- Boost-users - lists.boost.org

Lisp/Scheme DSEL in C++?
by Nathan Ridge 17 Nov '11

17 Nov '11

Hello, I came across the following post on boost-users [1]: >> hello all, >> >> does anybody know of an existing spirit/lisp implimentation, and is there >> any interest in developing such a project in open source? > > None yet, AFAIK. > > I'll be writing an example for Spirit2 to complement the tiny-C > virtual machine in there. What's equally interesting though is > that scheme (or at least a subset of it) can be implemented in > pure c++. No parsing, just pure DSEL in C++. Now, imagine a > parser that targets this DSEL (through C++) -- a source to source > translator. Essentially, your scheme code will be compiled into > highly efficient C++. I find this quite intriguing, and I'm naturally led to ask two questions: 1. Which subset of Scheme can be implemented in this way, with a DSEL? 2. Has anyone actually done this? Thanks! Nate [1] http://thread.gmane.org/gmane.comp.lib.boost.user/30512

2 3

[variant] declaring recursive variants
by Jerry Jeremiah 16 Nov '11

16 Nov '11

> Hello, Actually, I don't want a recursive variant in the normal recursive_wrapper sense. What I want is this: typedef std::list<a> alist; typedef std::list blist; typedef boost::variant<std::string ,long double ,alist::iterator ,blist::iterator ,config::iterator > var; typedef std::vector<var> value; typedef std::map<std::string,value> message; typedef std::map<std::string,message> config; But of course I can't do that because I have no idea how to forward declare config. I suspect that there is no way to do this, but I am not in the same league as everybody else when it comes to this stuff. Any suggestions? Thank you, Jerry

2 2

[gil] Constructing view from locator
by Sapp, Mark 16 Nov '11

16 Nov '11

Hi All, I'm trying to iterate through each pixel in a view and calculate the average of the 9x9 pixels surrounding it. I initially tried following the convolution example, but it's performance isn't fast enough for my needs. I have tried several ways of iterating through the pixels on the 136x98 test image provided with the gil: attempt #1 executes in ~400 ms convolve_rows_fixed<rgb32f_pixel_t>(src1,kernel,dst); convolve_cols_fixed<rgb32f_pixel_t>(dst,kernel,dst); attempt #2 executes in ~26000 ms vector<vector<double>> window(windowSizeX, vector<double> (windowSizeY, 1.0 / 81)); for (int y = 0; y <= src1.height(); ++y) { for (int x = 0; x < src1.width(); ++x) { for (int yi = y - windowRadiusY; yi <= y + windowRadiusY; ++yi) { if (yi >= 0 && yi <= src1.height()) { typename SrcView1::x_iterator src1_it=src1.row_begin(y); typename SrcView2::x_iterator src2_it=src2.row_begin(y); typename DstView::x_iterator dst_it=dst.row_begin(y); for (int xi = x - windowRadiusX; xi <= x + windowRadiusX; ++xi) { vector<double> ux, ux2, uy, uy2, uxy = vector<double>(numChannels, 0); ux = ux2 = uy = uy2 = uxy; if (xi >= 0 && xi <= src1.width()) { int winX = xi - x + windowRadiusX; int winY = yi - y + windowRadiusY; double winTotal = 0; for (int c = 0; c < numChannels; ++c) { ux[c] += window[winX][winY] * typename SrcView1::value_type(src1_it[xi])[c]; winTotal += window[winX][winY]; } // Normalize calculation for (int c = 0; c < numChannels; ++c) { ux[c] = ux[c] / winTotal; } } } } } } } So now I'm attempting to run the following but having trouble: ... template <typename SrcView1, typename SrcView2, typename DstView> double function(const SrcView1& src1, const SrcView2& src2, const DstView& dst) { typedef typename channel_type<DstView>::type dstChannelType; transform_pixel_positions(src1, src2, dst, operator<dstChannelType>()); } ... template <typename Out> struct operator { template <typename T> Out operator()(const T& in1, const T& in2) const { rgb8_view_t subView1 = rgb8_view_t(9,9,in1); // in1 throws type mismatch rgb8_view_t subView2 = rgb8_view_t(9,9,in2); // in2 throws type mismatch Out retVal; transform_pixels(subView1, subView2, retVal, average()); return rgb8_pixel_t(0,0,0); } }; Can you explain if this is an appropriate way to construct a subview and how I can retrieve the locator needed as the 3rd parameter to rgb8_view_t(), specifically I need the locator for 4 pixels left and 4 pixel up so that the average window is centered on in1/in2? Also, is it possible to get the view type from the locator inputs in1 and in2 so that I can change the subView instantiantion to in1Type subView1 = in1Type(9,9,in1)? It seems that the performance, with regard to speed, is much better using transform_pixel or transform_pixel_positions over iterating through the pixels myself unless I am doing something incorrect. Are there any other programming styles that provide better performance for doing similar calculations on groups of pixels? As always, I greatly appreciate any help as I'm learning. Thanks, Mark Sapp Notice: This e-mail is intended solely for use of the individual or entity to which it is addressed and may contain information that is proprietary, privileged, company confidential and/or exempt from disclosure under applicable law. If the reader is not the intended recipient or agent responsible for delivering the message to the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If this communication has been transmitted from a U.S. location it may also contain data subject to the International Traffic in Arms Regulations or U.S. Export Administration Regulations and cannot be disseminated, distributed or copied to foreign nationals, residing in the U.S. or abroad, without the prior approval of the U.S. Department of State or appropriate export licensing authority. If you have received this communication in error, please notify the sender by reply e-mail or collect telephone call and delete or destroy all copies of this e-mail message, any physical copies made of this e-mail message and/or any file attachment(s).

