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RE: [Boost-Users] Q: Boost Python / weave / swig
by Aleksey Gurtovoy 13 Nov '02

13 Nov '02

Claudius Schnörr wrote: > I would like to build a python-interface for a C++-template library I > wrote. > > After looking around a bit, besides Boost-python I found swig > and weave, which seem to have a similar purpose in mind!?! > > I would appreciate it if someone could provide some comparing > hints/links/information about these various solutions (I'm new to all > these packages). > How do they differ in terms of > - the learning curve, > - their capabilities and > - their foci ? > Have you seen this one - http://www.boost.org/libs/python/doc/comparisons.html? It's more than 1 year old, though, so things might have changed since then. In general, it's better to ask Boost.Python-related questions here - http://mail.python.org/mailman/listinfo/c++-sig. For one, you are much likely to get a quicker response :). Aleksey

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Can not gunzip bjam.exe.gz
by Mike Wilson 13 Nov '02

13 Nov '02

Hi, In Cygwin (version 2.125.2.10) I've tried to $ gunzip bjam.exe but get gunzip: bjam.exe.gz: not in gzip format (downloaded http://boost.sourceforge.net/jam-executables/bin.cygwinx86/bjam.exe.gz which was 143,050 bytes in size (x3 tries) ) My WinZip (V8.1) can't read it either. In fact I can't seem to read several of the .gz files that can be downloaded (but I did manage the Windows .zip version). Can anybody give me a clue as to what is wrong ? Mike Wilson

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Erasing an element in shared_ptr
by cadiolis 12 Nov '02

12 Nov '02

I know that the destructor of shared_ptr will call delete for its contents, but what about erasing a member using the standard erase() function in vector?

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RE: [Boost-Users] set thread priority
by Mark Storer 12 Nov '02

12 Nov '02

I'd think a relatively simple implementation would be to simply support them when possible, and otherwise turn all such calls into no-ops. Coming up with a range of priority values that would be portable shouldn't be too terribly difficult either. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard;

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using ublas to solve linear systems?
by deane_yang 12 Nov '02

12 Nov '02

I'm trying to see if I can use ublas to solve a linear system of equations. Digging through the documentation, I find a description of a function called 'solve" that says "Solves a linear equation for a triangular matrix." There is also a formula, B = solve(A, B, tag) <------> B <- A-1 B But I just don't know what any of this means (even though I am a mathematician and quite fluent in linear algebra). So a) can ublas be used (without me implementing any additional algorithms) to solve a linear system of equations? b) what exactly does the function solve do?

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RE: [Boost-Users] BUG: counted_base::release
by Per Kristensen 12 Nov '02

12 Nov '02

This is a constructed test case which should illustrate the problem. The bug is only a problem if you access data members of the counted_based object after the call to delete. So you can live happy without knowing anything about the bug if you never do that. //sourcecode begin #include "boost/shared_ptr.hpp" #include "boost/weak_ptr.hpp" class foo { public: void setWeak(boost::shared_ptr<foo> s) { w = s; } private: boost::weak_ptr<foo> w; //the desctuction of this member will delete the counted_based object }; class deleter { public: deleter() :lock(0) {} ~deleter() { assert(lock==0); //assert if destructor is called when we are executing } void operator() (foo *p) { ++lock; //lock the object from destruction within this operation delete p; --lock;//unlock the object } private: int lock; }; void main() { boost::shared_ptr<foo> s(new foo,deleter()); s->setWeak(s); s.reset(); } //source code end -----Original Message----- From: Peter Dimov [mailto:pdimov@mmltd.net] Sent: 11. november 2002 21:43 To: Boost-Users(a)yahoogroups.com Subject: Re: [Boost-Users] BUG: counted_base::release From: "perkristensennettest" <per.kristensen(a)nettest.com> > To me it seems like a bug, that the weak_count in > counted_base::release is decremented before the call to dispose. See > below [...] > > If the call to dispose() indirectly calls weak_release there is an > error as weak_release will decrement the --weak_count and may > destruct the counted_base object. This will happen if you have an > class C with a member of type weak_ptr<C>. Do you have a test case that breaks? 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 the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> . [Non-text portions of this message have been removed]

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uBLAS Matrix Multiplication
by Hickman, Greg 12 Nov '02

12 Nov '02

Why isn't there an overloaded matrix_expression operator* (const matrix_expression&, const matrix_expression&); for peforming matrix multiplication? Greg Hickman

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compose function objects
by daniel szymanski 11 Nov '02

11 Nov '02

hi, i've a question regarding the compose function objects. i was wondering if there is something like compose_f_x_gy etc? i know there's only the compose_f_gx_hy function object. but then i would need g(x) = x, so my question: is there another way to get the same result like using g(x) = x or writing a compose_f_x_gx? thanks, daniel

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RE: [Boost-Users] compose function objects
by Mark Storer 11 Nov '02

11 Nov '02

I'd think you could write a toy function (inline and all that) to do just that, then pass it in as the 'gx' param. I'd be disappointed if it didn't vanish during optimization, leaving just the 'x'. --Mark Storer Software Engineer Cardiff Software #include <disclaimer> typedef std::disclaimer<Cardiff> Discard;

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BUG: counted_base::release
by perkristensennettest 11 Nov '02

11 Nov '02

To me it seems like a bug, that the weak_count in counted_base::release is decremented before the call to dispose. See below //source code begin void release() // nothrow { long new_use_count; long new_weak_count; { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif new_use_count = --use_count_; new_weak_count = --weak_count_; //this is a bug } if(new_use_count == 0) { dispose(); //the this object may be deleted here } if(new_weak_count == 0) { // not a direct 'delete this', because the inlined // release() may use a different heap manager self_deleter_(this); } } //source code end If the call to dispose() indirectly calls weak_release there is an error as weak_release will decrement the --weak_count and may destruct the counted_base object. This will happen if you have an class C with a member of type weak_ptr<C>. As I see it the decrement of weak_count should be moved to after the dispose call. see below: //source code begin void release() // nothrow { long new_use_count; long new_weak_count; { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif new_use_count = --use_count_; //do not decrement weak_count here } if(new_use_count == 0) { dispose(); } { #ifdef BOOST_HAS_THREADS mutex_type::scoped_lock lock(mtx_); #endif new_weak_count = --weak_count_; } if(new_weak_count == 0) { // not a direct 'delete this', because the inlined // release() may use a different heap manager self_deleter_(this); } } //source code end ????

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