Mailman 3 November 2005 - Cplusplus-sig

Limits of implicitly_convertible?
by Hans Meine Nov. 18, 2005

Nov. 18, 2005

Hi! I could not get implicitly_convertible<list, MyVector>() to work *at all*, so I tried the example from the documentation. (BTW: My compiler told me that operator int() had to be const, that should probably be fixed in the docs.) That simple example worked, but when I changed the constructor to take a list instead of an int, it ceased working. Attached you'll find a minimal testcase. -- Ciao, / / .o. /--/ ..o / / ANS ooo

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(no subject)
by Petya Vasileva Nov. 18, 2005

Nov. 18, 2005

hey, i am trying to run this program, but it's not letting me. Would you help me, please! Thank you!!! //This program reads in a customer's name and time * //they were in a parking garage. It then calculates* //and prints out the average payment of all the * //people, the payment each person owes, and the * //change each person gets back. It also calculates* //and prints out anyone that is under the average * //payment. * //************************************************** # include <iostream> # include <fstream> # include <iomanip> using namespace std; //**************************************************** // Stubs or prototypes of functions double AveragePayment(); void Initialize(int & iNumCustomers, int & iNumUnderAverage); void Titles(ofstream & OutputFile); void ReadName(ifstream& InputFile, char strNm[]); int ReadMinutes(ifstream & InputFile); int Payment(int iMinutes); void ChangeDue (int iPayment, int & iNumQuarters, int & iNumDimes, int & iNumNickels, int & iNumPennies); void PrintIt (ofstream & OutputFile, char strNm[], int iNumMin, intiPayment, int iNumQuarters, int iNumDimes, int iNumNickels, int iNumPennies); void UnderAverage(int iPayment, double dAveragePayment, int &iNumCustomers, int & iNumUnderAverage, ofstream &ofPaymentFile); void PrintAverage(double dAveragePayment, int iNumCustomers, intiNumUnderAverage, ofstream &OutputFile); void FreezeScreen(); //**************************************************** void main() { char strNm[20];//Customer name int iNumMin; //Number of minutes the customer was in the garage int iNumQuarters; int iNumDimes; int iNumNickels; int iNumPennies; int iNumCustomers; int iNumUnderAverage; //int iNumUnderAverage; double dAveragePayment; //Average amount paid for parking int iPayment; //Payment due double iChangeDue; //Change due to the customer double dPercentCust; //Percent of customers under the average ifstream InputFile; //Input file name ofstream OutputFile; //Output file name AveragePayment(); InputFile.open("ASS9.txt"); Initialize (iNumCustomers, iNumUnderAverage); if (! InputFile) { cout << "Error in opening file" << endl; cout << endl; FreezeScreen(); return; } OutputFile.open("Output.txt"); Titles(OutputFile); while(! InputFile.eof()) { ReadName(InputFile, strNm); ReadMinutes(InputFile); Payment(iNumMin); ChangeDue (iPayment, iNumQuarters, iNumDimes, iNumNickels, iNumPennies); PrintIt (OutputFile, strNm, iNumMin, iPayment, iNumQuarters, iNumDimes, iNumNickels, iNumPennies); UnderAverage(iPayment, dAveragePayment, iNumCustomers, iNumUnderAverage, OutputFile); PrintAverage(dAveragePayment, iNumCustomers, iNumUnderAverage, OutputFile); } InputFile.close(); OutputFile.close(); FreezeScreen(); } //**************************************************** //This function freezes the screen and stops the program. void FreezeScreen() { fflush(stdin); cout << "Hit enter to continue"; getchar(); } //**************************************************** //This function returns the average amount paid by customers //to park in the garage. double AveragePayment() { ifstream InputFile; char strNm[20]; int iNumCustomers; int iNumMin; int iPayment; double dAveragePayment; InputFile.open("ASS9.txt"); if (InputFile.fail()) { cout << "Error Opening Input File" << endl; FreezeScreen(); return -1; } else { while (! InputFile.eof()) { InputFile.getline(strNm, 20); Payment(iNumMin); iNumCustomers++; } } InputFile.close(); dAveragePayment = iPayment / iNumCustomers; return dAveragePayment; } //**************************************************** //This function initializes all the variables void Initialize(int & iNumCustomers, int & iNumUnderAverage) { int iCntr = 0; int iNumMin = 0; //Number of minutes the customer was in the garage int iNumQuarters = 0; int iNumDimes = 0; int iNumNickels = 0; int iNumPennies = 0; double dAveragePayment = 0; //Average amount paid for parking double dPayment = 0; //Payment due int iChangeDue = 0; //Change due to the customer double dPercentCust = 0; //int iNumCustomers = 0; //int iNumUnderAverage = 0; //return iNumCustomers, iNumUnderAverage; } //**************************************************** //This function prints a title for the table in the output file. void Titles(ofstream & OutputFile) { OutputFile << setw(30) << "Parking Garage Payment" << endl; } //**************************************************** //This function reads in the name of the customer from the input file void ReadName(ifstream & InputFile, char strNm[20]) { InputFile.getline(strNm, 20); } //**************************************************** //This function reads in the number of minutes the customer was in the //garage. int ReadMinutes(ifstream & InputFile) { int iNumMin; InputFile >> iNumMin; return iNumMin; } //**************************************************** int Payment(int iNumMin) { int iPayment; if(iNumMin <= 60) { iPayment = 50; } else { iPayment = (iNumMin - 60)* 1; } if(iPayment >= 1000) { iPayment = 1000; } return iPayment; } //**************************************************** void ChangeDue (int iPayment, int & iNumQuarters, int & iNumDimes, int & iNumNickels, int & iNumPennies) { int iChangeDue; iChangeDue = 1000 - iPayment; iNumQuarters = iChangeDue % 25; iNumDimes = iNumQuarters % 10; iNumNickels = iNumDimes % 5; iNumPennies = iNumNickels % 1; //return iChangeDue, iNumQuarters, iNumDimes, iNumNickels, iNumPennies; } //**************************************************** void PrintIt (ofstream & OutputFile, char strNm[], int iNumMin, intiPayment, int iNumQuarters, int iNumDimes, int iNumNickels, int iNumPennies) { OutputFile << setw(7) << strNm << setw(15)<< iNumMin << setw(21)<< iPayment << setw(20)<< iNumQuarters << setw(20)<< iNumDimes << setw(21)<< iNumNickels << setw(20)<< iNumPennies << endl; } //**************************************************** void UnderAverage(int iPayment, double dAveragePayment, int &iNumCustomers, int & iNumUnderAverage, ofstream &OutputFile) { double dPercentCust; while (iPayment < dAveragePayment) { OutputFile << "Under Average"; iNumUnderAverage ++; } dPercentCust = iNumUnderAverage/iNumCustomers; //return iNumUnderAverage, iNumCustomers, dPercentCust; } //*************************************************** void PrintAverage(double dAveragePayment, int iNumCustomers, intiNumUnderAverage, ofstream &OutputFile) { double dAveAmtPaid; double dPercentCust; OutputFile << "The average payment was: " << dAveAmtPaid << "." << endl; OutputFile << "The percent of customers that are under the average is: " << dPercentCust << "." << endl; } //***************************************************

