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RE: [Boost-Users] Iterator Adaptor Question
by Hickman, Greg 04 Nov '02

04 Nov '02

> -----Original Message----- > From: Mark Storer [mailto:mstorer@cardiff.com] > > You wrote up your sample so anyone could easily compile it... Thanks for noticing. :) > On > VC++ v6, I got two compiler errors: > > samplecode.cpp(58) : error C2663: 'reset' : 2 overloads have > no legal conversion for 'this' pointer > samplecode.cpp(59) : error C2678: binary '=' : no operator > defined which takes a left-hand operand of type 'const class > boost::shared_ptr<struct Shape const >' (or there is no > acceptable conversion) > > These errors are on the two lines you want to prevent. > > My first impression of the code was that it was already > illegal to perform those two actions. You shouldn't be able > to call non-const functions through a const_iterator, and > since neither reset() nor operator=() are const, no problem. > Right? I wasn't expecting the first error message, but the > second is in line with my expectations. > > I take it this code compiles for you? What tools/OS/etc are > you using? Unfortunately it does. I'm using Borland C++ Builder 5, for which I believe I have all of the available patches installed. (I'm using the IDE, but my command-line tells me I'm using Borland C++ 5.5.1. Borland gives away a set of free command-line tools that are distinct from the Builder IDE, and it may be that the compiler they give away is now more compliant than the one included in C++ Builder 5. If there is a way to point my IDE at the latest version of the free compiler, I don't know how to do it. I need to get gcc set up on my machine as a sanity check.) My first thought was that iterator_adaptor might be stripping away the const-ness from reference_type<const Const_shape_ptr>, and that the pointer type being generated was somehow pointing to a non-const Const_shape_ptr, thus allowing the indicated lines to compile. However, since you seem to get the desired results, perhaps the problem is with my compiler (or with Boost's support of it). Thanks very much for taking the time to respond. -Greg Hickman

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Property maps
by Edward Diener 04 Nov '02

04 Nov '02

The documentation for boost::property_map is awful, so would someone please explain to me what this implementation does and how it differs from std::map<> and std::multi_map<> ? I know this post sounds irascible and I am not trying to dump on Mr. Siek but really I do not understand what this idea is or why one should use it over and above what already exists in the C++ standard library. I only wish that Boost implementors would stop explaining their ideas through examples and start explaining them in logical ways in which a knowledge of the English language would suffice.

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RE: [Boost-Users] Iterator Adaptor Question
by Mark Storer 04 Nov '02

04 Nov '02

>Specifically, I'd like to prevent clients from writing the two lines >preceeding the return from main below. Can anyone help? Eh? You wrote up your sample so anyone could easily compile it... and I did. On VC++ v6, I got two compiler errors: samplecode.cpp(58) : error C2663: 'reset' : 2 overloads have no legal conversion for 'this' pointer samplecode.cpp(59) : error C2678: binary '=' : no operator defined which takes a left-hand operand of type 'const class boost::shared_ptr<struct Shape const >' (or there is no acceptable conversion) These errors are on the two lines you want to prevent. My first impression of the code was that it was already illegal to perform those two actions. You shouldn't be able to call non-const functions through a const_iterator, and since neither reset() nor operator=() are const, no problem. Right? I wasn't expecting the first error message, but the second is in line with my expectations. I take it this code compiles for you? What tools/OS/etc are you using? --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard; -----Original Message----- From: Hickman, Greg [mailto:greg.hickman@lmco.com] Sent: Friday, November 01, 2002 2:22 PM To: Boost-Users (Boost-Users(a)yahoogroups.com) Subject: [Boost-Users] Iterator Adaptor Question The following code illustrates a problem I'm having trying to use iterator_adaptor. Basically, I have a container of shared pointers to mutable, and I'd like to provide a const_iterator to clients that disallows modification of both the shared pointer as well as the pointee. Specifically, I'd like to prevent clients from writing the two lines preceeding the return from main below. Can anyone help? Thanks, Greg #include <boost/iterator_adaptors.hpp> #include <boost/shared_ptr.hpp> #include <vector> using namespace boost; using namespace std; struct Shape { virtual ~Shape() {} virtual void draw() const = 0; virtual void update() = 0; }; struct Concrete_shape : Shape { void draw() const {} void update() {} }; typedef shared_ptr<Shape> Shape_ptr; typedef shared_ptr<const Shape> Const_shape_ptr; struct Picture { typedef vector<Shape_ptr> Shapes; // Declare a const_iterator that converts // to the underlying Shape_ptr to a // Const_shape_ptr. Since the returned // Const_shape_ptr is a temporary, clients // shouldn't be allowed to modify it. typedef iterator_adaptor< Shapes::const_iterator, default_iterator_policies, value_type_is<Const_shape_ptr>, reference_is<const Const_shape_ptr>, iterator_category_is<input_iterator_tag> > const_iterator; const_iterator begin() const { return const_iterator(shapes_.begin()); } Shapes shapes_; }; int main(int argc, char* argv[]) { Picture pic; const Picture& cpic = pic; pic.shapes_.push_back(Shape_ptr(new Concrete_shape)); Picture::const_iterator i = cpic.begin(); // I'd like to prevent clients from writing... i->reset(new Concrete_shape); *i = Const_shape_ptr(new Concrete_shape); return 0; } Info: <http://www.boost.org> Wiki: <http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl> Unsubscribe: <mailto:boost-users-unsubscribe@yahoogroups.com> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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Bug fix for format library
by Fred Jackson 04 Nov '02

