- Boost - lists.boost.org

[python] can I stop iteration without exception being thrown?
by Gennadiy Rozental 11 Jun '08

11 Jun '08

Hi, I an using vector_indexing_suite for both standard containers export and for our in-house ones. I've noticed that boost::python::error_already_set is bwing thrown every time iteration in python over container instances is about to finish. The exception is ignored somewhere inside boost::python but it's still quite inconvenient for debugging: I want to catch actual error, but can't skip 100s of fake ones. Is there any reason why it was designed this way? Is there any way to avoid it? Gennadiy

6 14

Re: [boost] [circular_buffer] why is there no reserve(size_type)?
by Jan Gaspar 11 Jun '08

11 Jun '08

it is called set_capacity(capacity_type) ----- Original Message ---- From: Thorsten Ottosen <thorsten.ottosen(a)dezide.com> To: "boost(a)lists.boost.org" <boost(a)lists.boost.org> Sent: Wednesday, 11 June, 2008 2:05:14 PM Subject: [boost] [circular_buffer] why is there no reserve(size_type)? Hi Jan, The headline pretty much says it all. -Thorsten _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost __________________________________________________________ Sent from Yahoo! Mail. A Smarter Email http://uk.docs.yahoo.com/nowyoucan.html

2 1

[circular_buffer] why is there no reserve(size_type)?
by Thorsten Ottosen 11 Jun '08

11 Jun '08

Hi Jan, The headline pretty much says it all. -Thorsten

1 0

Bug in iterator_range when NDEBUG not defined but boost asserts are enabled
by John Reid 11 Jun '08

11 Jun '08

iterator_range.hpp defines is_singular() if NDEBUG is not defined but it calls is_singular through the BOOST_ASSERT macro. Unfortunately it is possible to enable BOOST_ASSERT and have NDEBUG defined which leads to a compilation error. To see this compile the iterator_range.cpp example included with the library with the following defines: gcc -DBOOST_ENABLE_ASSERT_HANDLER -I/usr/local/src/boost-trunk/ -DNDEBUG -c iterator_range.cpp John.

4 3

Using Bind & Lambda
by Robert Jones 11 Jun '08

11 Jun '08

This is my first time posting to this list, so I hope you'll forgive me it my etiquette is awry. I'm new to the Boost libraries, and just learning my way around, guided mainly by Bjorn Karlson's book - any other book recommendations would be most welcome btw, and there a few things I just don't quite get! First - is "boost/lambda/bind.hpp" equivalent to "boost/bind.hpp"? Should it ever be necessary to include both? Second - Is it true that a lambda function is syntactically and semantically the same as a bind finction, eg Given:- int foo( int i ) { return i + 3; } Are these two expressions the same? bind( &foo, _1 ); _1 + 3; Finally (for now!) - why is this wrong? struct A { string identity( string ) const; } a; vector<string> v; for_each( v.begin(), v.end(), cout << bind( &A::identity, a, _1 ) << '\n' ); which is intended to output the return value of A::identity() for each element of v, separated by newlines. Thanks in advance for any guidance! Rob. -- ACCU - Professionalism in programming - http://www.accu.org

5 4

[python] working with raw const pointers
by Gennadiy Rozental 11 Jun '08

11 Jun '08

Hi, In our system there are a lot of pointers to const objects flying around. I've got several problems in this regard. They can be exhibited by the following code snippet: a.cpp : class A{}; void boo1( A const* ) {} void boo2( A* ) {} A const* make_const_a() { return (A const*)0; } A* make_non_const_a() { return (A*)0; } std::vector<A const*> make_vec() { return std::vector<A const*>( 1 ); } .... class_<A,boost::noncopyable>( "A", bp::no_init ); class_<std::vector<A const*> >( "AVec", bp::no_init ) .def( vector_indexing_suite<std::vector<A const*> >() ) ; def( "boo", &boo1 ); def( "boo", &boo2 ); def( "make_const_a", &make_const_a, return_value_policy<reference_existing_object>() ); def( "make_non_const_a", &make_non_const_a, return_value_policy<reference_existing_object>() ); def( "make_vec", &make_v ec ); Problem I. Access to mutable func Following python statement mymodule.boo( mymodule.make_non_const_a() ) seems to call incorrect function boo Problem II. Vector fails completely Following python statements vec = pytoolkit.make_vec(); for e in vec: pass produce TypeError: No to_python (by-value) converter found for C++ type: class A const * Any advise? Gennadiy

