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how to get started? (not in documentation)
by Tom Weber 01 Jan '04

01 Jan '04

Hello, I downloaded boost today so regard me as a newbie. Boost seems great, but the documentation doesn't mention how I should install boost on my system (redhat 9), and how to link against the built libraries. Sure I can include it in every project (though it's huge!), and make the makefiles link into strange locations such as libs/test/build/bin/libboost_unit_test_framework.a/gcc/debug/runtime-link-static/threading-single/libboost_unit_test_framework.a Is there an easier way? Why aren't packages like boost-[devel-]VERSION.PLATFORM.rpm made? Why aren't all built libraries put in the same directory, with a simple path name? Why isn't the thread library built statically? Is putting a "lib" section with BOOST_THREAD_BUILD_STATIC=1 in the Jamfile a legal fix? (seems to work) Also... I think boost should have a network library. Can anyone recommend a platform-independent network library? I'm thankful for any answer... -- Cheers, Tom Weber http://www.dd.chalmers.se/~np98towe/

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using regex for in-place string modification
by Scott Meyers 29 Dec '03

29 Dec '03

I want to use regex to modify a string in place. In particular, I've read the contents of a file into a string, now I want to do some search/replace functions on the string, then write the modified string back out to the original file. I've looked through the regex documentation, including the October 2001 DDJ article, but I don't see any way to modify a string in place. From what I can tell, regex_merge looks like it does the kind of thing I want, except it doesn't seem to modify in place. I'd prefer to avoid creating two strings of each file's contents, one before regex processsing, one after. Is there functionality in regex that will let me modify a string in place? Thanks, Scott

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problem with regex_fwd.hpp
by Stefan Shishkov 29 Dec '03

29 Dec '03

Hi, I had a small problem using boost::regexp on MS VC 6.0, boost 1.30.2. In one of my headers I included regex_fwd.hpp. The compilation failed with: ..\boost-1.30.2\boost/detail/allocator.hpp(215): error C2065: 'assert': undeclared identifier Allocator.hpp does not include <cassert> probably relying that it will be included before it. I solved this problem by including <cassert> before regex_fwd.hpp but may be it is better to change allocator.hpp? Or probably something is wrong with my configuration? Best regards Stefan

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error C2668 with <boost/regex.hpp>
by Yiftah Frechter 28 Dec '03

28 Dec '03

Hi guys, I'm trying to use boost regex with VC6 Receiving the following error: error C2668: 'sprintf' : ambiguous call to overloaded function there is no "using namespace std" in my code. Appreciate any help. Yiftah

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undirected graph cycle
by magh＠lehigh.edu 27 Dec '03

27 Dec '03

Is there any easy way to use DFS visitors to return a cycle in an undirected graph? The examples show how to detect if a cycle exists. How do you actually extract it? For my instance, I am dealing with an undirected graph that is a 1-tree, i.e., I know there is exactly one cycle. Thanks, Matt ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/

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date_time: number of days between dates
by Lars Schouw 25 Dec '03

25 Dec '03

I found a solution: long no_days(boost::gregorian::date d1, boost::gregorian::date d2) { using namespace boost::gregorian; using namespace boost::posix_time; date_period dp(d1, d2); return dp.length().days(); } --------------------------------- Do you Yahoo!? Yahoo! Photos - Get your photo on the big screen in Times Square

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date_time converting from date to number of days
by Lars Schouw 24 Dec '03

24 Dec '03

I want to find the number of days in-between two days. What is the easiest way to do this? I am using the date_time lib and want to find the number of days from the time_t started. ptime timet_start(date(1970,1,1)); ptime t(d); time_duration diff = t - timet_start; ptime t123(diff); // timeval tv; //drop off the fractional seconds... // tv.tv_sec = diff.ticks()/time_duration::rep_type::res_adjust(); return 0; // return difference.days; Lars Schouw --------------------------------- Do you Yahoo!? Yahoo! Photos - Get your photo on the big screen in Times Square

