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• Calling private constructors with Reflection.Emit?

  - by Jakob Botsch Nielsen

  I'm trying to emit the following IL: LocalBuilder pointer = il.DeclareLocal(typeof(IntPtr)); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Stloc, pointer); il.Emit(OpCodes.Ldloca, pointer); il.Emit(OpCodes.Call, typeof(IntPtr).GetMethod("ToPointer")); il.Emit(OpCodes.Ret); The delegate I bind with has the signature void* TestDelegate(IntPtr ptr) It throws the exception Operation could destabilize the runtime. Anyone knows what's wrong? EDIT: Alright, so I got the IL working now. The entire goal of this was to be able to call a private constructor. The private constructor takes a pointer so I can't use normal reflection. Now.. When I call it, I get an exception saying Attempt by method <built method> to access method <private constructor> failed. Apparently it's performing security checks - but from experience I know that Reflection is able to do private stuff like this normally, so hopefully there is a way to disable that check?

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• _beginthreadx and socket

  - by user638197

  hi, i have a question about the _beginthreadx function In the third and fourth parameter: if i have this line to create the thread hThread=(HANDLE)_beginthreadex(0,0, &RunThread, &m_socket,CREATE_SUSPENDED,&threadID ); m_socket is the socket that i want inside the thread (fourth parameter) and i have the RunThread function (third parameter) in this way static unsigned __stdcall RunThread (void* ptr) { return 0; } It is sufficient to create the thread independently if m_socket has something or not? Thanks in advance Thank you for the response Ciaran Keating helped me understand better the thread I'll explain a little more the situation I´m creating the tread in this function inside a class public: void getClientsConnection() { numberOfClients = 1; SOCKET temporalSocket = NULL; firstClient = NULL; secondClient = NULL; while (numberOfClients < 2) { temporalSocket = SOCKET_ERROR; while (temporalSocket == SOCKET_ERROR) { temporalSocket = accept(m_socket, NULL, NULL); //----------------------------------------------- HANDLE hThread; unsigned threadID; hThread=(HANDLE)_beginthreadex(0,0, &RunThread, &m_socket,CREATE_SUSPENDED,&threadID ); WaitForSingleObject( hThread, INFINITE ); if(!hThread) printf("ERROR AL CREAR EL HILO: %ld\n", WSAGetLastError()); //----------------------------------------------- } if(firstClient == NULL) { firstClient = temporalSocket; muebleC1 = temporalSocket; actionC1 = temporalSocket; ++numberOfClients; printf("CLIENTE 1 CONECTADO\n"); } else { secondClient = temporalSocket; muebleC2 = temporalSocket; actionC2 = temporalSocket; ++numberOfClients; printf("CLIENTE 2 CONECTADO\n"); } } } What i'm trying to do is to have the socket inside the thread while wait for a client connection Is this feasible as i have the code of the thread? I can change the state of the thread that is not a problem Thanks again

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• Sorting by key > 10 integer sequences. with thrust

  - by smilingbuddha

  I want to perform a sort_by_key where I have a single key-sequence and multiple value sequences. One usually performs this with sort_by_key( key, key + N, make_zip_iterator( make_tuple(x1 , x2 , ...) ) ) However I want to perform a sort with 10 sequences each of length N. Thrust does not support tuples of size = 10. So is there a way around this ? Of course one can keep a separate copy of the key vector and perform sorts on bunches of 10 sequences. But I would like to do everything in a single call.

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• Problem overridding virtual function

  - by William

  Okay, I'm writing a game that has a vector of a pairent class (enemy) that s going to be filled with children classes (goomba, koopa, boss1) and I need to make it so when I call update it calls the childclasses respective update. I have managed to create a example of my problem. #include <stdio.h> class A{ public: virtual void print(){printf("Hello from A");} }; class B : public A{ public: void print(){printf("Hello from B");} }; int main(){ A ab = B(); ab.print(); while(true){} } Output wanted: "Hello from B" Output got: "Hello from A" How do I get it to call B's print function?

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• How to make negate_unary work with any type?