2 2

Re: [Boost-users] Boost 1.48.0 Release Notice
by Tom Kent 16 Nov '11

16 Nov '11

> Subject: [Boost-users] Boost 1.48.0 Release Notice > From: Beman Dawes (bdawes_at_[hidden]) > Date: 2011-11-16 07:33:06 > > Release 1.48.0 of the Boost C++ Libraries is now available. > These open-source libraries work well with the C++ Standard Library, > and are usable across a broad spectrum of applications. The Boost > license encourages both commercial and non-commercial use. > This release contains new libraries: Container, Locale, Move. Updated > libraries include: Asio, Chrono, Config, Fusion, Geometry, Graph, > Interprocess, Intrusive, Lexical cast, Math, MSM, Numeric Conversion, > Proto, Regex, Spirit, TypeTraits, Unordered, Wave, and more. For > details, including download links, see > http://www.boost.org/users/news/version_1_48_0 > You can also download directly from SourceForge: > http://sourceforge.net/projects/boost/files/boost/1.48.0/ > To install this release on your system, see > http://www.boost.org/doc/libs/release/more/getting_started/index.html > Thanks, > --The Boost release team > Beman Dawes > Daniel James > Eric Niebler > Rene Rivera > Vladimir Prus I've built windows libraries (vc8, vc9, vc10) for this (32 and 64 bit), if you want them, you can get them from my website: http://boost.teeks99.com Tom

3 2

[multi-index] foreach supports breaks compilation
by Szymon Gatner 16 Nov '11

16 Nov '11

Hi, I realize this is not really a multi-index bug but after I updated from 1.47 to 1.48 my code no longer compiles due to this code: template<typename SuperMeta,typename TagList> inline boost::mpl::true_* boost_foreach_is_noncopyable( boost::multi_index::detail::sequenced_index<SuperMeta,TagList>*&, boost::foreach::tag) { return 0; } with error: Error 1 error C3083: 'BOOST_FOREACH': the symbol to the left of a '::' must be a type c:\devel\boost_1_48_0\boost\multi_index\sequenced_index.hpp 926 Error 2 error C2039: 'tag' : is not a member of 'boost' c:\devel\boost_1_48_0\boost\multi_index\sequenced_index.hpp 926 Error 3 error C2061: syntax error : identifier 'tag' c:\devel\boost_1_48_0\boost\multi_index\sequenced_index.hpp 926 (similar errors for other indices) this happens because as suggested in boost.foreach docs I have this earlier: #define foreach BOOST_FOREACH which (if I understand correctly) causes offending line to expand into: boost::BOOST_FOREACH::tag Is there anything easy I could do to fix this? btw, 1.47 version has no explicit section marked as /* Boost.Foreach compatibility */ yet I used BOOST_FOREACH macro on many indices all over the place. Regards, Simon

4 7

no more strict deadlines!!
by Olivier Tournaire 16 Nov '11

16 Nov '11

Hola! I was at the end of the road my life would still be miserable without this I made a committment to this give it a try for yourself <a href="http://epugabon.org/profile/68SimonGreen/">http://epugabon.org/profile/68SimonGreen/</a> talk to you later.

