- Boost-users - lists.boost.org

boost::bind and member functions
by David Morrison 23 Mar '05

23 Mar '05

Hi, I'm interested in using boost::bind and std::transform to iterate through a container of member functions and initialize another container with the results. I've read through the documentation pretty carefully - in particular this bit from the bind documentation: typedef void (*pf)(int); std::vector<pf> v; std::for_each(v.begin(), v.end(), bind(apply<void>(), _1, 5)); So I've been able to iterator through a set of *non* member functions and intialize another container with the results. When I try the code below, I get the following error message: boost/bind/apply.hpp:39: must use .* or ->* to call pointer-to-member function in `f (...)' I have tried several variations involving mem_fn to try and create the appropriate functors, but so far, no joy. Is there a known solution to accomplish what I want to do? Dave #include <vector> #include <iostream> #include <iterator> #include "boost/bind.hpp" #include "boost/bind/apply.hpp" using namespace std; using namespace boost; struct A { float a(int m, float x) { return m * x;} float b(int m, float x) { return m + x;} float c(int m, float x) { return m - x;} float d(int m, float x) { return m / x;} }; typedef float (A::*pfn)(int, float); int main() { A a; int m = 2; float x = 3.0; vector<pfn> v; vector<float> f; v.push_back(&A::a); v.push_back(&A::b); v.push_back(&A::c); v.push_back(&A::d); transform(v.begin(), v.end(), back_inserter(f), bind(apply<float>(), _1, a, m, x)); copy(f.begin(), f.end(), ostream_iterator<float>(cout, "\n")); }

3 7

filter_iterator question
by steve ahlgren 22 Mar '05

22 Mar '05

Hello all : I have a filter_iterator question. I'm wondering if, conceptualy, I can construct an FI doing something like the following : typedef boost::filter_iterator< boost::bind( boost::mem_fn( &MyObject::HasQuality ), boost::ref( quality ) ), MyIterator > FilteredIterator; Instead of defining an explicit functor like this : struct MyFunctor { bool operator()( const MyObject& obj ) const { etc } }; and the FI like this : typedef boost::filter_iterator< MyFunctor, MyIterator > FilteredIterator; Gosh! Writing functors is flipping waste of time! Has anyone used the former construct instead? Thanks in advance! SGA

2 1

BGL: Undirected graphs and max flow
by Cyrille Damez 22 Mar '05

22 Mar '05

Hi all, I realize this might sound a little dumb, but I can't find in the documentation how to use (if it is possible at all) the push_relabel_max_flow function with undirected graphs. The problem is that push_relabel_max_flow requires an edge property that maps each edge to a reverse edge, which seems redundant when the graph type is undirected. Thanks,

3 2

RE: [Boost-users] Re: map with minimal memory footprint
by Jim.Hyslop 22 Mar '05

22 Mar '05

Gottlob Frege wrote: > I believe you, but can you explain what you mean by "iterator > invalidation properties". I wrote a vector_map once, and it was as > "map-ish" as needed at the time, so I suspect it was just a "useful > associative container", but I'm just curious as to what I was > missing... When you insert or erase elements in a container, The Standard imposes requirements on what happens to iterators and references you have to elements in a container. All map iterators and references must remain valid after inserts. After erasing, only iterators and references to the erased element are allowed to be invalidated. Inserts into vectors (including via 'resize' or 'reserve') can invalidate all references and iterators, if the vector has to reallocate; otherwise, only references and iterators to elements prior to the one being inserted remain valid. Erasing invalidates iterators and references to elements after the one being erased. If you have a copy of the Standard, search for "invalidate" in section 23 for full details. -- Jim Hyslop Senior Software Designer Leitch Technology International Inc. ( http://www.leitch.com ) Columnist, C/C++ Users Journal ( http://www.cuj.com/experts )

1 0

Serialization library
by Przemyslaw Sliwa 22 Mar '05

22 Mar '05

All, I would like to ask you a question if someone of you has ever used the boost serialization library. I managed to compile with VC++ 7.1 the sample code from the example website http://www.boost.org/libs/serialization/example/demo.cpp. It went well, but it is giving some strange run time errors. I managed to compile just in the debug mode and it does not work with the Release one. I am getting some strange link errors. There are several libraries in the serialization module and basically there is nothing about it which one should be used. Can you help me with it? The examples use just the text archive. The serialization module is huge and I know there are several other modes, e.g. XML, etc. The problem is lack of any kind of documentation. Does anyone of you use other archive types than the text ones? Thanks for help in advance -- This e-mail may contain confidential and/or privileged information. If you are not the intended recipient (or have received this e-mail in error) please notify the sender immediately and destroy this e-mail. Any unauthorized copying, disclosure or distribution of the material in this e-mail is strictly forbidden.

