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• [C++] Write connected components of a graph using Boost Graph

  - by conradlee

  I have an file that is a long list of weighted edges, in the following form node1_id node2_id weight node1_id node3_id weight and so on. So one weighted edge per line. I want to load this file into boost graph and find the connected components in the graph. Each of these connected components is a subgraph. For each of these component subgraphs, I want to write the edges in the above-described format. I want to do all this using boost graph. This problem is in principle simple, it's just I'm not sure how to implement it neatly because I don't know my way around Boost Graph. I have already spent some hours and have code that will find the connected components, but my version is surely much longer and more complicated that necessary---I'm hoping there's a boost-graph ninja out there that can show me the right, easy way.

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• Mocking using boost::shared_ptr and AMOP

  - by Edison Gustavo Muenz

  Hi, I'm trying to write mocks using amop. I'm using Visual Studio 2008. I have this interface class: struct Interface { virtual void Activate() = 0; }; and this other class which receives pointers to this Interface, like this: struct UserOfInterface { void execute(Interface* iface) { iface->Activate(); } }; So I try to write some testing code like this: amop::TMockObject<Interface> mock; mock.Method(&Interface::Activate).Count(1); UserOfInterface user; user.execute((Interface*)mock); mock.Verifiy(); It works! So far so good, but what I really want is a boost::shared_ptr in the execute() method, so I write this: struct UserOfInterface { void execute(boost::shared_ptr<Interface> iface) { iface->Activate(); } }; How should the test code be now? I tried some things, like: amop::TMockObject<Interface> mock; mock.Method(&Interface::Activate).Count(1); UserOfInterface user; boost::shared_ptr<Interface> mockAsPtr((Interface*)mock); user.execute(mockAsPtr); mock.Verifiy(); It compiles, but obviously crashes, since at the end of the scope the variable 'mock' gets double destroyed (because of the stack variable 'mock' and the shared_ptr). I also tried to create the 'mock' variable on the heap: amop::TMockObject<Interface>* mock(new amop::TMockObject<Interface>); mock->Method(&Interface::Activate).Count(1); UserOfInterface user; boost::shared_ptr<Interface> mockAsPtr((Interface*)*mock); user.execute(mockAsPtr); mock->Verifiy(); But it doesn't work, somehow it enters an infinite loop, before I had a problem with boost not finding the destructor for the mocked object when the shared_ptr tried to delete the object. Has anyone used amop with boost::shared_ptr successfully?

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• Eclipse c++ with mingw comiler cant build boost regex example, can find .a library files

  - by Kim

  Hi, I'm trying to build the boost regex example in eclipse using mingw on vista. I built boost ok with mingw as there are library files XXXX.a. I could build/compile the first boost example that doesnt require any of the compiled boost libraries. When I compile the regex example I get a linker error saying it cant find the library file. I have tried various libray file names eg leave off the .a extension, leave off the lib prefix etc. Now the interesting thing is that if I leave off the library extension and rename the library file to XXX.lib it works and runs ok. So why cant it read the .a library file? It must be my setup somewhere but I dont know where or what to set. From what I read everyone is ok linking the .a file except me :( Thanks in advance, Kim

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• Python - CSV: Large file with rows of different lengths

  - by dassouki

  In short, I have a 20,000,000 line csv file that has different row lengths. This is due to archaic data loggers and proprietary formats. We get the end result as a csv file in the following format. MY goal is to insert this file into a postgres database. How Can I do the following: Keep the first 8 columns and my last 2 columns, to have a consistent CSV file Add a Column to the file. 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0, img_id.jpg, -50 1, 2, 3, 4, 5, 0,0,0,0,0,0,0,0,0,0,0 img_id.jpg, -50

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• How do I install python gtkmozembed package or is there a replacement of python GtkMozEmbed in windo

  - by user198729

  self.widget = gtkmozembed.MozEmbed() self.widget.set_size_request(x + 18, y) I can't find a binary installer of gtkmozembed, is there an equivalent that can do the above ?

