September 2003 - Boost-users - lists.preview.boost.org

ostream_iterator and std::copy - better solutions?
by Jeff Flinn 03 Sep '03

03 Sep '03

Before rolling my own, does boost have a facility to stream out an iterator range without the dangling delimiter at the end? For example std::ostream& operator<<( std::ostream& s, const MyClass& aC ) { const std::string lDelim( "," ); std::vector<int> lInts; lInts.push_back(1); lInts.push_back(2); lInts.push_back(3); std::ostream_iterator<int> lItr( s, lDelim.c_str() ); std::copy( lInts.begin(), lInts.end(), lItr ); } yields: 1,2,3, I'm … [View More]

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RE: [Boost-Users] boost lambda examples
by Paul Grenyer 03 Sep '03

03 Sep '03

Hi Matt > > >for_each( v.begin(), v.end(), cout << *_1 << '\n' ); > > >I get the following errors: > That only makes sense with vector<int*>... as per the example, from > memory... > I think you meant vp.begin() etc. Yes, that's it! So what I actually wanted was: for_each( v.begin(), v.end(), cout << _1 << '\n' ); That'll teach me copy code from two different examples without applying my brain to it. Thanks, Matt! Regards … [View More]

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boost lambda examples
by paulgrenyer 03 Sep '03

03 Sep '03

Hi MSVC 7.1, Windows 2000 I'm trying to get to grips with the boost lambda library. I've managed to get the first example to work: #include <boost/lambda/lambda.hpp> #include <iostream> #include <cstdlib> #include <list> #include <algorithm> int main() { using namespace std; using namespace boost::lambda; list<int> v(10); for_each(v.begin(), v.end(), _1 = 12 ); return EXIT_SUCCESS; } but when I add the following line (also from the docs): … [View More]

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RE: [Boost-Users] boost lambda examples
by Hurd, Matthew 03 Sep '03

03 Sep '03

>From: paulgrenyer [mailto:pjgrenyer@iee.org] >Subject: [Boost-Users] boost lambda examples >for_each( v.begin(), v.end(), cout << *_1 << '\n' ); >I get the following errors: That only makes sense with vector<int*>... as per the example, from memory... I think you meant vp.begin() etc. Cheers, Matt.

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"invalid token pasting" macro bug
by James W. Walker 03 Sep '03

03 Sep '03

When I use Spirit with CodeWarrior 9 (just released), I get a bunch of warnings as shown below. The CodeWarrior release notes explain that "According to the language standard, the '##' token pasting operator can only generate other tokens. This warning indicates when a paste was found that did not result in a token. The code will still compile as it did previously, but it may be a useful hint if the compiler emits an error later on." Warning : invalid token pasting of '… [View More]

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how to create fixtures in unit test framework
by Anders Moe 03 Sep '03

03 Sep '03

Hi all. The boost unit test framework seems to lack the xUnit buildUp/tearDown (whatever) methods meant to faciliate the creation of fixtures. Does that mean there is an alternative idiom to achieve the same effect ? Constructing new class-test-cases for each test seems a bit overkill. Regards, Anders.

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Lambda operator= question
by Rodolfo Lima 02 Sep '03

02 Sep '03

Hi people, That's the first time I'm using lambda and I'm stuck with something that can be resumed to: struct A { int Test() { return 0; } }; int x; A a; (var(x)=bind(&A::Test,_1))(a); In other words, I want to make a functor that calls a member function and stores its return value in some variable. I'm compiling with VC7.1 and it returns error C2440: '=' : cannot convert from 'const boost::tuples::cons<HT,TT>::stored_head_type' to 'int' Is there something I can do to get rid … [View More]

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CodeWarrior PS2, Boost, & STL
by Yohann DOS SANTOS 02 Sep '03

02 Sep '03

Hello Boost Users, When i try to compile a class that use a vector with CodeWarrior for PS2 R3.03, i have this error message : Error : illegal use of incomplete struc/union/class 'Metrowerks::compile_assert<0>' (instantiating: 'std::vector<int, std::allocator<int>>') (instantiating: 'std::__vector_imp<int, std::allocator<int>, l>') vector line 729 ompile assert<bool(sizeof(T) == sizeof(typename Metrowerks::strore_as<T>;;type))> And just above the … [View More]