2 1

Re: map with minimal memory footprint
by Gottlob Frege 22 Mar '05

22 Mar '05

> 6. Re: map with minimal memory footprint (David Abrahams) > Date: Wed, 16 Mar 2005 09:45:34 -0500 > From: David Abrahams <dave(a)boost-consulting.com> > Subject: [Boost-users] Re: map with minimal memory footprint > To: boost-users(a)lists.boost.org > Message-ID: <uoedjd4z5.fsf(a)boost-consulting.com> > Content-Type: text/plain; charset=us-ascii > > Toon Knapen <toon.knapen(a)fft.be> writes: > > > Hi all, > > > > I'm using a rather big std::map which gives good performance but the > > memory footprint is a bit too big. So I figured to implement an std::map > > as an std::vector<std::pair<T1,T2>> but thus with the interface of an > > std::map on top of it. > > Can't be done. It has the wrong iterator invalidation properties. > You may be able to implement a useful associative container, but it > will never be std::map. > > -- > Dave Abrahams > Boost Consulting > www.boost-consulting.com > I believe you, but can you explain what you mean by "iterator invalidation properties". I wrote a vector_map once, and it was as "map-ish" as needed at the time, so I suspect it was just a "useful associative container", but I'm just curious as to what I was missing...

1 0

Re: [shared_ptr] get_deleter is for what?
by Mark Holloway 22 Mar '05

22 Mar '05

Ben Hutchings Wrote: >> I realise my requirements may be rather specific, but it seems >> shared_ptr has picked up some typeid baggage, which I can't afford. > Whyever not? Sorry - I wasn't playing the image size limitation game - it's just I'd rather class names were not revealed to the average image browser. Peter Dimov Wrote: >This problem should be fixed in the latest CVS version of boost::shared_ptr. >If you can try it and report back, it would be much appreciated. Will do. Thanks for the info Peter. Mark

1 0

[shared_ptr] get_deleter is for what?
by Mark Holloway 22 Mar '05

22 Mar '05

I realise my requirements may be rather specific, but it seems shared_ptr has picked up some typeid baggage, which I can't afford. I'm compiling using MSVC7.1 and for each object for which I use a shared_ptr, I gain an entry in my binary. For example, class Monty generates the following string in my exe: ?AU?$checked_deleter@VMonty@@@boost@@ This seems to be sucked in by this function in class sp_counted_base_impl: virtual void * get_deleter(std::type_info const & ti) { return ti == typeid(D)? &del: 0; } It isn't being used, and I can't actually see anything in boost using this, so maybe the compiler isn't doing a great job at stripping unused stuff? Anyone shed some light on this for me? Thanks Mark

3 2

boost parallel build, will it get better?
by Daniel Goller 22 Mar '05

22 Mar '05

Hi, i was wondering if there is a possibility boost (bjam?) will be supporting parallel builds better in the future, i was testing building with -j5 (-j5 is about the sweet spot at which distcc creates enough load on the helping XP3200 for this mac mini i work on) and boost was no longer able to successfully build, something it did before readding support for the user selected number of jobs. Basically im wondering what to tell users who start to notice we do not support their -jN settings ("bear with us it'll work in future" vs "we do not know if it will ever work") after having received notice that supporting make options might not be taken well by bjam (and being able to confirm this with distcc), while at the same time wishing i could take advantage of distcc myself. Is this something of concern to boost, or will it most likely remain at the state as it is in the 1.32.0 release? Thanks in advance for any information you can provide. Daniel

5 5

runtime polymorphism & passing and returning elements
by Kosta 22 Mar '05

22 Mar '05

The problem is not boost specific, but probably there is a boost specific solution to it... The usual way of passing and returning elements to/from a function/method is to use a templated function/method, e.g.: template< typename ITER_IN, typename ITER_OUT > void doSomething( ITER_IN inBegin, ITER_IN inEnd, ITER_OUT outIter, int param1, int param2, ... ) { while(inBegin != inEnd) { ... *outIter++ = ...; } } But what to do in case of (pure) virtual methods which can't be templated? One (neither pretty nor efficient) solution would be something like this: struct A { template<typename ITER_IN, typename ITER_OUT> void doSomething( ITER_IN inBegin, ITER_IN inEnd, ITER_OUT outIter, int param1, int param2, ... ) { const std::vector<int> out( doSomething_impl( std::vector<int>(inBegin, inEnd), param1, param2 ) ); std::copy(out.begin(), out.end(), outIter); } virtual std::vector<int> doSomething_impl( std::vector<int>& const in, int param1, int param2, ... ) = 0; }; // struct A Is there a better (boost-ish) solution?

1 0