Mailman 3 April 2005 - Cplusplus-sig

RE: Wrapper for exception translation
by Gottfried.Ganssauge＠HAUFE.DE April 4, 2006

April 4, 2006

> -----Original Message----- > From: David Abrahams [mailto:dave@boost-consulting.com] > Sent: Monday, December 13, 2004 1:04 PM > To: c++-sig(a)python.org; Gottfried Ganßauge > Subject: Re: Wrapper for exception translation > > > Gottfried Ganßauge wrote: > > Hi Dave, > > > > I digged through the class_<> implementation and I think I > know what I > > must do to implement it. Like you suggested I would add another > > argument to the class_base constructor which is used as > another base > > class for the newly created class. > > Hi Gottfried, Hi Dave, > > I don't know if you're still listening, but today I offered to > implement this patch on the C++-sig (see my other post). > Are you still interested? I am still listening but was buried deeply with work so I even had to abandon the work already invested into this. Nonetheless: Yes - I'm still interested. Cheers, Gottfried P.S.: What second Post? I got 2 Copies of this one. > > > > -- > Dave Abrahams > Boost Consulting > http://www.boost-consulting.com >

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Re: exporting __stdcall methods
by David Abrahams Feb. 11, 2006

Feb. 11, 2006

"John Maddock" <john(a)johnmaddock.co.uk> writes: >> Files like boost/type_traits/detail/is_mem_fun_pointer_tester.hpp >> which are outside the Boost.Python library would need to be enhanced >> to deal with __stdcall, etc. > > Should now be fixed in cvs: provided the changes don't break anything else > of course! Fantastic! Thanks, John! -- Dave Abrahams Boost Consulting www.boost-consulting.com

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Pointer to existing Python object
by Andreas Beyer May 20, 2005

May 20, 2005

Hi: I know that there has been some discussion on this subject on c++ sig. However, I could not find a solution for my specific problem and maybe there is no solution. Here we go: I have a container class B that creates instances of class A - both in C++. In Python I can get instances of A from B with a get() method. I would like to get an existing Python object whenever such object existis and I would like to get a new Python object if no Python object for A exists. An example: using namespace boost; class A : public enable_shared_from_this<A> { public: A() : val(0) {}; int val; typedef shared_ptr<A> A_ptr; A_ptr self() { A_ptr self; self = shared_from_this(); return self; } }; class B { public: B() { a = A::A_ptr(new A()); } A::A_ptr a; void set(A::A_ptr a) { this->a = a; } A::A_ptr get() { return a->self(); } }; BOOST_PYTHON_MODULE(ptr_test) { python::class_<A> ("A") .def_readwrite("val", &A::val) ; python::register_ptr_to_python< A::A_ptr >(); python::class_<B>("B") .def("set", &B::set) .def("get", &B::get) ; } In Python I would like to do this: >>> b = B() >>> a1 = b.get() # obtain instance of class A >>> a2 = b.get() # get the *same Python instance* again >>> assert(a1==a2) Traceback (most recent call last): File "<stdin>", line 1, in ? AssertionError >>> The internal representations of instances of A are the same! Whenever I access a C++ member of A I am actually accessing the same object. So I can do this: >>> a1.val = 42 # change internal reference >>> print a2.val 42 >>> However, I cannot do this: >>> a1.foo = 42 >>> print a2.foo Traceback (most recent call last): File "<stdin>", line 1, in ? AttributeError: 'A' object has no attribute 'foo' >>> I think instances of B have to check if there is already an existing Python object. In that case B (or a wrapper of B) should return the existing Python object (i.e. instances of python::object). Is there a way to find such an existing instance? Andreas

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Getting the pointer for a member operator
by Nicodemus May 13, 2005

May 13, 2005

Hello all, Currently Pyste does this: // C++ code struct C { operator const char*() { return "C"; } }; // generated: BOOST_PYTHON_MODULE(_operators) { class_< operators::C >("C", init< >()) .def("__str__", &operators::C::operator const char*) ; } Problem is that this is broken under MSVC.NET 2003. The compiler complains with: """ _operators.cpp(24) : error C2833: 'operator const' is not a recognized operator or type """ ie, the compiler doesn't realize that its the operator const char* that it should get the address to. I tried changing it to: .def("__str__", &operators::C::operator (const char*)) But without success. Does anybody know how I can fix this? Best Regards, Nicodemus.