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• boost::serialization of mutual pointers

  - by KneLL

  First, please take a look at these code: class Key; class Door; class Key { public: int id; Door *pDoor; Key() : id(0), pDoor(NULL) {} private: friend class boost::serialization::access; template <typename A> void serialize(A &ar, const unsigned int ver) { ar & BOOST_SERIALIZATION_NVP(id) & BOOST_SERIALIZATION_NVP(pDoor); } }; class Door { public: int id; Key *pKey; Door() : id(0), pKey(NULL) {} private: friend class boost::serialization::access; template <typename A> void serialize(A &ar, const unsigned int ver) { ar & BOOST_SERIALIZATION_NVP(id) & BOOST_SERIALIZATION_NVP(pKey); } }; BOOST_CLASS_TRACKING(Key, track_selectively); BOOST_CLASS_TRACKING(Door, track_selectively); int main() { Key k1, k_in; Door d1, d_in; k1.id = 1; d1.id = 2; k1.pDoor = &d1; d1.pKey = &k1; // Save data { wofstream f1("test.xml"); boost::archive::xml_woarchive ar1(f1); // !!!!! (1) const Key *pK = &k1; const Door *pD = &d1; ar1 << BOOST_SERIALIZATION_NVP(pK) << BOOST_SERIALIZATION_NVP(pD); } // Load data { wifstream i1("test.xml"); boost::archive::xml_wiarchive ar1(i1); // !!!!! (2) A *pK = &k_in; B *pD = &d_in; // (2.1) //ar1 >> BOOST_SERIALIZATION_NVP(k_in) >> BOOST_SERIALIZATION_NVP(d_in); // (2.2) ar1 >> BOOST_SERIALIZATION_NVP(pK) >> BOOST_SERIALIZATION_NVP(pD); } } The first (1) is a simple question - is it possible to pass objects to archive without pointers? If simply pass objects 'as is' that boost throws exception about duplicated pointers. But I'm confused of creating pointers to save objects. The second (2) is a real trouble. If comment out string after (2.1) then boost will corectly load a first Key object (and init internal Door pointer pDoor), but will not init a second Door (d_in) object. After this I have an inited *k_in* object with valid pointer to Door and empty *d_in* object. If use string (2.2) then boost will create two Key and Door objects somewhere in memory and save addresses in pointers. But I want to have two objects *k_in* and *d_in*. So, if I copy a values of memory objects to local variables then I store only addresses, for example, I can write code after (2.2): d_in.id = pD->id; d_in.pKey = pD->pKey; But in this case I store only a pointer and memory object remains in memory and I cannot delete it, because *d_in.pKey* will be unvalid. And I cannot perform a deep copy with operator=(), because if I write code like this: Key &operator==(const Key &k) { if (this != &k) { id = k.id; // call to Door::operator=() that calls *pKey = *d.pKey and so on *pDoor = *k.pDoor; } return *this; } then I will get a something like recursion of operator=()s of Key and Door. How to implement proper serialization of such pointers?

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• Using httplib2 in python 3 properly? (Timeout problems)

  - by Sho Minamimoto

  Hey, first time post, I'm really stuck on httplib2. I've been reading up on it from diveintopython3.org, but it mentions nothing about a timeout function. I look up the documentation, but the only thing I see is an ability to put a timeout int but there are no units specified (seconds? milliseconds? What's the default if None?) This is what I have (I also have code to check what the response is and try again, but it's never tried more than once) h = httplib2.Http('.cache', timeout=None) for url in list: response, content = h.request(url) more stuff... So the Http object stays around until some arbitrary time, but I'm downloading a ton of pages from the same server, and after a while, it hangs on getting a page. No errors are thrown, the thing just hangs at a page. So then I try: h = httplib2.Http('.cache', timeout=None) for url in list: try: response, content = h.request(url) except: h = httplib2.Http('.cache', timeout=None) more stuff... But then it recreates another Http object every time (goes down the 'except' path)...I dont understand how to keep getting with the same object, until it expires and I make another. Also, is there a way to set a timeout on an individual request? Thanks for the help!

