array_delete()</h2> <p>See <a href="checked_delete.html">separate documentation</a>.</p> <h2> + <a name="functions_advance_distance">Function</a> templates advance() and distance()</h2> + <p>The advance() and distance() functions provide the exact functionality of their standard library counterparts, but use the Boost.Iterators traversal category to decide on the correct implementation. This means, for example, that they work in constant time for vector<bool> iterators instead of linear time (provided that the iterator is correctly tagged).</p> + <blockquote> + <pre>template <class IncrementableIterator, class Distance> +void advance(IncrementableIterator &it, Distance n); + +template <class SinglePassIterator> +typename std::iterator_traits<SinglePassIterator>::difference_type +distance(SinglePassIterator first, SinglePassIterator last);</pre> + </blockquote> + <p>See the implementation of next() and prior() below to see a usage example.</p> + <p>You can include the header <boost/utility/iterator.hpp> directly to obtain these functions without the other utilities.</p> + <h2> <a name="functions_next_prior">Function</a> templates next() and prior()</h2> <p>Certain data types, such as the C++ Standard Library's forward and bidirectional iterators, do not provide addition and subtraction via operator+() or @@ -45,7 +60,7 @@ template <class T, class Distance> T next(T x, Distance n) { - std::advance(x, n); + boost::advance(x, n); return x; } @@ -55,7 +70,7 @@ template <class T, class Distance> T prior(T x, Distance n) { - std::advance(x, -n); + boost::advance(x, -n); return x; }</pre> </blockquote> Index: libs/utility/test/adv_ra_run.cpp =================================================================== --- libs/utility/test/adv_ra_run.cpp (revision 0) +++ libs/utility/test/adv_ra_run.cpp (revision 0) @@ -0,0 +1,26 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that advance() works for random access traversal iterators. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( advance_random_access ) +{ + mock_iterator<boost::random_access_traversal_tag> it; + boost::advance(it, 5); + boost::advance(it, -3); + BOOST_CHECK_EQUAL(*it, 2); + BOOST_CHECK_EQUAL(it.increment_calls(), 0); + BOOST_CHECK_EQUAL(it.decrement_calls(), 0); + BOOST_CHECK_EQUAL(it.advance_calls(), 2); +} Index: libs/utility/test/adv_forward_run.cpp =================================================================== --- libs/utility/test/adv_forward_run.cpp (revision 0) +++ libs/utility/test/adv_forward_run.cpp (revision 0) @@ -0,0 +1,26 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that advance() works for forward traversal iterators. +// Same implementation as for incrementable; this checks that non-exact matches +// get identified correctly. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( advance_forward ) +{ + mock_iterator<boost::forward_traversal_tag> it; + boost::advance(it, 5); + BOOST_CHECK_EQUAL(*it, 5); + BOOST_CHECK_EQUAL(it.increment_calls(), 5); + BOOST_CHECK_EQUAL(it.advance_calls(), 0); +} Index: libs/utility/test/adv_dist_hdr_compiles.cpp =================================================================== --- libs/utility/test/adv_dist_hdr_compiles.cpp (revision 0) +++ libs/utility/test/adv_dist_hdr_compiles.cpp (revision 0) @@ -0,0 +1,9 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Simple check to see if boost/utility/iterator.hpp even compiles on its own. + +#include <boost/utility/iterator.hpp> Index: libs/utility/test/adv_bidi_run.cpp =================================================================== --- libs/utility/test/adv_bidi_run.cpp (revision 0) +++ libs/utility/test/adv_bidi_run.cpp (revision 0) @@ -0,0 +1,26 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that advance() works for bidirectional traversal iterators. