March 2009 - Boost-users - lists.preview.boost.org

Returning a shared_ptr or raw pointer from a template function
by Ryan McConnehey 31 Mar '09

31 Mar '09

I want to allow the user to specify if a function returns a raw pointer or a shared_ptr from a creation type function. The code I've started with is as follows: class Track{}; class Tm{}; template <class R, class T> R create(void) { R temp(new T()); return temp; } This allows to the user to call the function like: Tm* tm3 = create<Tm*, Tm>(); boost::shared_ptr<Tm> tm4 = create<boost::shared_ptr<Tm>, Tm>(); I would like to have a class that has this create function and upon creation of the class specify if the create function returns a raw pointer or shared_ptr. template <class U> //The U specifies is the create function returns a raw or shared pointer class Rdi { template <class S> U create(void) { U temp(new S()); return temp; } }; How would I modify this class to allow the user to make the following calls? Rdi<boost::shared_ptr> fun1; Tm* tm3 = fun1.create<Tm>(); Rdi<raw Pointer???> fun2; boost::shared_ptr<Tm> tm4 = fun2.create<Tm>(); Any help would be appreciated. Ryan

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[wave]include not found
by Ein Held 31 Mar '09

31 Mar '09

Hello According to the wave documentation, the include folder functions of the context object work "are modelled after the command line behaviour implemented by the popular gcc compiler." Unfortunately this is wrong. By default gcc 4.x -Is' folders (when not used with -I-) are searched for "...." and <...> include files. Wave does not do so. Anyway, I am searching for a solution for this problem: Lets say I got a file named dub.cpp that I am parsing with wave and that looks like that: #include <foo/bar.hpp> int main{} bar.hpp looks like this: #include "test.hpp" extern int a; test.hpp is just an empty file in the same folder as bar.hpp I added the parent folder of foo to the wave context object via add_sysinclude_path . Unfortunately wave does not find the file test.hpp (exception - "error - could not find include file"). I tried nearly all possible combinations of add_include_path, add_sysinclude_path, set_sysinclude_delimiter - but I have not succeeded. This simple sample is still failing.. gcc -c -I"/foo/parent/folder" dub.cpp works fine though. Whats wrong?

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Completely Perplexed Noob to BGL: Reachability Question
by Roshan Rammohan 31 Mar '09

31 Mar '09

Hi all, Although I was attracted to BGL since I have to use a lot of graph algorithms for my work, and I have managed to read through as much online documentation as possible, generic programming is still very mysterious to me. All I need to do is compute reachability from vertex B to vertex A before I add the edge A->B to a graph (directed and acyclic) so that I can maintain its acyclic property. I do not want to add the edge, discover a cycle and then remove it. I saw a very closely related example here. (thanks to Steven Watanabe) http://lists.boost.org/boost-users/2009/03/46396.php That was helpful, but I'm still not able to adapt this to my need mainly because I find the syntax and concepts of generic programming extremely confusing. I am not sure how I can pass an extra parameter into a BFSVisitor which the member function discover_vertex can use. Does discover_vertex have to have only a vertex_descriptor and a Graph? I want to pass another constant vertex to it so I can return on equality. I need to initiate a BFS from vertex B, (and not continue with new trees once the tree with B as root is finished) . On discovering vertex A in this search I need to return true, false for all other cases. Pretty simple, and I am hoping someone would write a code snippet for me that will solve the problem and also provide me with the baby step I need to wrap my head around this Visitor concept. Thanks in advance. - Roshan Rammohan PhD Candidate, A.I. lab, Dept of C.S., Univ. of New Mexico, USA

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[statechart] state behaviour
by liquid 30 Mar '09

30 Mar '09

Hi, two questions about states in statechart: 1. How (if possible) to implement this: a state upon an event generates an event and transits to another state? 2. Can a state have private nondestroyable memory? Regards liquid

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Re: [Boost-users] regex iterator question
by Mike Marchywka 30 Mar '09