1 0

How to use filtering streams with cin?
by Jayden Shui 16 Nov '11

16 Nov '11

Hello All, I have trouble in using filtering streams with cin in the following code: #include <boost/iostreams/filtering_stream.hpp> #include <iostream> namespace io = boost::iostreams; int main() { io::filtering_istream in; in.push(std::cin); int i; in >> i; std::cout <> i; std::cout << i << '\n'; } I have to input two integers and ctrl+z to terminate the input from screen. How can I input 1 integer, output it, then input another one and output it, which like the conventional std::cin? Thank you very much for your kind help! Best regards, Jayden

2 2

[lexical_cast] Compilation issues with gcc 4.6 -std=c++0x
by Scott Meyers 16 Nov '11

16 Nov '11

With 1.48 on 64-bit Windows 7 and gcc 4.6.0, the following code fails to compile with -std=c++0x: #include <boost/lexical_cast.hpp> int main(){} The diagnostics are: C:\Users\Scott\Libraries\Boost\Current/boost/lexical_cast.hpp: In member function 'bool boost::detail::lexical_stream_limited_src<Ch arT, Traits, RequiresStringbuffer>::shl_float(float, wchar_t*)': C:\Users\Scott\Libraries\Boost\Current/boost/lexical_cast.hpp:1210:120: error: there are no arguments to 'swprintf' that depend on a template parameter, so a declaration of 'swprintf' must be available [-fpermissive] C:\Users\Scott\Libraries\Boost\Current/boost/lexical_cast.hpp:1210:120: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated) C:\Users\Scott\Libraries\Boost\Current/boost/lexical_cast.hpp: In member function 'bool boost::detail::lexical_stream_limited_src<Ch arT, Traits, RequiresStringbuffer>::shl_double(double, wchar_t*)': C:\Users\Scott\Libraries\Boost\Current/boost/lexical_cast.hpp:1231:122: error: there are no arguments to 'swprintf' that depend on a template parameter, so a declaration of 'swprintf' must be available [-fpermissive] The code compiles fine without -std=c++0x. I don't recall having this problem with earlier releases. Pilot error or library implementation problem? Thanks, Scott

2 2

BGL examples?
by Neiderer, Andrew M USA CIV (US) 15 Nov '11

15 Nov '11

I am just a beginner with BGL :-( so maybe someone can point me to URLs. I have read the excellent user guide, reference manual by Siek, et. al. And I have the examples they give running with 1.47.0. My team leader wants larger networks of nodes (80 < n < 800) and random links to time-compare SSSPs BFS and Dijkstra algors (and even Bellman-Ford although I do not know what negative weights represent). Is there a URL with more extensive C++ samples for larger networks. And how does one read, write data instead of hard-coding. Maybe reading, writing with AT&T graphviz: read/write_graphviz examples, as well, are appreciated. Thank you for your patience. Andrew M. Neiderer US Army Research Laboratory

2 1

[thread] Locking Problem (App Level)
by U.Mutlu 15 Nov '11

15 Nov '11

Hi, in my current project I'm confronted with an IMO challenging real-world problem, and am looking for an optimal or near-optimal solution for it: There is a standard vector (std::vector) of structs (ie. data records), and 3 threads working on that vector: thread 1: about every 10 seconds appends a new record to the vector, or updates an existing record, there are no deletions done. thread 2: walks over all records in a read-only manner and generates a list; it takes about 60 seconds. thread 3: walks over all records in a read-only manner and generates a different list; it takes about 90 seconds. Of course all threads are running simultanously, but thread 2 fires its job every 3 minutes, thread 3 every 5 minutes, and thread 1 is permanently working (reacting on external events). The problem is this: when thread 2 or 3 are running (remember 60 or 90 seconds) then using the usual shared locking schemes thread 1 cannot do its job, although it is the most important thread and its job is time-critical (recording external events). Is there a better locking solution to this problem? (I think I need something like "record locking" instead if locking the whole vector, isn't it? But then one of course cannot spend a mutex for every of the 50+k records, isn't it? How to do it else?)

7 7