November 2013 - Boost - lists.preview.boost.org

Any interest in a framework for memoization?
by Giacomo Drago 14 Dec '13

14 Dec '13

Hi, I would like to submit a small framework for memoization I am working on (http://projects.giacomodrago.com/c++memo/). At the moment, it is still in a beta stage and does not comply with Boost guidelines. I would like to know if you might be interested. The idea is to have a tool for rapid prototyping of software components implementing dynamic programming algorithms or, anyhow, requiring memoization. I paste here a simple "fibonacci" example: ---------------------- int fibonacci(int i, std::function<int(int)> prereqs) { if (i == 0) return 0; if (i <= 2) return 1; return prereqs(i-1) + prereqs(i-2); } cppmemo::CppMemo<int, int> cppMemo; std::cout << cppMemo.getValue(30, fibonacci) << std::endl; ---------------------- The code will print 832040, without recursive calls to the "fibonacci" function. A stack is managed "under the hood" and appropriate calls are made to the "fibonacci" callback to gather pre-requirements and then call the function again when they are available. This is just a toy example. There is more to know about, including important caveats (if you are interested, please read the documentation carefully): some defaults for template and method parameters are useful for conciseness but are EVIL if you don't know about them. The framework also provides automatic parallelization (when possible). It is important to remark that at this moment the framework relies on fcmm (fast concurrent memoization map), a custom hashmap that is optimized for this very purpose. This can be changed quite easily, as fcmm is not exposed to the client. A C++11 compliant compiler is needed. Thanks for your attention. Giacomo

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[build] Default compiler options for a toolset
by Edward Diener 10 Dec '13

10 Dec '13

How are the default compiler options for a toolset chosen ? Is it in the .jam file for the compiler toolset and, if so, where is it specified ?

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BOOST_NO_CXX11_ATOMIC?
by Peter Dimov 04 Dec '13

04 Dec '13

Now is perhaps not a very appropriate time to ask, but why don't we seem to have a macro for the <atomic> C++11 header?

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[IdentityType] Const omission undocumented.
by Mostafa 03 Dec '13

03 Dec '13

#include <boost/utility/identity_type.hpp> #include <utility> int main() { BOOST_IDENTITY_TYPE(( std::pair<int,int> const )) x; // This compiles, so the const qualification in the // above macro parameter is ignored. x = std::make_pair(0,1); return 0; } The omission of const qualification in BOOST_IDENTITY_TYPE types is undocumented. This omission maybe deduced from the documented implementation, but, as noted, that is not part of the library api and is subject to change. I therefore propose that this behaviour be documented as part of the library's public api. Mostafa

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Subversion repository closed for all commits on all branches
by Beman Dawes 02 Dec '13

02 Dec '13

The Subversion repository is now closed for all commits on all branches. An attempt to commit will fail a pre-commit hook, resulting in the following error message: Command: Commit Modified: C:\boost\trunk\libs\system\doc\index.html Sending content: C:\boost\trunk\libs\system\doc\index.html Error: Commit failed (details follow): Error: Commit blocked by pre-commit hook (exit code 1) with output: Error: This Subversion repository is no longer in active use. Error: Error: It has been superseded by a Git super-project repository Error: and individual Git repositories for each Boost library. Error: Error: See: https://github.com/boostorg Completed!: The next step in the conversion to Git and Modular Boost is to run the conversion script one last time, and then turn it off. We will let you know when that is completed. -- The Release Managers

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[conversion] Isolating the phantom file changes problem
by Beman Dawes 01 Dec '13

01 Dec '13

This is the simplest case I could come up with where git clone produced a initially modified state. Any ideas why this is happening? Is this another manifestation of crlf problems? --Beman D:\modular-boost\libs\intrusive>git clone --recursive git@github.com:boostorg/boost.git modular-boost ... much output, no apparent error messages... D:\modular-boost>git status # On branch master # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # (commit or discard the untracked or modified content in submodules) # # modified: libs/interprocess (modified content) # modified: libs/intrusive (modified content) # modified: libs/pool (modified content) # no changes added to commit (use "git add" and/or "git commit -a") D:\modular-boost>cd libs/pool D:\modular-boost\libs\pool>git status # Not currently on any branch. # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: doc/images/mb1.svg # modified: doc/images/mb2.svg # modified: doc/images/mb3.svg # modified: doc/images/mb4.svg # modified: doc/images/pc1.svg # modified: doc/images/pc2.svg # modified: doc/images/pc3.svg # modified: doc/images/pc4.svg # modified: doc/images/pc5.svg # no changes added to commit (use "git add" and/or "git commit -a") D:\modular-boost\libs\pool>cd ..\interprocess D:\modular-boost\libs\interprocess>git status # Not currently on any branch. # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: proj/vc7ide/managed_shared_memory.vcproj # modified: proj/vc7ide/offset_ptr_test.vcproj # no changes added to commit (use "git add" and/or "git commit -a") D:\modular-boost\libs\interprocess>cd ..\intrusive D:\modular-boost\libs\intrusive>git status # Not currently on any branch. # Changes not staged for commit: # (use "git add <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: proj/vc7ide/avl_multiset/avl_multiset.vcproj # modified: proj/vc7ide/avl_set/avl_set.vcproj # modified: proj/vc7ide/sg_multiset/sg_multiset.vcproj # modified: proj/vc7ide/sg_set/sg_set.vcproj # modified: proj/vc7ide/splay_multiset/splay_multiset.vcproj # modified: proj/vc7ide/splay_set/splay_set.vcproj # no changes added to commit (use "git add" and/or "git commit -a")