30 Mar '09

---------------------------------------- > To: boost-users(a)lists.boost.org > Date: Mon, 30 Mar 2009 12:48:48 -0400 > From: dfs(a)savarese.org > Subject: Re: [Boost-users] regex iterator question > > > In message , "Robert Ramey" writes: >>Thinking about it, this problem must come very often. How is it usually >>addressed? There must be a simple bridge across this. In a pinch, I'll >>just have to load the whole file into some sort collection, but I prefer the >>ultimate unlimited file size solution. > I always like unbounded solutions too but if you try to stream a file past a regex-er it is likely to be slow, and as pointed out by others, not even reasonable in the general case although you may want to think about specialized cases that may benefit from any restricted set of regex'es you have. You would have to think about "strategies" or similar notions that look at the problem and pick an approach or specific implementation based on parameters. I originally came here to do 1000's of REGEX queries on megabyte strings and ultimately used Boost and Greta for testing but quickly found ways to compile query/sample vectors and implement restricted searches once I found all the not-so-regular expressions fit a given constraint or could even do simple things like sorts to preserve locality later. There are a lot of potential performance limitations depending on the specific task parameters and machine. But, yes, it would be nice if someone had a general "strategy" library. LOL. > In the worst case, if you're using Perl-style expressions (or any style > that isn't strictly "regular" and requires backtracking; lookahead > assertions are a common culprit), the entire input may have to be > consumed and buffered even if the expression ultimately matches only a > few characters (see "On the Use of Regular Expressions for Searching Text", > Clark and Cormack, ACM Transactions on Programming Languages and Systems, > Vol 19, No. 3, pp 413-426.). Therefore, if you're dealing with small > files, you may as well buffer the entire file in a char array and use > regex_token_iterator. If you're dealing with large files, > memory map the file instead. > > daniel > > _______________________________________________ > Boost-users mailing list > Boost-users(a)lists.boost.org > http://lists.boost.org/mailman/listinfo.cgi/boost-users _________________________________________________________________ Internet Explorer 8 – Get your Hotmail Accelerated. Download free! http://clk.atdmt.com/MRT/go/141323790/direct/01/

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Re: [Boost-users] Using boost regex dll in code
by John Maddock 30 Mar '09

30 Mar '09

> Is there a way to contact you directly? I believe my confusion can be > solved rather quickly w/o using the user groups. You can use the john - at - johnmaddock.co.uk address to mail me directly, but I'll be offline for the day very shortly, Regards, John.

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regex iterator question
by Robert Ramey 30 Mar '09

30 Mar '09

I've got a need for regex and I would like to use it to extract tokens matching a regular expresssion from a file stream. Seems like this would be a common desire. So first shot is boost::regex_token_iterator<some_input_iterator> This doesn't work since regex_token_iterator requires a bidirectional iterator. Seems reasonable enough. So next I comb through boost and find #include <boost/spirit/iterator/multi_pass.hpp> and try boost::regex_token_iterator< boost::spirit::multi_pass<some_input_iterator> > I'm thinking this is veeeeeery cool - maybe a 1000 lines of free code included for the price of one. But, doesn't work. multi_pass is a forward_trasversal iterator while regex_token_iterator requires a bidirectional_trasversal_iterator. A huge disappoint to come soooo close. Thinking about it, this problem must come very often. How is it usually addressed? There must be a simple bridge across this. In a pinch, I'll just have to load the whole file into some sort collection, but I prefer the ultimate unlimited file size solution. Robert Ramey

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boost.statechart - a data driven state machine
by dev＠kostiadis.com 30 Mar '09

30 Mar '09

Hello all, I'm using the statechart library to create a generic state machine that I can reuse in a number of projects. I'd like this state machine to be completely data driven because it will massively simplify testing and experimenting with different behaviours (i.e. I won't have to re-compile and produce new executables to try out a simple change). Instead of hard-coding all the states, events, transitions, etc., I would like to read all those in from a config file (text, csv, xml, whatever). I'm pretty sure I can't be the first person to want this. Is there an implementation of this out there somewhere? Are there any docs/links/etc. that will point me to the right direction? Thank you in advance, k.

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Problem using Boost->String->Split
by professor rumsdiegeige 30 Mar '09

30 Mar '09

Hello, using Visual Studio 2005 and Boost 1.31, I'm trying to compile this: #include <boost/algorithm/string.hpp> #include <boost/algorithm/string/split.hpp> #include <vector> #include <string> using namespace boost::algorithm; typedef vector< string > split_vector_type; split_vector_type SplitVec; std::string r = std::string(sc); boost::algorithm::split( SplitVec, r, boost::algorithm::is_any_of(sep) ); But I get: error C2039: 'iterator': is not a member of "global namespace'' in iterator.hpp 37 What's wrong here? Thanx! Sabine Lorentz

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Re: [Boost-users] Using boost regex dll in code
by John Maddock 30 Mar '09

30 Mar '09

> If I have the boost_regex 1_38 dll and lib for VC 8, what steps do I need > to > take in order to use it in my code? Is there anything else that I need > other than one of those? The headers would be a good start :-) You will need to define BOOST_REGEX_DYN_LINK when building so that the regex lib knows to import code from a dll, otherwise the default is for it to expect to static link. And also note that there are two dll's for VC8, one for the debug runtime and one for the release runtime. HTH, John.

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