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( advance_bidirectional ) +{ + mock_iterator<boost::bidirectional_traversal_tag> it; + boost::advance(it, 5); + boost::advance(it, -3); + BOOST_CHECK_EQUAL(*it, 2); + BOOST_CHECK_EQUAL(it.increment_calls(), 5); + BOOST_CHECK_EQUAL(it.decrement_calls(), 3); + BOOST_CHECK_EQUAL(it.advance_calls(), 0); +} Index: libs/utility/test/dist_single_run.cpp =================================================================== --- libs/utility/test/dist_single_run.cpp (revision 0) +++ libs/utility/test/dist_single_run.cpp (revision 0) @@ -0,0 +1,23 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that distance() works for single pass traversal iterators. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( distance_single_pass ) +{ + mock_iterator<boost::single_pass_traversal_tag> it1, it2(5); + BOOST_CHECK_EQUAL(boost::distance(it1, it2), 5); + BOOST_CHECK_EQUAL(it1.increment_calls(), 5); + BOOST_CHECK_EQUAL(it1.distance_to_calls(), 0); +} Index: libs/utility/test/dist_ra_run.cpp =================================================================== --- libs/utility/test/dist_ra_run.cpp (revision 0) +++ libs/utility/test/dist_ra_run.cpp (revision 0) @@ -0,0 +1,23 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that distance() works for random access traversal iterators. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( distance_random_access ) +{ + mock_iterator<boost::random_access_traversal_tag> it1, it2(5); + BOOST_CHECK_EQUAL(boost::distance(it1, it2), 5); + BOOST_CHECK_EQUAL(it1.increment_calls(), 0); + BOOST_CHECK_EQUAL(it1.distance_to_calls(), 1); +} Index: libs/utility/test/adv_incr_run.cpp =================================================================== --- libs/utility/test/adv_incr_run.cpp (revision 0) +++ libs/utility/test/adv_incr_run.cpp (revision 0) @@ -0,0 +1,24 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that advance() works for incrementable traversal iterators. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( advance_incrementable ) +{ + mock_iterator<boost::incrementable_traversal_tag> it; + boost::advance(it, 5); + BOOST_CHECK_EQUAL(*it, 5); + BOOST_CHECK_EQUAL(it.increment_calls(), 5); + BOOST_CHECK_EQUAL(it.advance_calls(), 0); +} Index: libs/utility/test/dist_incr_fail.cpp =================================================================== --- libs/utility/test/dist_incr_fail.cpp (revision 0) +++ libs/utility/test/dist_incr_fail.cpp (revision 0) @@ -0,0 +1,17 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that distance() fails to compile for incrementable traversal iterators. + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +void distance_incrementable() +{ + mock_iterator<boost::incrementable_traversal_tag> it1, it2(5); + boost::distance(it1, it2); +} Index: libs/utility/test/mock_iterators.hpp =================================================================== --- libs/utility/test/mock_iterators.hpp (revision 0) +++ libs/utility/test/mock_iterators.hpp (revision 0) @@ -0,0 +1,72 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Implements a mock iterator template for checking iterator manipulations. + +#include <boost/iterator/iterator_facade.hpp> + +// Utility class. An iterator that globally counts calls to the core functions +// of all instances. +template <typename Traversal> +class mock_iterator + : public boost::iterator_facade< + mock_iterator<Traversal>, int, Traversal, + int, // Not a reference, to prevent merging into std:: categories. + int + > +{ +public: + mock_iterator() + : m_pos(0) + {} + mock_iterator(int pos) + : m_pos(pos) + {} + + int dereference_calls() const { return m_deref_count; } + int equal_calls() const { return m_equal_count; } + int increment_calls() const { return m_incr_count; } + int decrement_calls() const { return m_decr_count; } + int