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Need to understand the following Python Program- Help me..
by jaeho kim April 29, 2005

April 29, 2005

Hi,,, I am very interested about the following Python program, but I am very beginner on Python.. I do not understand this algorithm,, I would appreciated if you give me this algorithm to some other popular programming language. filename="Karp.py" from __future__ import nested_scopes import bisect class _Num: def __init__(self, value, index): self.value = value self.i = index def __lt__(self, other): return self.value < other.value # This implements the Karmarkar-Karp heuristic for partitioning a set # in two, i.e. into two disjoint subsets s.t. their sums are # approximately equal. It produces only one result, in O(N*log N) # time. A remarkable property is that it loves large sets: in # general, the more numbers you feed it, the better it does. class Partition: def __init__(self, nums): self.nums = nums sorted = [_Num(nums[i], i) for i in range(len(nums))] sorted.sort() self.sorted = sorted def run(self): sorted = self.sorted[:] N = len(sorted) connections = [[] for i in range(N)] while len(sorted) > 1: bigger = sorted.pop() smaller = sorted.pop() # Force these into different sets, by "drawing a # line" connecting them. i, j = bigger.i, smaller.i connections[i].append(j) connections[j].append(i) diff = bigger.value - smaller.value assert diff >= 0 bisect.insort(sorted, _Num(diff, i)) # Now sorted contains only 1 element x, and x.value is # the difference between the subsets' sums. # Theorem: The connections matrix represents a spanning tree # on the set of index nodes, and any tree can be 2-colored. # 2-color this one (with "colors" 0 and 1). index2color = [None] * N def color(i, c): if index2color[i] is not None: assert index2color[i] == c return index2color[i] = c for j in connections[i]: color(j, 1-c) color(0, 0) # Partition the indices by their colors. subsets = [[], []] for i in range(N): subsets[index2color[i]].append(i) return subsets N = 50 import math x = [math.sqrt(i) for i in range(1, N+1)] p = Partition(x) s, t = p.run() sum1 = 0L sum2 = 0L for i in s: sum1 += x[i] for i in t: sum2 += x[i] print "Set 1 sum", repr(sum1) print "Set 2 sum", repr(sum2) print "difference", repr(abs(sum1 - sum2)) Thanks for you help... Larry Jaeho Kim Larry Jaeho Kim __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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RE: [C++-sig] Need to understand the following Python Program- He lp me..
by Max Khesin April 29, 2005

April 29, 2005

Wrong forum - this one is dedicated to Python/C++ binding. Please try comp.lang.python on Usenet, or better yet google "karp algorithm" - I am sure you will find many implementations. max -----Original Message----- From: jaeho kim [mailto:jaehokim1@yahoo.com] Sent: Friday, April 29, 2005 11:19 AM To: c++-sig(a)python.org Subject: [C++-sig] Need to understand the following Python Program- Help me.. Hi,,, I am very interested about the following Python program, but I am very beginner on Python.. I do not understand this algorithm,, I would appreciated if you give me this algorithm to some other popular programming language. filename="Karp.py" from __future__ import nested_scopes import bisect class _Num: def __init__(self, value, index): self.value = value self.i = index def __lt__(self, other): return self.value < other.value # This implements the Karmarkar-Karp heuristic for partitioning a set # in two, i.e. into two disjoint subsets s.t. their sums are # approximately equal. It produces only one result, in O(N*log N) # time. A remarkable property is that it loves large sets: in # general, the more numbers you feed it, the better it does. class Partition: def __init__(self, nums): self.nums = nums sorted = [_Num(nums[i], i) for i in range(len(nums))] sorted.sort() self.sorted = sorted def run(self): sorted = self.sorted[:] N = len(sorted) connections = [[] for i in range(N)] while len(sorted) > 1: bigger = sorted.pop() smaller = sorted.pop() # Force these into different sets, by "drawing a # line" connecting them. i, j = bigger.i, smaller.i connections[i].append(j) connections[j].append(i) diff = bigger.value - smaller.value assert diff >= 0 bisect.insort(sorted, _Num(diff, i)) # Now sorted contains only 1 element x, and x.value is # the difference between the subsets' sums. # Theorem: The connections matrix represents a spanning tree # on the set of index nodes, and any tree can be 2-colored. # 2-color this one (with "colors" 0 and 1). index2color = [None] * N def color(i, c): if index2color[i] is not None: assert index2color[i] == c return index2color[i] = c for j in connections[i]: color(j, 1-c) color(0, 0) # Partition the indices by their colors. subsets = [[], []] for i in range(N): subsets[index2color[i]].append(i) return subsets N = 50 import math x = [math.sqrt(i) for i in range(1, N+1)] p = Partition(x) s, t = p.run() sum1 = 0L sum2 = 0L for i in s: sum1 += x[i] for i in t: sum2 += x[i] print "Set 1 sum", repr(sum1) print "Set 2 sum", repr(sum2) print "difference", repr(abs(sum1 - sum2)) Thanks for you help... Larry Jaeho Kim Larry Jaeho Kim __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ C++-sig mailing list C++-sig(a)python.org http://mail.python.org/mailman/listinfo/c++-sig This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.