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[BGL] Adding one graph to another
by Tarjei Knapstad 02 Sep '03

02 Sep '03

I need to add/copy one graph into another, both completely connected, and then create an edge between one vertex in the original graph and a vertex in the one copied into it. The edge/vertex properties needs to be copied as well, and this needs to be fairly efficient. The new edge is straightforward, but is there any functionality for the copy/add operation? (Something like an "add_component" algorithm I guess...) To my understanding both the copy_graph and copy_component algorithms both … [View More]

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spirit list_p example
by Larry 02 Sep '03

02 Sep '03

From boost-1.30.2 I built the list_parser.cpp example using MSVC++7.1. In the CSV list I added ",,2" to the end of the line to be parsed. The program ran but the neither of the added elements were included in the output vector. Having used the tokenizer before I know it will generally gobble up adjacent delimiters without any output. You can get the empty token if you ask for the delimiters as well and then just discard the delimiters (sort of). But I was surprised that the 2 didn't make … [View More]

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adjancency propoerty iterator
by sashan 02 Sep '03

02 Sep '03

Hi Is there an adjancency iterator for property types. You can get an iterator for property types like this: typedef graph_property_iter_range<GraphType, vertex_name_t>::iterator VNameIterator; .... tie(It, ItEnd) = get_property_iter_range(m_Graph, vertex_name); I'd like to know if there is something similar for adjacency iterators. Thanks [Non-text portions of this message have been removed]

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RE: [Boost-Users] Given std::map<ID,struct>, efficient way to access std::vector<struct.member>?
by Sam Partington 01 Sep '03

01 Sep '03

Well, I've trimmed you're example down some more, as to me it didn't seem to be important that the struct was a member of CFilter. So I think your question boils down to : struct A { int a; }; typedef std::map<int, A> my_map; void do_something_on_a_slice(int a) { // whatever } void f(const my_map& map_) { std::for_each(map_.begin(), map_.end(), /*what goes here*/); } You could use iterator_adaptors for this, but I think that is complicating things unnecessarily, something like … [View More]this would work (untested) : struct select_a : std::unary_function<my_map::value_type, int> { const result_type& operator()(const argument_type& arg) const { return arg.second.a; } // similar non const operator here }; void f(const std::map<int, A>& map_) { boost::projection_iterator_generator<select_a, my_map::const_iterator>::type first(map_.begin()), last(map_.end()); std::for_each(first, last, do_something_on_a_slice); } See http://www.boost.org/libs/utility/projection_iterator.htm But I think bind in this situation is a better solution. (Partly because the interface to iterator_adaptors will be changing in the next release, possibly to the point of breaking the above code - Jeremy?) void f(const my_map& map_) { using boost::bind; std::for_each(map_.begin(), map_.end(), bind(do_something_on_a_slice, bind(&A::a, bind(&my_map::value_type::second, _1) ) ) ); } Though at this point I would consider writing a function object, any expression involving three bind's is getting close to (or some might say past) write-only code. As to efficiency, if this is a bottleneck it is mostly likely the iteration over the map that is causing the problem, or the actual 'doing' code. Most of the binding code should be optimised away by the compiler to a bare mimimum. It may be that you are better changing container, a sorted vector perhaps. HTH Sam (PS Apologies if I did miss a point somewhere and oversimplify your code) Chris Russell <> wrote: > Hello folks, I've got an interesting little design problem > and I'm looking > for some advice on how best to implement an efficient solution. (snip) > Here's a simplified statement of the problem that I believe > outlines the > relevant details: > > I've got a class declared as follows: > > --- begin example class ---- > In English: CFilter declares some structure with some number > of data members > of arbitrary types. Internally CFilter allocates a std::map of these > structures using some key_t. Effectively this defines a table > of data whose > rows are of type sRow_t, and whose columns can be conceptualized as > std::vector<A_t>, std::vector<B_t> where > std::vector<sRow_t.some_member>.size() == mapData<key_t, > sDataRow_t>.size(). > > At runtime, CFilter.ProcessRow is called std::map<key_t, > sRow_t>.size() times followed by a single call to CFilter.ProcessData. > > I'm trying to figure out how to _efficiently_ access the > column vectors in > the implementation of CFilter.ProcessData. [View Less]

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