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An open typeswitch using lambdas
by Sumant Tambe 30 Nov '13

30 Nov '13

Hi, I would like to get feedback on a small typeswitch library I've been working on for some time now. The library is designed to dispatch code (lambdas) based on the actual value of boost::any, boost::variant, and also general polymorphic hierarchies. An example is in order. template <class Poly> void test_poly(Poly& p) { match(p)( [](int i) { std::cout << "int = " << i << "\n"; }, [](double d) { std::cout << "double = " << d << "\n"; }, [](const std::string &s) { std::cout << "string = " << s << "\n"; }, [](std::ostream &o) { std::cout << "found ostream" << "\n"; } ); } int main(void) { std::ios_base &stream = std::cout; boost::any any(std::string("C++ Truths")); boost::variant<int, std::string> var("boost"); double d = 9.99; test_poly(stream); // prints found stream test_poly(any); // prints string = C++ Truths test_poly(d); // prints double = 9.99 test_poly(var) // prints string = boost } The implementation of the library is a little over 250 lines. Check it out here: http://coliru.stacked-crooked.com/a/72597a93b12916d4. clang is the only compiler I've been able to compile it with. It resembles Scala's match statement. Scala's match is way more powerful than what I've been able to achieve with C++ library emulation. It is also quite similar to Stroustrup's "Open and Efficient Typeswitch for C++" ( http://www.stroustrup.com/OOPSLA-typeswitch-draft.pdf) A quick benchmark shows that lambda-based typeswitch is about 4 to 5 times *slower*. If there is sufficient interest, I would be thrilled to contribute this library to boost. I believe it can be further generalized to support n-ary method dispatching. Thoughts? R/ Sumant

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[git] Line endings in bootstrap.bat on Windows
by Björn Pollex 29 Nov '13

29 Nov '13

I just cloned the modularized Boost repository from Github [1]. Right after the clone is done, git status gives me a complete diff on bootstrap.bat (so probably line endings). I do have autocrlf = true in my system configuration, so this shouldn't be the problem, right? Is anyone else seeing this? Am I doing something wrong? If so, how to do it correctly? Regards, Björn Pollex [1] https://github.com/boostorg/boost

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Is there a thin array wrapper/proxy lying around somewhere?
by Mostafa 29 Nov '13

29 Nov '13

(Yes, I'm aware of boost.array, boost.multiarray, and std::vector.) Is there any thin but complete array wrapper/proxy lying around somewhere in boost? A class that if substituted for an array will behave just like the substituted array? Thanks, Mostafa

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Re: [boost] [conversion] Enforcing tabs to spaces conversions and other git goodies.
by Cox, Michael 28 Nov '13

28 Nov '13

Michael On Thu, Nov 28, 2013 at 8:06 AM, Beman Dawes <bdawes(a)acm.org> wrote: > > On Thu, Nov 28, 2013 at 5:00 AM, Mateusz Loskot <mateusz(a)loskot.net> wrote: > > > On 28 November 2013 08:49, Cox, Michael <mhcox(a)bluezoosoftware.com> wrote: > > > In addition to re-normalizing the line endings, we could also start > > > enforcing coding standards, e.g. tabs converted to spaces standard via > > > gitconfig/gitattribute filters. Git allows you to define filters in your > > > .git/config or ~/.gitconfig file and specifying their use in > > > .gitattributes, e.g. in .gitconfig: > > > > > > # Convert tabs to 4 spaces (uses Linux expand/unexpand commands, so not > > > cross-platform) > > > [filter "tabspace"] > > > smudge = unexpand --tabs=4 --first-only > > > clean = expand --tabs=4 --initial > > > [...] > > > > ...automatically behind the scene? Scary! > > > > IMHO, this belongs to commit hooks. > > > > Qt's sanitize-commit may be a good example > > > > https://qt.gitorious.org/qt/qtrepotools/source/b69da7d675774be14027808328ea… > > > > Michael and Mateusz, > > Yes - sanitizing and commit hooks are important topics. But the way to > handle them is to start a new thread so that they don't get lost in the > line-ending bicycle shed discussion. > > Thanks, > > --Beman Mateusz, I agree hooks have to be used for the "golden" boostorg repositories since folks may forget to configure their local/public repositories with the appropriate hooks/filters, but if Boost goes fully distributed like Linux, there may be a lot of integration repositories a change flows through on it's way to boostorg and it's probably best to get the code normalized as soon as possible. Michael

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