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virtual overrides and custom smart pointers
by Leonard "paniq" Ritter April 29, 2005

April 29, 2005

hi, i'm running into a problem i'm trying to fix since several days without much luck. it seems my custom smart pointer class becomes worthless when wrapper<> is used to construct an object whose methods can be overridden in python. wrapper export code: class_<WindowEventsWrap, bases<Mu::Interface::Unknown>, Ptr<WindowEventsWrap>, boost::noncopyable>("WindowEvents") .def("OnWidgetEvent",pure_virtual(&WindowEvents::OnWidgetEvent)) .def("WidgetEventHandled",pure_virtual(&WindowEvents::WidgetEventHandled)) ; wrapper declaration: struct WindowEventsWrap : InterfaceImplementation<WindowEventsWrap, Implements<Mu::Sandoz::Interface::WindowEvents> >, wrapper< Mu::Sandoz::Interface::WindowEvents > python test code: class MyWindowEvents(Sandoz.WindowEvents): def OnWidgetEvent(self, event): print event.type return Sandoz.Result.NotImplemented def WidgetEventHandled(self, event, widget): print event.type, widget return Sandoz.Result.NotImplemented def Main(): mwe = MyWindowEvents() view = Sandoz.ViewFrame("µ.Sandoz.ViewFrame") view.Connect(mwe) del mwe connect adds a reference to the mwe callback object and view calls that object later on. this is known to work. however when i delete mwe right after Connect(), the object itself persists, but its overridden methods (and i guess the underlying python object as well) are gone. no Release or AddReference on my object is called from wrapper_base, so i assume it is not using my custom smart pointer class which deals with this stuff. can someone suggest a solution to this problem? best regards, leonard

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for python library file
by jianbing wu April 29, 2005

April 29, 2005

Hi guys, I am currently write a C++ program which will use the "python24.lib", but when I compiled my program under the debug version, the .Net compiler complains not finding "pythod24_d.lib" (as I knew this library file is only used for debugging purpose). But I cannot find it in the python installation folder. Would someone please give me this file or tell me how to create this file? Thank you, Ivory __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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RE: [C++-sig] Re: Newbie ... trouble compiling Boost.Python
by Cain, Ben (Contractor-Summit) April 29, 2005

April 29, 2005

David, Thank you for your patience with a Python newbie. I hope to contribute to this mailing list as I come up to speed. Many Thanks, Ben David Abrahams wrote: > > In that case you need to use -sTOOLS=mingw. > http://www.boost.org/more/getting_started.html#Tools shows that > -sTOOLS=gcc is reserved for Unix and Cygwin. .org/mailman/listinfo/c++-sig [Ben Cain wrote:]

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Visual C++ 2005
by Neil Hodgson April 28, 2005

April 28, 2005

Does anyone know if compilation of Boost.Python based code works better with Visual C++ 2005 compared to the 2003 version? Visual C++ 2003 is OK but requires breaking wrappers up into multiple files and compilation can be very slow and memory-intensive. How can Boost.Jam be instructed to look for Visual C++ 2005? Both versions of the compiler are installed here and Boost.Jam always finds 2003. A beta of the express edition of Visual C++ 2005 is a free download, IIRC about 60 Megs. Neil

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