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Raw constructor (i.e. combination of make_constructor and raw_function)
by Hans Meine Nov. 17, 2005

Nov. 17, 2005

Hi! I guess I am not the first one trying to do this, but the closest discussion I could find did not solve this topic: http://mail.python.org/pipermail/c++-sig/2005-June/008959.html I am trying to do something like python::class_<MyVector>("PythonVector", python::no_init) .def("__init__", python::raw_function(&createVector, 1)); But this gives the vector as first element of the args tuple to createVector(). Now, my createVector looks like this: MyVector createVector(const python::tuple &args, const python::dict &) { int size = python::len(args); MyVector result(size); for(int i=0; i<size; ++i) result[i] = python::extract<double>(args[i])(); return result; } Is there a way to combine the functionality of raw_function and make_constructor? (I even tried staticmethod("__init__") ;-) ) -- Ciao, / / .o. /--/ ..o / / ANS ooo

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Something like boost::any ... custom conversions?
by Alex Mohr Nov. 17, 2005

Nov. 17, 2005

Suppose I have a type that is much like boost::any. If I have an instance of this in python (say holding an int), then I want to be able to call wrapped c++ code which takes arguments of held types (say foo(int)) by passing my any-like object directly. That is, I want my any-like object to try to convert to the desired c++ type by checking to see if it's holding the desired c++ type. Can anyone point me in a general direction of where to look to do this sort of thing? I've tried looking at the conversion information in the reference manual, and I've looked at container_conversions.h, but I have to admit that things are still muddy for me. The lvalue_from_pytype stuff seems like it might be in the right direction, but I don't really want lvalue conversion. I only care about passing these things as rvalues. Thanks a lot, Alex

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Python help() not showing imported Boost.Python-wrapped classes
by Doug Gregor Nov. 16, 2005

Nov. 16, 2005

Python's interactive help is not showing classes exported using Boost.Python. For instance, I have a module "_support" that uses Boost.Python like this: BOOST_PYTHON_MODULE(_support) { using boost::python::class_; using boost::python::enum_; using boost::python::init; class_<point2d>("Point2D"); class_<point3d>("Point3D"); enum_<default_color_type>("Color"); def("distance", &point_2d_distance); } Now, that gets pulled into a package "bgl" that has this in its __init__.py: from _support import * If I run help(bgl), something odd happens. Under the CLASSES heading, the "Color" enum gets documented but Point2D and Point3D do not. Under the FUNCTIONS heading, "distance" gets documented. \ If I run help(bgl._support), I get Point2D and Point3D documented (in the CLASSES section, of course) but neither "Color" nor "distance". Ideally, the _support module would be invisible to the user, and all of these classes and functions would show up when one uses help(bgl). Is this possible? Cheers, Doug