advance_calls() const { return m_advance_count; } + int distance_to_calls() const { return m_distance_count; } + +private: + friend class boost::iterator_core_access; + + int dereference() const { ++m_deref_count; return m_pos; } + bool equal(const mock_iterator &o) const { + ++m_equal_count; + return m_pos == o.m_pos; + } + void increment() { ++m_pos; ++m_incr_count; } + void decrement() { --m_pos; ++m_decr_count; } + void advance(int diff) { m_pos += diff; ++m_advance_count; } + int distance_to(const mock_iterator &o) const { + ++m_distance_count; + return o.m_pos - m_pos; + } + + int m_pos; + static int m_deref_count; + static int m_equal_count; + static int m_incr_count; + static int m_decr_count; + static int m_advance_count; + static int m_distance_count; +}; + +template <typename Traversal> +int mock_iterator<Traversal>::m_deref_count = 0; +template <typename Traversal> +int mock_iterator<Traversal>::m_equal_count = 0; +template <typename Traversal> +int mock_iterator<Traversal>::m_incr_count = 0; +template <typename Traversal> +int mock_iterator<Traversal>::m_decr_count = 0; +template <typename Traversal> +int mock_iterator<Traversal>::m_advance_count = 0; +template <typename Traversal> +int mock_iterator<Traversal>::m_distance_count = 0; Index: libs/utility/test/dist_forward_run.cpp =================================================================== --- libs/utility/test/dist_forward_run.cpp (revision 0) +++ libs/utility/test/dist_forward_run.cpp (revision 0) @@ -0,0 +1,25 @@ +// Copyright 2007 Sebastian Redl. Use, modification, and distribution are +// subject to the Boost Software License, Version 1.0. (See accompanying file +// LICENSE_1_0.txt or a copy at <http://www.boost.org/LICENSE_1_0.txt>.) + +// See <http://www.boost.org/libs/utility/> for the library's home page. + +// Check that distance() works for forward traversal iterators. +// Same implementation as for single pass; this checks that non-exact matches +// get identified correctly. + +#define BOOST_TEST_MODULE Utility_Iterator +#define BOOST_TEST_MAIN +#include <boost/test/unit_test.hpp> + +#include <boost/utility/iterator.hpp> + +#include "mock_iterators.hpp" + +BOOST_AUTO_TEST_CASE( distance_forward ) +{ + mock_iterator<boost::forward_traversal_tag> it1, it2(5); + BOOST_CHECK_EQUAL(boost::distance(it1, it2), 5); + BOOST_CHECK_EQUAL(it1.increment_calls(), 5); + BOOST_CHECK_EQUAL(it1.distance_to_calls(), 0); +} Index: libs/utility/test/Jamfile.v2 =================================================================== --- libs/utility/test/Jamfile.v2 (revision 39574) +++ libs/utility/test/Jamfile.v2 (working copy) @@ -13,6 +13,11 @@ test-suite utility : [ run ../addressof_test.cpp ] + [ compile adv_dist_hdr_compiles.cpp ] + [ run adv_bidi_run.cpp ../../test/build//boost_unit_test_framework ] + [ run adv_forward_run.cpp ../../test/build//boost_unit_test_framework ] + [ run adv_incr_run.cpp ../../test/build//boost_unit_test_framework ] + [ run adv_ra_run.cpp ../../test/build//boost_unit_test_framework ] [ run ../assert_test.cpp ] [ run ../base_from_member_test.cpp ] [ run ../binary_search_test.cpp ] @@ -20,6 +25,10 @@ [ compile-fail ../checked_delete_test.cpp ] [ run ../compressed_pair_test.cpp ../../test/build//boost_test_exec_monitor/<link>static : -u ] [ run ../current_function_test.cpp : : : <test-info>always_show_run_output ] + [ run dist_forward_run.cpp ../../test/build//boost_unit_test_framework ] + [ compile-fail dist_incr_fail.cpp ] + [ run dist_ra_run.cpp ../../test/build//boost_unit_test_framework ] + [ run dist_single_run.cpp ../../test/build//boost_unit_test_framework ] [ run ../iterators_test.cpp ../../test/build//boost_test_exec_monitor/<link>static ] [ run next_prior_test.cpp ../../test/build//boost_test_exec_monitor/<link>static ] [ compile-fail ../noncopyable_test.cpp ]