  - by Chan

  Hi, Following this question: How to negate a predicate function using operator ! in C++? I want to create an operator ! can work with any functor that inherited from unary_function. I tried: template<typename T> inline std::unary_negate<T> operator !( const T& pred ) { return std::not1( pred ); } The compiler complained: Error 5 error C2955: 'std::unary_function' : use of class template requires template argument list c:\program files\microsoft visual studio 10.0\vc\include\xfunctional 223 1 Graphic Error 7 error C2451: conditional expression of type 'std::unary_negate<_Fn1>' is illegal c:\program files\microsoft visual studio 10.0\vc\include\ostream 529 1 Graphic Error 3 error C2146: syntax error : missing ',' before identifier 'argument_type' c:\program files\microsoft visual studio 10.0\vc\include\xfunctional 222 1 Graphic Error 4 error C2065: 'argument_type' : undeclared identifier c:\program files\microsoft visual studio 10.0\vc\include\xfunctional 222 1 Graphic Error 2 error C2039: 'argument_type' : is not a member of 'std::basic_ostream<_Elem,_Traits>::sentry' c:\program files\microsoft visual studio 10.0\vc\include\xfunctional 222 1 Graphic Error 6 error C2039: 'argument_type' : is not a member of 'std::basic_ostream<_Elem,_Traits>::sentry' c:\program files\microsoft visual studio 10.0\vc\include\xfunctional 230 1 Graphic Any idea? Update Follow "templatetypedef" solution, I got new error: Error 3 error C2831: 'operator !' cannot have default parameters c:\visual studio 2010 projects\graphic\graphic\main.cpp 39 1 Graphic Error 2 error C2808: unary 'operator !' has too many formal parameters c:\visual studio 2010 projects\graphic\graphic\main.cpp 39 1 Graphic Error 4 error C2675: unary '!' : 'is_prime' does not define this operator or a conversion to a type acceptable to the predefined operator c:\visual studio 2010 projects\graphic\graphic\main.cpp 52 1 Graphic Update 1 Complete code: #include <iostream> #include <functional> #include <utility> #include <cmath> #include <algorithm> #include <iterator> #include <string> #include <boost/assign.hpp> #include <boost/assign/std/vector.hpp> #include <boost/assign/std/map.hpp> #include <boost/assign/std/set.hpp> #include <boost/assign/std/list.hpp> #include <boost/assign/std/stack.hpp> #include <boost/assign/std/deque.hpp> struct is_prime : std::unary_function<int, bool> { bool operator()( int n ) const { if( n < 2 ) return 0; if( n == 2 || n == 3 ) return 1; if( n % 2 == 0 || n % 3 == 0 ) return 0; int upper_bound = std::sqrt( static_cast<double>( n ) ); for( int pf = 5, step = 2; pf <= upper_bound; ) { if( n % pf == 0 ) return 0; pf += step; step = 6 - step; } return 1; } }; /* template<typename T> inline std::unary_negate<T> operator !( const T& pred, typename T::argument_type* dummy = 0 ) { return std::not1<T>( pred ); } */ inline std::unary_negate<is_prime> operator !( const is_prime& pred ) { return std::not1( pred ); } template<typename T> inline void print_con( const T& con, const std::string& ms = "", const std::string& sep = ", " ) { std::cout << ms << '\n'; std::copy( con.begin(), con.end(), std::ostream_iterator<typename T::value_type>( std::cout, sep.c_str() ) ); std::cout << "\n\n"; } int main() { using namespace boost::assign; std::vector<int> nums; nums += 1, 3, 5, 7, 9; nums.erase( remove_if( nums.begin(), nums.end(), !is_prime() ), nums.end() ); print_con( nums, "After remove all primes" ); } Thanks, Chan Nguyen

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• Fast, Vectorizable method of taking floating point number modulus of special primes?