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[Boost.Python] Solaris / gcc2.95.2 wchar.h problems
by Jan Langer Nov. 16, 2005

Nov. 16, 2005

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello, I read that this newsgroup is suitable for Boost.Python problems. I wanted to compile Boost 1.33.0 and I ran into problems with Boost.Python. My system is Solaris 5.7 with gcc 2.95.2. The Python version is 2.4.1. When compling the file inheritance.cpp it includes integer_traits.hpp which exits with an error in line 116 because WCHAR_MIN and WCHAR_MAX are not defined. However, my wchar.h include file defines those two macros. I couldn't find what was going wrong, but moving the include of integer_traits.hpp in inheritance.cpp to the top of the list of include files solves the problem. But this results in the warning below. - ----- gcc-C++-action ../../../bin/boost/libs/python/build/libboost_python.a/gcc/debug/inheritance.o In file included from /data/tmp/laja/boost_1_33_0/boost/python/detail/wrap_python.hpp:30, from /data/tmp/laja/boost_1_33_0/boost/python/detail/prefix.hpp:13, from /data/tmp/laja/boost_1_33_0/boost/python/type_id.hpp:8, from /data/tmp/laja/boost_1_33_0/boost/python/object/inheritance.hpp:8, from /data/tmp/laja/boost_1_33_0/libs/python/build/../src/object/inheritance.cpp:6: /home/4all/packages/python/2.4.1/include/python2.4/pyconfig.h:820: warning: `_FILE_OFFSET_BITS' redefined /usr/include/sys/feature_tests.h:96: warning: this is the location of the previous definition - ------ If someone is interested in this problem, I could provide more details. Jan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.6 (SunOS) Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFDecT4yJOS3PG4wcwRAnRIAJ9LFKa6LWrmlDVrWL7GOu0po9bC9QCgoGG0 fWim8v7NG4Eg7uhoIVcyct4= =OC/Y -----END PGP SIGNATURE-----

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Specific exception classes
by Emmanuel Taurel Nov. 16, 2005

Nov. 16, 2005

Hello everybody. I am using BPL to wrap a C++ library and I would like to define my own exception. Therefore, I have written one exception translator that I have registered with the "register_exception_translator". My exception translator looks like this (DevFailed is the name of the C++ exception class) void translator_dev_failed(const DevFailed &the_ex) { PyObject *py_exc = PyErr_NewException("PyTangoDs.DevFailed",NULL,NULL); PyErr_SetString(py_exc,the_ex.errors[0].desc.in()); } In Python, I have: from PyTangoDs import * try: ... except DevFailed,e: print 'Received a DevFailed exception:',e except: print 'An unforeseen exception occured....' The python interpreter complains that it does not know the DevFailed name with this error : Traceback (most recent call last): File "main.py", line 19, in ? except DevFailed,e: NameError: name 'DevFailed' is not defined My question is : How is it possible to have your own exception ? Thank's for your answer Sincerely Emmanuel Taurel (etaurel(a)cells.es)

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pyste generation of getitem/setitem .def's
by Grant Goodyear Nov. 15, 2005

Nov. 15, 2005

I recently hacked up my boost.python interface file to add __getitem__ and __setitem__ methods: class_< EMAN::EMData >("EMData", init< >()) .def(init< const EMAN::EMData& >()) .def("__getitem__", &emdata_getitem) .def("__setitem__", &emdata_setitem) I was generating the interface file using pyste, Include("emdata_wrapitems.h") # *item wrappers declared here EMData = Class("EMAN::EMData", "emdata.h") but I'm not sure how to get pyste to add the getitem/setitem .def's for me. I'm sure there's a simple trick that's more elegant than sedding the file, but I'm not sure what it is. There's "declaration_code" and "module_code"; is there a "class_code" or something similar? Thanks, Grant -- Grant Goodyear web: http://www.grantgoodyear.org e-mail: grant(a)grantgoodyear.org

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swig?
by Neal Becker Nov. 10, 2005

Nov. 10, 2005

I noticed that recent versions of swig have quite significantly advanced the support for c++. I wonder if anyone has experience they can share, regarding a comparison of boost::python with a recent swig. I have been using boost::python for some time, but am interested in considering swig, because in my present environment, it would be easier for me to deploy code using swig.

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enum strangeness...
by Alex Mohr Nov. 10, 2005

Nov. 10, 2005

I noticed something today about enums that I've wrapped with boost.python. Here's a small example. #include <boost/python.hpp> using namespace boost::python; struct Foo { enum Bar { Baz }; }; BOOST_PYTHON_MODULE(Mod) { scope fooScope = class_<Foo>("Foo"); enum_<Foo::Bar>("Bar") .value("Baz", Foo::Baz) .export_values(); } Now, in Python I can refer to the enum values by saying 'Mod.Foo.Baz' which is what I expect, but it seems to recur in a strange way. I can also say: Mod.Foo.Baz.Baz.Baz.Baz.Baz.Baz.Baz.Baz for as long as I like. This seems relatively benign, but strange. Is it expected? Thanks, Alex

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