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reinterpret_cast : differents structs or classes with identical structural type
by Marco Servetto 03 Oct '07

03 Oct '07

Hello, Supposing having struct A{ int a1; double a2; int a3[3]; }; struct B{ int b1; double b2; int b3[3]; }; A and B are two structure with same strucutural type but different name, (and different name for fields...) The question is: C++ grants that A a; a.a2=8.8; assert(reinterpret_cast<B*>(&a)->b2==8.8); If the response is yes, it is even true for classes with inheritance? that is A1,B1,C1 have same struttural type of A2,B2,C2 and class A1 :public B1, class B1: public C1 and class A2 :public B2, class B2: public C2 can i safaly reinterpreter cast from A1 to A2 and acceding public fields (of A1,B1,C1) trought the field names of A2? Thanks in advance for your help.

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[review] Review of Boost.Exception
by Dean Michael Berris 03 Oct '07

03 Oct '07

Hi Everyone, Below is my review of the proposed Boost.Exception library. * What is your evaluation of the design? I personally like that the exception library is implemented in just a couple of header files, without having to drag in a lot of other libraries. It is succinctly implemented, though I have some reservations about some design decisions: get_error_info(T const &) returns a pointer instead of a const copy of the actual error_info it gets. This can be a potential headache to deal with especially in examining the error_info associated with the thrown exception. A proposed change would be to have get_error_info(T const &) return a const copy of the data, while get_error_info_ptr(T const &) would return a pointer as in the current version. Although it might also take quite some effort to remove the runtime polymorphic behavior which relies on shared_ptr<>'s and virtual tables with info_base, perhaps an expression templates-based approach to building exceptions that derive from a common base could mitigate these (theoretical) inefficiencies introduced with runtime polymorphic behavior? A linear inheritance encapsulating the different information using something like Boost.Fusion's or Boost.MPL's `fold` concept to create an exception type using expression templates might work. Then I haven't tried this myself, so it might be worth considering in the future. My concern with the use of shared_ptr<>'s is that in cases where an exception pertaining to "out of memory" conditions would arise, throwing a boost::exception and then having to allocate more memory just to encapsulate additional information would lead to undesirable termination. So keeping exception data statically allocated on the stack instead of being in the heap might be a good alternative. This is just my thinking though I don't have enough data to back this up. * What is your evaluation of the implementation? It's very cleanly implemented, and very much readable. * What is your evaluation of the documentation? The documentation is very well written although an alternative example aside from the case with file IO would be greatly appreciated. That said, the example given is sufficient enough to make a case for the utility of the library. * What is your evaluation of the potential usefulness of the library? In cases where minimal memory footprints are required, the current implementation introduces a lot of unnecessary allocations on the heap when additional information is being encapsulated into the exception. An expression templates-based approach as described above (though untested) should be able to mitigate this consequence. In all other cases where efficiency and performance are not critical, I can see this exception library to be very useful. * Did you try to use the library? With what compiler? Did you have any problems? Not yet, though I see myself using this in a project really soon. * How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? I went into the implementation details, and the conceptual design based on the source code. I did a quick read of the documentation, which didn't seem to change since the first time this library has been introduced. * Are you knowledgeable about the problem domain? I have been writing ad-hoc exception hierarchies based on std::exception for quite a while already, and I can say that this implementation of exceptions is a welcome development. * Do you think the library should be accepted as a Boost library? Be sure to say this explicitly so that your other comments don't obscure your overall opinion. I think yes, it should be accepted as a Boost library. I can see it getting a lot of improvements in terms of implementation though, but being in the Boost C++ Library will allow more people to be able to propose changes and eventually extend this library in many different ways. -- Dean Michael C. Berris Software Engineer, Friendster, Inc. [http://cplusplus-soup.blogspot.com/] [mikhailberis(a)gmail.com] [+63 928 7291459] [+1 408 4049523]

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boost::exception questions
by Tom Brinkman 03 Oct '07

03 Oct '07

1) Why cant I just throw an boost::exception object? throw boost::exception() << boost::error_info<tag_errno>(100) << boost::error_info<tag_file_name>("hello"); 2) It might be nice to support "std::cerr << e", instead of requiring the use of e.what(). std::cerr << e; 3) Support for linking multiple error tags in a single expression might be useful and help in standarizing errors throughout an application. throw boost:::exception() << boost::error_info<tag_errorno,tag_filename,tag_size,tag_width>( (1,"output.txt",100,200);

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Feedback requested: Demo build server
by Jason Sankey 02 Oct '07

