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mpl error message on icc
by Stefan Strasser 05 Apr '05

05 Apr '05

this code has always been working on gcc but doesn't on icc, can anyone tell me what's wrong here: typedef mpl::copy<AMplVector,mpl::back_inserter<mpl::vector<AnotherMplVector> > >::type Type; I removed namespace qualifiers and so on from the error message but it's still not very readable: detected during: instantiation of class "mpl::aux::fold_impl<4, First, Last, State, ForwardOp> [with ... /usr/include/boost/mpl/aux_/preprocessed/plain/fold_impl.hpp(115): error: class "mpl::apply2<mpl::inserter<mpl::vector<Element, Declaration, NameDeclaration, Member, MemberClassifier, TemplateDeclaration, TemplateClassifier, MemberTemplateClassifier , Type, Classifier, Class, MemberClass, TemplateClass, MemberClassifierDefinition, ClassifierDefinition, TemplateClassifierDefinition, ClassDefinition, mpl::na, mpl::na, mpl::na>, mpl::push _back<mpl::na, mpl::na>>::operation, mpl::aux::fold_impl<4, mpl::begin<MemberTemplateClassDefinitionImpl::Bases>::type, mpl::en d<MemberTemplateClassDefinitionImpl::Bases>::type, mpl::inserter<mpl::vector<Element, Declaration, NameDeclaration, Member, MemberClassifier, TemplateDeclaration, TemplateClassifier, MemberTemplateClassifie r, Type, Classifier, Class, MemberClass, TemplateClass, MemberClassifierDefinition, ClassifierDefinition, TemplateClassifierDefinition, ClassDefinition, mpl::na, mpl::na, mpl::na>, mpl::push_back<mpl::na, mpl::na>>::state, mpl::inserter<mpl::vector<Element, Declaration, NameDeclaration, Member, Memb erClassifier, TemplateDeclaration, TemplateClassifier, MemberTemplateClassifier, Type, Classifier, Class, Me mberClass, TemplateClass, MemberClassifierDefinition, ClassifierDefinition, TemplateClassifierDefinition, ClassDefinition, mpl::na, mpl::na, mpl::na>, mpl::push_back<mpl::na, mpl::na>>::operation>::state3, mpl ::deref<mpl::aux::fold_impl<4, mpl::begin<MemberTemplateClassDefinitionImpl::Bases>::type, mpl::end<MemberTemplateClassDefinitionImp l::Bases>::type, mpl::inserter<mpl::vector<Element, Declaration, NameDeclaration, Member, MemberClassifier, TemplateDeclaration, TemplateClassifier, MemberTemplateClassifier, Type, Classifier, Class, MemberClass, TemplateClass, MemberClassifierDefinition, ClassifierDefinition, TemplateClassifierDefinition, ClassDefinition, mpl::na, mpl::na, mpl::na>, mpl::push_back<mpl::na, mpl::na>>::state, mpl::inserter<mpl::vector<Element, Declaration, NameDeclaration, Member, MemberClassifier, Te mplateDeclaration, TemplateClassifier, MemberTemplateClassifier, Type, Classifier, Class, MemberClass, Templ ateClass, MemberClassifierDefinition, ClassifierDefinition, TemplateClassifierDefinition, ClassDefinition, mpl::na, mpl::na, mpl::na>, mpl::push_back<mpl::na, mpl::na>>::operation>::iter3>::type>" has no member "type" typedef typename apply2< ForwardOp, state3, typename deref<iter3>::type >::type state4; regards, -- Stefan Strasser

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about enable_if for member functions
by Yutaka Leon Suematsu 04 Apr '05

04 Apr '05

Dear booster, I have a question related to enable_if. I would like to enable or disable some member functions from a template class, but enable_if is -not enable- to do it :-) Here is the code. template <class T> class A { ... enable_if< boost::is_arithmetic<T>, void > :: type f1() { ... } }; In class A, I want to define function f1 only if the template parameter is arithmetic. It works fine except when the parameter is not arithmetic. I have a compile error "error C2039: 'type' : is not a member of 'boost::enable_if<Cond,T>'" (Working with VC7.1, and boost 3.12) Thank you in advance for any suggestions and help. Sincerely yours, Yutaka Leon Suematsu

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Re: Re: STL algorithms & references (David Abrahams)
by Sean DeNigris 04 Apr '05

04 Apr '05

To anyone interested, I ended up writing for_each<cIterType&>(.) and the algorithm passed the iterators by reference. - Sean >typedef set<int>::const_iterator cIterType; >cIterType bit = mySet.begin(); cIterType eit = >mySet.end(); > >for_each(ref(bit), ref(eit), > if_(bind(boost::next<cIterType>, boost::ref(bit)) != mySet.end()) > [...]