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• Generating permutation in Python with specific rule

  - by twfx

  Let say a=[A, B, C, D], each element has a weight w, and is set to 1 if selected, 0 if otherwise. I'd like to generate permutation in the below order 1,1,1,1 1,1,1,0 1,1,0,1 1,1,0,0 1,0,1,1 1,0,1,0 1,0,0,1 1,0,0,0 Let's w=[1,2,3,4] for item A,B,C,D ... and max_weight = 4. For each permutation, if the accum weight has exceeded max_weight, stop calculation for that permutation, move to next permutation. For eg. 1,1,1 --> 6 > 4, exceeded, stop, move to next 1,1,1 --> 6 > 4, exceeded, stop, move to next 1,1,0,1 --> 7 > 4 finished, move to next 1,1,0,0 --> 3 finished, move to next 1,0,1,1 --> 8 > 4, finished, stop, move to next 1,0,1,0 --> 4 finished, move to next 1,0,0,1 --> 5 > 4 finished, move to next 1,0,0,0 --> 1 finished, move to next [1,0,1,0] is the best combination which does not exceeded max_weight 4 My questions are What's the algorithm which generate the required permutation? Or any suggestion I could generate the permutation? As the number of element can be up to 10000, and the calculation stop if the accum weight for the branch exceeds max_weight, it is not necessary to generate all permutation first before the calculation. How can the algo in (1) generate permutation on the fly?

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• How is the 'is' keyword implemented in Python?

  - by Srikanth

  ... the is keyword that can be used for equality in strings. >>> s = 'str' >>> s is 'str' True >>> s is 'st' False I tried both __is__() and __eq__() but they didn't work. >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __is__(self, s): ... return self.s == s ... >>> >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work False >>> >>> class MyString: ... def __init__(self): ... self.s = 'string' ... def __eq__(self, s): ... return self.s == s ... >>> >>> m = MyString() >>> m is 'ss' False >>> m is 'string' # <--- Expected to work, but again failed False >>> Thanks for your help!

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• How to build sqlite for Python 2.4?

  - by Verrtex

  I would like to use pysqlite interface between Python and sdlite database. I have already Python and SQLite on my computer. But I have troubles with installation of pysqlite. During the installation I get the following error message: error: command 'gcc' failed with exit status 1 As far as I understood the problems appears because version of my Python is 2.4.3 and SQLite is integrated in Python since 2.5. However, I also found out that it IS possible to build sqlite for Python 2.4 (using some tricks, probably). Does anybody know how to build sqlite for Python 2.4? As another option I could try to install higher version of Python. However I do not have root privileges. Does anybody know what will be the easiest way to solve the problem (build SQLite fro Python 2.4, or install newer version of Python)? I have to mention that I would not like to overwrite the old version version of Python. Thank you in advance.

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• Checking for module availability programmatically in Python?

  - by user248237

  given a list of module names (e.g. mymods = ['numpy', 'scipy', ...]) how can I check if the modules are available? I tried the following but it's incorrect: for module_name in mymods: try: import module_name except ImportError: print "Module %s not found." %(module_name) thanks.

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• Python try...except comma vs 'as' in except

  - by peter

  What is the difference between ',' and 'as' in except statements, eg: try: pass except Exception, exception: pass and: try: pass except Exception as exception: pass Is the second syntax legal in 2.6? It works in CPython 2.6 on Windows but the 2.5 interpreter in cygwin complains that it is invalid. If they are both valid in 2.6 which should I use?

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• Boost singleton and restricted

  - by Ockonal

  Hello, I'm using boost singleton from thread/detail. There is in manual, that constructor should have signlature: boost::restricted. But I can't find any reference for this type in boost library. Why do I need in this and where I can find it?