  - by caffiend

  Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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• extraneous calls to copy-constructor and destructor

  - by eSKay

  [This question is a follow up to this question] class A { public: A() {cout<<"A Construction" <<endl;} A(A const& a){cout<<"A Copy Construction"<<endl;} ~A() {cout<<"A Destruction" <<endl;} }; int main() { { vector<A> t; t.push_back(A()); t.push_back(A()); // once more } } The output is: A Construction // 1 A Copy Construction // 1 A Destruction // 1 A Construction // 2 A Copy Construction // 2 A Copy Construction // WHY THIS? A Destruction // 2 A Destruction // deleting element from t A Destruction // deleting element from t A Destruction // WHY THIS?

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• Matlab Question - Principal Component Analysis

  - by Jack

  I have a set of 100 observations where each observation has 45 characteristics. And each one of those observations have a label attached which I want to predict based on those 45 characteristics. So it's an input matrix with the dimension 45 x 100 and a target matrix with the dimension 1 x 100. The thing is that I want to know how many of those 45 characteristics are relevant in my set of data, basically the principal component analysis, and I understand that I can do this with Matlab function processpca. Could you please tell me how can I do this? Suppose that the input matrix is x with 45 rows and 100 columns and y is a vector with 100 elements.

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• c++ library for endian-aware reading of raw file stream metadata?

  - by Kache4

  I've got raw data streams from image files, like: vector<char> rawData(fileSize); ifstream inFile("image.jpg"); inFile.read(&rawData[0]); I want to parse the headers of different image formats for height and width. Is there a portable library that can can read ints, longs, shorts, etc. from the buffer/stream, converting for endianess as specified? I'd like to be able to do something like: short x = rawData.readLeShort(offset); or long y = rawData.readBeLong(offset) An even better option would be a lightweight & portable image metadata library (without the extra weight of an image manipulation library) that can work on raw image data. I've found that Exif libraries out there don't support png and gif.

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• How to interpolate rotations?

  - by uhuu

  I have two vectors describing rotations; a start rotation A and a target rotation B. How would I best go about interpolating A by a factor F to approach B? Using a simple lerp on the vectors fails to work when more than one dimension needs to be interpolated (i.e. produces undesirable rotations). Maybe building quaternions from the rotation vectors and using slerp is the way to go. But how, then, could I extract a vector describing the new rotation from the resulting quaternion? Thanks in advance.

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• problems with matlab wavrecord and wavread

  - by user504363

  Hi all I have a problem in matlab I want to record a speech for 2 seconds then read the recorded sound and plot it I use the code FS = 8000; new_wav = wavrecord(2*FS,FS,'int16'); x = wavread(new_wav); plot(x); but the error appears ??? Error using ==> fileparts at 20 Input must be a row vector of characters. Error in ==> wavread>open_wav at 193 [pat,nam,ext] = fileparts(file); Error in ==> wavread at 65 [fid,msg] = open_wav(file); Error in ==> test at 2 x = wavread(new_wav); I plotted correctly recorded sound files, but when I want to record new one through matlab I get this errors. I tried many ways by changing FS and 'int16' but nothing happens. thanks

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• How might I assume a "default value" when parsing using boost::spirit?

  - by tJener

  Let's say I have a grammar defined to something like: a b c d where c, and d are optional and default to 14 if not given. Can I get it to automatically return the 14 if the value isn't given? The closest I've come is like the following: qi::rule<Iterator, std::vector<int>(), ascii::space_type> some_rule; some_rule %= >> int_ >> int_ >> -int_ >> -int_; // ... some_other_rule = some_rule[&some_callback_for_int_vectors]; which will then get 0 for the optional values that didn't show up (I believe). I then change consecutive 0s at the end into 14. Not only is this horribly wrong, but its also just not elegant. Is there a better way to do this?

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• Can I write functors using a private nested struct?

  - by Kristo

  Given this class: class C { private: struct Foo { int key1, key2, value; }; std::vector<Foo> fooList; }; The idea here is that fooList can be indexed by either key1 or key2 of the Foo struct. I'm trying to write functors to pass to std::find so I can look up items in fooList by each key. But I can't get them to compile because Foo is private within the class (it's not part of C's interface). Is there a way to do this without exposing Foo to the rest of the world? (note: I've got to run to a meeting. I'll be able to post more sample code in about a half hour.)