1 0

Threaded version
by albert meyburgh 11 Jun '08

11 Jun '08

Is there a threaded version of some of the boost components? For example, calling find on a container should be easily threaded. I realize the user could also easily thread this, but it seems like a trivial thing to just add support for in boost itself.

3 2

[python] frame corruption in python -> c++ -> python scenario
by Gennadiy Rozental 10 Jun '08

10 Jun '08

Hi, I am experiencing strange issue I can't find solution for. Sorry I'll need a bit lengthy explanation to describe it. I am using boost python for both automation and embedding the same time. I wrote trivial unit test module (can't use standard one). It has function check like this: def check( val ): check_impl( val ) def check_impl( val ): ... print "Error at line " + str(sys._getframe(2).f_lineno+1) ... ... This supposedly should produce error line location. And it does. Sometimes. test1.py: ... 8> check( False ) produces: Error in line 8: ... I've noticed though that in some cases line numbers are incorrect. I was able to narrow it down to the single function mymodule.foo() Before this function call line numbers are correct. After it incorrect. foo is a function implemented in c++ and exported using boost.python. I was able further to identify that the line at fault inside function foo implementation is the one invoking python function: void foo() { ... boost::python::object obj = ... obj(); ... } So. Finally the question: Is there way to fix/circumvent this somehow? Thanks, Gennadiy

1 0

boost::decimal ?
by Mårten Rånge 10 Jun '08

10 Jun '08

Is there some work been done on implementing a boost::decimal class? If there isn't my guess is that this would be very useful to C++ programmers out there if boost could provide this (we sure would dance with joy!). I would like to help but frankly I lack the competence on how to implement a decimal class efficiently and with the robustness it needs. A decimal class would be very useful for ERP and Financial systems as in many cases of the typical customers work with the decimal system instead of the binary system. It's hard to motivate for the customers why: 1 -0.2 -0.2 -0.2 -0.2 -0.2 doesn't add up to _exactly_ 0 when using double (windows calc.exe had this problem many years ago and it attracted lot of gleeful comments, so gleeful calc.exe uses infinite precision these days to represent rational numbers). In addition many sums are intended to become 0 at the end (the debit and credit should be balanced) so cancellation errors like above actually are quite common. The key issue is that common numbers such as 0.1, 0.2, and so on can't be exactly represented in a double. http://www2.hursley.ibm.com/decimal/ -- Mårten

4 3

[serialization] Base64 padding in basic_text_oprimitive
by Vyacheslav E. Andrejev 10 Jun '08

10 Jun '08

Hello, Code that pads base64 output with '=' looks in basic_text_oprimitive.ipp like following: std::size_t padding = 2 - count % 3; if(padding > 1) *oi = '='; if(padding > 2) *oi = '='; It will give the following transformations of a few simple strings: "012" -> "MDEy=" "0123" -> "MDEyMw" "01234" -> "MDEyMzQ" "012345" -> "MDEyMzQ1=" Which violates the principle of the base 64 that the encoded output length is multiple of 4 bytes. Right output for the samples above should be: "012" -> "MDEy" "0123" -> "MDEyMw==" "01234" -> "MDEyMzQ=" "012345" -> "MDEyMzQ1" The problem with the code above is that the condition (padding > 2) is never satisfied. I think that the proper code should look like std::size_t padding = 2 - count % 3; if (padding < 2) { *oi = '='; if (padding > 0) *oi = '='; } -- -- Vyacheslav Andrejev -- System Architect, Optech International, Inc.

2 3