04 Nov '02

I found a bug in the format library and fixed it. strm << boost::format("%64.64s") % "hello"; gave an access violation. It was caused by passing an argument greater than the string length to std::string::erase. I added a check so as not to try to erase text that is not there. Here is a diff of my small fix. < is feed_args.hpp from the boost_1_29_0 distribution. > is my fixed file. 158c158,162 < if (specs.truncate_ >= 0) --- > // @@@@@ fjackson 20021022 Added test to make sure we don't call > // std::string::erase with an arg greater than the length - this > // caused an access violation, noted on outputting a short string > // with a %64.64 format specifier. > if (specs.truncate_ >= 0 && specs.truncate_ < res.length())

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Wrapping a std::list with boost.python
by jefflholle 03 Nov '02

03 Nov '02

I've just started experimenting with version 2 of boost.python. In iterator.cpp, a std::list is wrapped using following code: typedef std::list<int> list_int; void push_back(list_int& x, int y) { x.push_back(y); } int back(list_int& x) { return x.back(); } . . . class_<list_int>("list_int") .def("push_back", push_back) .def("back", back) .def("__iter__", iterator<list_int>()) ; Is it possible to use the container methods instead of user defined functions? I've tried the code: class_<list_int>("list_int") .def("push_back", &list_int::push_back) .def("back", &list_int::back) .def("__iter__", iterator<list_int>()) ; This doesn't work. Am what I'm tried to do possible? If so, how?

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Re: linker problem with boost::thread
by Eske Christiansen 03 Nov '02

03 Nov '02

sorry, have fixed the problem. the correct way of linking with boost::thread is: g++ foo.cpp -lboost_thread -lpthread yours eske

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Making boost/test pause so the console can be read when running the tester from an IDE.
by Sean Shubin 03 Nov '02

03 Nov '02

My version of C++ builder does not pause to let me see console output. This makes it difficult to use boost/test while I am running the program from the IDE. The solution I found most useful, is to make the last test wait for the user to press enter. If anyone has solved this a different way, I would like to hear about it. #include <boost/test/unit_test.hpp> using boost::unit_test_framework::test_suite; using std::cout; using std::cin; using std::endl; void waitForUserToPressEnter() { cout << "Press <ENTER> to continue..." << endl; cin.get(); } test_suite* init_unit_test_suite(int argc, char* argv[]) { test_suite* test = BOOST_TEST_SUITE("Master test suite"); //add other tests here test->add(BOOST_TEST_CASE(&waitForUserToPressEnter)); return test; }

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linker problem with boost::thread
by Eske Christiansen 02 Nov '02

02 Nov '02

Hi all I'm new to this list and I have a question. I want to use the thread lib in g++ 2.96.110 under redhat 7.3 I have the test e.x. #include <boost/thread/thread.hpp> #include <iostream> void hello() { std::cout << "Hello world, I'm a thread!" << std::endl; } int main(int argc, char* argv[]) { boost::thread thrd(&hello); thrd.join(); return 0; } (from cuj.com) I try to compile with g++ -lboost_thread foo.cpp I get the the error(s): /tmp/ccdoKT37.o: In function `main': /tmp/ccdoKT37.o(.text+0x53): undefined reference to `boost::thread::thread(boost::function0<void, boost::empty_function_policy, boost::empty_function_mixin, allocator<boost::function_base> > const &)' /tmp/ccdoKT37.o(.text+0x75): undefined reference to `boost::thread::join(void)' /tmp/ccdoKT37.o(.text+0x86): undefined reference to `boost::thread::~thread(void)' /tmp/ccdoKT37.o(.text+0xbe): undefined reference to `boost::thread::~thread(void)' collect2: ld returned 1 exit status What do I do wrong. I don't want to use jam og bjam files because all my works i build by using automake. yours eske

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Basic Overviews Needed
by Sam Gentile 02 Nov '02

02 Nov '02

Hi Folks, I am new to Boost. I have looked at the Boost Documentation on the web (http://www.boost.org/libs/libraries.htm) and although it does a very excellent job of listing all the libraries, it doesn't really have any overview documents or tutorials as such. What I would like is some documents that tell me the power of Boost, what its useful for, etc. Any help would be greatly appreciated. Sam Gentile .NET Consultant ManagedCode(a)attbi.com http://www.samgentile.com http://radio.weblogs.com/0105852/ [Non-text portions of this message have been removed]

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compiler warning
by Matthew Galati 01 Nov '02

01 Nov '02

hi, using gcc version 2.96 20000731 (Red Hat Linux 7.3 2.96-110) does anyone know the pragma for turning this compiler warning off? or is this warning telling me something - do i need to configure my compiler differently? /home/mgalati/source/boost_1_29_0/boost/integer_traits.hpp:186: warning: ISO C++ does not support `long long' thanks, matt

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