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lexical_cast and whitespace, part 2
by Miro Jurisic 18 Dec '03

18 Dec '03

I was trying to do the following: class MyString; std::istream oprator>>(std::istream&, MyString&); std::string s1 = "Hello, World"; MyString s2 = lexical_cast <MyString> (s); It doesn't work. The reason for it failing is: a. the semantics of operator>>(std::istream&, MyString&) are identical to the semantics of operator>>(std::istream&, std::string&) b. the semantics of operator>>(std::istream&, std::string&) are to read the stream up to the first whitespace (as per the stream locale) c. lexical_cast uses (via lexical_stream) operator>>(std::istream&, MyString&) to read the data into MyString The upshot of this is that lexical_cast writes "Hello, World" to the stream (via operator<<(std::ostream&, const std::string&)), reads off "Hello," to MyString (via operator>>(std::istream&, MyString&)), and then throws a bad lexical_cast after noticing there's data left on the stream. The natural question is why it is that this works when converting to a std::string; it seems that it should have the same problem. The answer is that boost::detail::lexical_stream has a lexical_stream::operator>>(std::string&) which ignores whitespace, thus working around the problem if (and only if) the target type of the cast is std::string. Attempting to use lexical_cast with any string type other than std::string fails when the source data contains (non-trailing) whitespace. This is suboptimal. I am going to try a workaround shortly, by partially specializing lexical_stream, but that's just a workaround. I don't see any way to do this without a. breaking the lexical_cast abstraction barrier (as I am about to do) or b. making the semantics of operator>>(istream&, MyString&) differ from those of operator>>(istream&, std::string&) I don't think either of those is the rigt answer. Is there one? Shouldn't there be one? Thanks, meeroh

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Problems with Multi Threaded Version
by Zeros and Ones 18 Dec '03

18 Dec '03

So far I was using the Single Threaded Run Time Library and had no trouble with Boost, however I switched to useing the Run Time Versions just now and found that nothing seemed to work and the error that I get is: "Boost_Regex_vc7_mdid.dll was not found. Re-installing the application may fix this problem" However, the instructions on the website state : "Finally when you use regex++ it is only necessary for you to add the <boost> root directory to your list of include directories for that project. It is not necessary for you to manually add a .lib file to the project; the headers will automatically select the correct .lib file for your build mode and tell the linker to include it. " Im using VC7, and I cant understand why I get this error, do I need to change some setting while linking to the multi threaded versions? For now, I copied the two dll's _boost_regex_vc7_mdid.dll and _boost_regex_vc7_mdi.dll to my working directory and I have a working application, but Im foxed and I would like to know what im doing wrong! Thanks. "Zeros Bits and Bytes"

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BGL and reversing / moving edges
by joshrose 17 Dec '03

17 Dec '03

G'day, I was hoping someone might be able to tell me if they've run into any situations using BGL where they needed to move (or reverse (i.e. flip the source and target)) an edge within a graph implemented as an adjacency_list. I'm working on an implementation of an algorithm for max. weight bipartite matching ("the assignment problem"), and one of the assumptions in the algorithm is that non-matched edges are directed from one subgraph, A, to the other subgraph, B, and matched edges are directed the other way. Over the course of growing the matching, a simple way to add and remove edges from the candidate set is just to reverse the edge, thus the need for some way to reverse the edge within BGL. I don't think I can just remove and then re-add the edge in the other direction, primarily because doing so will (I believe) invalidate any edge_descriptors referring to that edge. In particular, there are property maps keeping track of the weight of edges, the predecessors of certain nodes, etc. that use edge descriptors as keys. I've spent a fair bit of time reading the documentation and looking through the implementation of adjacency_lists (incl. edge_list_impl), and I'm not really sure of a way to either move an edge directly within a graph, or even to create a new edge from another s.t. they have the same edge_descriptor (in general a bad thing, probably). Anyone have any thoughts on this? Thanks, -Josh

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