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• importing files in python

  - by Yosy

  I have that file structure- Blog\DataObjects\User.py Blog\index.py I want to import the function(say_hello) at User.py from index.py. I am trying this code - from Blog.DataObjects.User import say_hello say_hello() And I have that error - Traceback (most recent call last): File "index.py", line 1, in <module> from Blog.DataObjects import User ImportError: No module named Blog.DataObjects

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• python __getattr__ help

  - by Stefanos Tux Zacharakis

  Reading a Book, i came across this code... # module person.py class Person: def __init__(self, name, job=None, pay=0): self.name = name self.job = job self.pay = pay def lastName(self): return self.name.split()[-1] def giveRaise(self, percent): self.pay = int(self.pay *(1 + percent)) def __str__(self): return "[Person: %s, %s]" % (self.name,self.pay) class Manager(): def __init__(self, name, pay): self.person = Person(name, "mgr", pay) def giveRaise(self, percent, bonus=.10): self.person.giveRaise(percent + bonus) def __getattr__(self, attr): return getattr(self.person, attr) def __str__(self): return str(self.person) It does what I want it to do, but i do not understand the __getattr__ function in the Manager class. I know that it Delegates all other attributes from Person class. but I do not understand the way it works. for example why from Person class? as I do not explicitly tell it to. person(module is different than Person(class) Any help is highly appreciated :)

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• boost::bind breaks strict-aliasing rules?

  - by Kyle

  Using Boost 1.43 and GCC 4.4.3, the following code boost::bind(&SomeObject::memberFunc, this, _1)); Generates the following warning boost/function/function_base.hpp:321: warning: dereferencing type-punned pointer will break strict-aliasing rules What's the correct way to eliminate these warnings without setting -fno-strict-aliasing?

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• Python with PIL and Libjpeg on Leopard

  - by thescreamingdrills

  I'm having trouble getting pictures supported with PIL - it throws me this: "IOError: decoder jpeg not available" I installed PIL from binary, not realizing I needed libjpeg. I installed libjpeg and freetype2 through fink. I tried to reinstall PIL using instructions from http://timhatch.com/ (bottom of the page) "* Download PIL 1.1.6 source package and have the Developer Tools already installed * Patch setup.py with this patch so it can find the Freetype you already have. (patch -p0 < leopard_freetype2.diff) * sudo apt-get install libjpeg if you have fink (otherwise, build by hand and adjust paths)" But I'm still getting the same error. I'm on Leopard PPC.

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• Uncompressing zlib data using boost::iostreams::filtering_streambuf trouble

  - by GuitaringEgg

  I'm trying to write a small class that will load the chunk data from part of a minecraft world file. I'm to the point where I have stored some data in a char array which was compressed with zlib and need to decompress it. I'm trying to use the boost filtering_streambuf to do this. char * rawChunk = new char[length - 1]; // Load chunk data stringstream ssRawChunk(rawChunk); boost::iostreams::filtering_istream in; in.push(boost::iostreams::zlib_decompressor()); in.push(ssRawChunk); stringstream ssOut; boost::iostreams::copy(in, ssOut); My problem is that rawChunk contains null data, so when coping data from (char*) rawChunk to (stringstream) ssRawChunk, it terminates at ~257 instead of the expected length 2154. Is there any way to use filtering_streambuf without stringstream to allow for null data or is there a way to stop stringstream to not terminate on null data?

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• Gamma Distribution in Boost

  - by Kamchatka

  Hello, I'm trying to use the Gamma distribution from boost::math but it looks like it isn't possible to use it with boost::variate_generator. Could someone confirm that? Or is there a way to use it. I discovered that there is a boost::gamma_distribution undocumented that could probably be used too but it only allows to choose the alpha parameter from the distribution and not the beta. Thanks!

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• How to send large objects using boost::asio

  - by Max

  Good day. I'm receiving a large objects via the net using boost::asio. And I have a code: for (int i = 1; i <= num_packets; i++) boost::asio::async_read(socket_, boost::asio::buffer(Obj + packet_size * (i - 1), packet_size), boost::bind(...)); Where My_Class * Obj. I'm in doubt if that approach possible (because i have a pointer to an object here)? Or how it would be better to receive this object using packets of fixed size in bytes? Thanks in advance.