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Re: unordered_map has no lower_bound?
by Gottlob Frege 04 Apr '05

04 Apr '05

> Date: Mon, 04 Apr 2005 16:39:34 +0100 > From: Ben Hutchings <ben.hutchings(a)businesswebsoftware.com> > Subject: Re: [Boost-users] Re: unordered_map has no lower_bound? > To: boost-users(a)lists.boost.org > Message-ID: <42515FB6.9040803(a)businesswebsoftware.com> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Daniel James wrote: > >> Martin Wartens wrote: > >> > >>> PS: there is a small problem in hash_table.hpp causing a warning in > >>> VC7.1 > >>> line 278 should be: > >>> return (*prev_ptr)!=0; > >>> instead of > >>> return *prev_ptr; > > > > > > Ah, I just found out why I didn't do this before - prev_ptr might be a > > pointer object (depending on the allocator), so the correct line is: > > > > return (*prev_ptr) != link_ptr(); > > > > Which can potentially be inefficient. I think the best thing to do is to > > use a pragma to disable the warning, > > If it's the warning I'm thinking of (C4800: "forcing value to bool > 'true' or 'false'" - well, *duh*) then this is the right approach. > > > or maybe: > > > > return static_cast<bool>(*prev_ptr); > > > > or: > > > > return boost::implicit_cast<bool>(*prev_ptr); > > > > would work. > > Neither of those prevents the warning. > > Ben. > I always use !! to prevent that warning. like return !!*prev_ptr; YMMV.

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C++ Template Metaprogramming -- EX 2.1
by Kelly Burkhart 04 Apr '05

04 Apr '05

I'm going through the excercises in this book and am stumped on the second one I tried. Does anyone have a hint on how to approach this problem? TIA, -K

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Problems on list cover page
by David Abrahams 04 Apr '05

04 Apr '05

HTML tags seem to be showing up as text in the resulting web page: http://lists.boost.org/mailman/listinfo.cgi/boost-users -- Dave Abrahams Boost Consulting www.boost-consulting.com

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serialization
by Damien * 04 Apr '05

04 Apr '05

has anyone seen this compile error before, and know how to fix it? /usr/local/include/boost-1_32/boost/archive/detail/iserializer.hpp:428: no type named `type' in `struct boost::mpl::eval_if<boost::is_abstract<MyClass>, boost::mpl::identity<boost::archive::detail::load_pointer_type<boost::archive::text_iarchive, MyClass*>::abstract<MyClass> >, boost::mpl::identity<boost::archive::detail::load_pointer_type<boost::archive::text_iarchive, MyClass*>::non_abstract<MyClass> > >' im trying to serialize a polymorphic class that has a pointer to another class of the same type in it. if i comment out that line in the serialization function, the error goes away.

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Re: STL algorithms & references
by David Abrahams 04 Apr '05

04 Apr '05

The following message is a courtesy copy of an article that has been posted to comp.lang.c++.moderated as well. lotusny78(a)yahoo.com writes: > Is there an "easy" way to pass iterators by reference to STL > Algorithms? By easy, I mean not more complicated than using a for > loop. > > e.g. > typedef set<int>::const_iterator cIterType; > cIterType bit = mySet.begin(); > cIterType eit = mySet.end(); > > for_each(ref(bit), ref(eit), > if_(bind(boost::next<cIterType>, boost::ref(bit)) != mySet.end()) > [...] > ); > > The code above, using boost::ref does not compile, at least in part > because boost::reference_wrapper does not contain some STL typedefs. > > If anyone has any ideas, I'd appreciate them. Thanks. This is clearly (to me, but probably not to most other readers of this NG) a Boost.Lambda - related question. If you post it to an appropriate mailing list (see http://www.boost.org/more/mailing_lists.htm) you'll probably get more useful answers. HTH, -- Dave Abrahams Boost Consulting www.boost-consulting.com

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GNU GPL
by Uzytkownik 04 Apr '05

04 Apr '05

-----BEGIN PGP SIGNED MESSAGE----- Hash: RIPEMD160 Could I use Boost in program under GPL? Regards. - -- Linux user: #376500 (patrz http://counter.li.org/) -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQFCTuvOTCh1hBPsbHURA3shAJ4hncUNBBtoM/V0w8501V3IQE51EwCfUjzJ lxP2qbr+XskDCWmhussuxSU= =uJJp -----END PGP SIGNATURE-----

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[string_algo] new flavour of xxx_copy algorithms
by Yuval Ronen 03 Apr '05

03 Apr '05

Hi. Many algorithms in the string-algo library have 3 versions (I'll take to_upper as an example): 1. In-place modification which takes a SequenceT by ref: template<typename MutableCollectionT> void to_upper(MutableCollectionT &); 2. Copy version which takes a SequenceT by const ref, and returns SequenceT: template<typename SequenceT> SequenceT to_upper_copy(const SequenceT &); 3. Copy version which takes a const ref CollectionT and an OutputIteratorT and the OutputIteratorT after using it: template<typename OutputIteratorT, typename CollectionT> OutputIteratorT to_upper_copy(OutputIteratorT, const CollectionT &) I believe there's room for another version - something that takes a const ref CollectionT, and returns a copy in a SequenceT: template<typename SequenceT, typename CollectionT> SequenceT to_upper_copy(const CollectionT &); The benefits are ease of use combined with performance. IMO, a common scenario is to perform a copy algorithm on a char* string, and returning it as a std::string. Such a thing would be easily done with the proposed extension as: std::string str = to_upper_copy<std::string>("something"); As it is now, I either have to make additional copy (if I use the in-place modification version or the SequenceT copy version), or handle the std::string size my self (if I use the OutputIteratorT version). The new version will allow me to do it elegantly and efficiently. The problem is that it probably can't be an overload of to_upper_copy because it has the same number of arguments as one of the existing overloads, so it will have to have a different name :-( Thanks, Yuval

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