02 Oct '07

Hi all, You may have noticed the discussion going on re: developer feedback systems. As part of this I have just started setting up a demo build server at: http://pulse.zutubi.com/ At this stage it is an early demonstration of the server (Pulse) building the boost trunk. There is only one machine, but for illustration purposes I am running both the master and one agent on it. This shows the ability to build on multiple agents in parallel (to test the different OS/compiler combos). In this case I am testing two different gcc versions (the easiest to setup for the demo). You will notice that the build fails, with both a bunch of errors coming out and test failures. This isn't so bad for the demo since it shows how these things are reported. In reality work would need to be done to either fix the problems or have Pulse recognise them as expected failures. You might also notice the Pulse is kicking off a build when it detects any change, and shows the change information (also linked to Trac for diff views etc). This should keep the machine busy, since a build takes over 2 hours (partly because two builds are running in parallel, but mostly just because the build takes that long). Perhaps there is a shorted build/test cycle that should be run on every change for faster feedback. On the subject of feedback, you may also want to try creating an account so you can log in. Just click the login link (top right corner) and you will see a link to sign up. It is best to choose your user name to match your Subversion user name, as then Pulse can tell which changes are yours. Once signed up you get a dashboard view along with preferences that allow you to sign up for email notifications. It would be great if people could take a look and let me know: 1) If you think this is useful and worth continuing with. 2) What important features you think are currently missing. 3) How some of the errors/failing tests can be resolved. Thanks, Jason

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Radical idea for repository structure
by David Abrahams 02 Oct '07

02 Oct '07

A few days ago I started thinking about the implications of giving each Boost library a separate subtree of the repository, and it led me to some interesting places. * Start with the assumption that each library has a boost/ directory containing its subset of the headers it currently has. So, for example, Boost.Python would have boost/ python.hpp python/ ... where "..." above is identical to the current contents of $BOOST_ROOT/boost/python/ * Our release process would merge the boost/ directories * To test a library from a source distribution, you'd need to get the boost/ directories of any libraries it depends on into the #include path. * This list of dependency libraries would be encoded in each dependent library's Jamfile. * Presto, a way to explicitly declare and track library inter-dependencies! If you fail to declare a dependency in your Jamfile, your tests won't compile. Thoughts? -- Dave Abrahams Boost Consulting http://www.boost-consulting.com The Astoria Seminar ==> http://www.astoriaseminar.com

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[Trac] Missing library/component information. (attn: library authors)
by Rene Rivera 01 Oct '07

01 Oct '07

It would be tremendously helpful to everyone if all the libraries had corresponding components and maintainers in Trac. So here's a short list of how you can help: * Read over the maintainers list in trac <http://svn.boost.org/trac/boost/report/15> * If you see a library, tool, or other component missing please respond with: the component name, the maintainer trac login name, and optionally a description of the component. * You might notice that some names are missing, even though the component has an assigned maintainer. So, also go to the list of users in Trac <http://svn.boost.org/trac/boost/report/16>. If you see the entry for yourself without a "Name" please go to the Trac settings <http://svn.boost.org/trac/boost/settings> and fill in a name. With luck, and effort, this maintainer list will be complete and we might no longer need the one in source (root/libs/maintainers.txt). -- -- Grafik - Don't Assume Anything -- Redshift Software, Inc. - http://redshift-software.com -- rrivera/acm.org - grafik/redshift-software.com -- 102708583/icq - grafikrobot/aim - grafikrobot/yahoo

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[borland] Which version of bcc32 and of Boost do you use?
by Nicola Musatti 01 Oct '07

01 Oct '07

Hallo, I'd be interested in knowing which version of Boost do people use with which version of the Borland/CodeGear compilers. The reason I'm asking relates to the state of Boost regression tests for the version currently being developed, as can be seen here: http://beta.boost.org/development/tests/trunk/developer/summary.html As you can see the situation is not very good. Moreover, while I still have to apply the latest bcbboost patches for 5.9.2, 5.6.4 and 5.8.2 should already have the same level of support they had in Boost 1.34 . Unless there's a substantial demand it looks highly likely that support for at least BCB6 will have to be dropped or, more precisely, be left to rot. Contributions are an even more effective way to avoid it :-) Cheers, Nicola -- Nicola.Musatti <at> gmail <dot> com Home: http://nicola.musatti.googlepages.com/home Blog: http://wthwdik.wordpress.com/

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[Trac] the tickets' component field lacks 'system' as a choice
by Nicola Musatti 30 Sep '07

30 Sep '07

Hallo, I tried opening a new ticket for the system library, but 'system' is not an available choice. So I had to choose 'None'. That's ticket 1293 . Cheers, Nicola -- Nicola.Musatti <at> gmail <dot> com Home: http://nicola.musatti.googlepages.com/home Blog: http://wthwdik.wordpress.com/

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