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• Boost causes an invalid block while overloading new/delete operators

  - by user555746

  Hi, I have a problem which appears to a be an invalid memory block that happens during a Boost call to Boost:runtime:cla::parser::~parser. When that global delete is called on that object, C++ asserts on the memory block as an invalid: dbgdel.cpp(52): /* verify block type */ _ASSERTE(_BLOCK_TYPE_IS_VALID(pHead->nBlockUse)); An investigation I did revealed that the problem happened because of a global overloading of the new/delete operators. Those overloadings are placed in a separate DLL. I discovered that the problem happens only when that DLL is compiled in RELEASE while the main application is compiled in DEBUG. So I thought that the Release/Debug build flavors might have created a problem like this in Boost/CRT when overloading new/delete operators. So I then tried to explicitly call to _malloc_dbg and _free_dbg withing the overloading functions even in release mode, but it didn't solve the invalid heap block problem. Any idea what the root cause of the problem is? is that situation solvable? I should stress that the problem began only when I started to use Boost. Before that CRT never complained about any invalid memory block. So could it be an internal Boost bug? Thanks!

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• Naming a typedef for a boost::shared_ptr<const Foo>

  - by Blair Zajac

  Silly question, but say you have class Foo: class Foo { public: typedef boost::shared_ptr<Foo> RcPtr; void non_const_method() {} void const_method() const {} }; Having a const Foo::RcPtr doesn't prevent non-const methods from being invoked on the class, the following will compile: #include <boost/shared_ptr.hpp> int main() { const Foo::RcPtr const_foo_ptr(new Foo); const_foo_ptr->non_const_method(); const_foo_ptr->const_method(); return 0; } But naming a typedef ConstRcPtr implies, to me, that the typedef would be typedef const boost::shared_ptr<Foo> ConstRcPtr; which is not what I'm interested in. An odder name, but maybe more accurate, is RcPtrConst: typedef boost::shared_ptr<const Foo> RcPtrConst; However, Googling for RcPtrConst gets zero hits, so people don't use this as a typedef name :) Does anyone have any other suggestions?

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• Setting up boost filesystem

  - by brit

  I've been having serious problems trying to set up boost. I must have installed and uninstalled the libraries a dozen times. In my most recent attempt, I followed these instructions: Download the zip and unzip it. Get the prebuilt jam executable and unzip it. Put that directory in your path. (Edit Path by using Control Panel...System..Advanced....Environemnt Variables) Open Visual Studio command prompt. Browse to boost directory. Run: bjam "-sTOOLS=vc-8_0" install The main reason I'm trying to use boost is for boost/filesystem yet nothing is working. I know this question has been asked before, but it only resulted in more errors.. Please Help!

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• Question on boost array initializer

  - by ArunSaha

  I am trying to understand the boost array. The code can be read easily from author's site. In the design rationale, author (Nicolai M. Josuttis) mentioned that the following two types of initialization is possible. boost::array<int,4> a = { { 1, 2, 3 } }; // Line 1 boost::array<int,4> a = { 1, 2, 3 }; // Line 2 In my experiment with g++ (version 4.1.2) Line 1 is working but Line 2 is not. (Line 2 yields the following: warning: missing braces around initializer for 'int [4]' warning: missing initializer for member 'boost::array<int, 4ul>::elems' ) Nevertheless, my main question is, how Line 1 is working? I tried to write a class similar to array.hpp and use statement like Line 1, but that did not work :-(. Can somebody explain me? Is there some boost specific thing happening in Line 1 that I need to be aware of? Thanks in advance. Regards,

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• insert multiple elements in string in python

  - by Anurag Sharma

  I have to build a string like this { name: "john", url: "www.dkd.com", email: "[email protected]" } where john, www.dkd.com and [email protected] are to be supplied by variables I tried to do the following s1 = "{'name:' {0},'url:' {1},'emailid:' {2}}" s1.format("john","www.dkd.com","[email protected]") I am getting the following error Traceback (most recent call last): File "<stdin>", line 1, in <module> KeyError: "'name" Dont able to understand what I am doing wrong

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