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• WPF tabswitch/ render takes too much time..

  - by Socrates

  I have a WPF application with many tabs.. in one tab.. i make a verycomplex vector drawing consisting of thousands of drawing visuals.. (this represents a machine and all elements need to be interactable..) It takes 3/4 seconds for drawing this for the first time..After the first draw it should be done.. The problem is if i switch to another tab and comeback, it takes atlease 2,3 seconds to show the tabpage with drawing again.. Since there is no redraw, why should it take so much time..?

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• Uniform distribution of binary values in Matlab

  - by JohnIdol

  I have a requirement for the generation of a given number N of vectors of given size each consistent of a uniform distribution of 0s and 1s. This is what I am doing at the moment, but I noticed that the distribution is strongly peaked at half 1s and half 0s, which is no good for what I am doing: a = randint(1, sizeOfVector, [0 1]); The unifrnd function looks promising for what I need, but I can't manage to understand how to output a binary vector of that size. Is it the case that I can use the unifrnd function (and if so how would be appreciated!) or can is there any other more convenient way to obtain such a set of vectors? Any help appreciated!

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• .NET framework execution aborted while executing CLR stored procedure?

  - by Sean Ochoa

  I constructed a stored procedure that does the equivalent of FOR XML AUTO in SQL Server 2008. Now that I'm testing it, it gives me a really unhelpful error message. What does this error mean? Msg 10329, Level 16, State 49, Procedure ForXML, Line 0 .NET Framework execution was aborted. System.Threading.ThreadAbortException: Thread was being aborted. System.Threading.ThreadAbortException: at System.Runtime.InteropServices.Marshal.PtrToStringUni(IntPtr ptr, Int32 len) at System.Data.SqlServer.Internal.CXVariantBase.WSTRToString() at System.Data.SqlServer.Internal.SqlWSTRLimitedBuffer.GetString(SmiEventSink sink) at System.Data.SqlServer.Internal.RowData.GetString(SmiEventSink sink, Int32 i) at Microsoft.SqlServer.Server.ValueUtilsSmi.GetValue(SmiEventSink_Default sink, ITypedGettersV3 getters, Int32 ordinal, SmiMetaData metaData, SmiContext context) at Microsoft.SqlServer.Server.ValueUtilsSmi.GetValue200(SmiEventSink_Default sink, SmiTypedGetterSetter getters, Int32 ordinal, SmiMetaData metaData, SmiContext context) at System.Data.SqlClient.SqlDataReaderSmi.GetValue(Int32 ordinal) at System.Data.SqlClient.SqlDataReaderSmi.GetValues(Object[] values) at System.Data.ProviderBase.DataReaderContainer.CommonLanguageSubsetDataReader.GetValues(Object[] values) at System.Data.ProviderBase.SchemaMapping.LoadDataRow() at System.Data.Common.DataAdapter.FillLoadDataRow(SchemaMapping mapping) at System.Data.Common.DataAdapter.FillFromReader(DataSet dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue) at System.Data.Common.DataAdapter.Fill(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords) at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior) at System.Data.Common.DbDataAdapter.Fill(DataTable dataTable) at ForXML.GetXML...

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• RODBC string getting truncated

  - by sayan dasgupta

  Hi all, I am fetching data from MySql Server into R using RODBC. So in one column of the database is a character vector SELECT MAX(CHAR_LENGTH(column)) FROM reqtable; RETURNS 26566 Now I will show you an example how I am running into the problem `library(RODBC) con <- odbcConnect("mysqlcon") rslts <- as.numeric(sqlQuery(con, "SELECT CHAR_LENGTH(column) FROM reqtable LIMIT 10", as.is=TRUE)[,1]) ` returns > rslts [1] 62 31 17 103 30 741 28 73 25 357 where as rslts <- nchar(as.character(sqlQuery(con, "SELECT column FROM reqtable LIMIT 10", as.is=TRUE)[,1])) returns > rslts [1] 62 31 17 103 30 255 28 73 25 255 So strings with length 255 is getting truncated at 255. Is there a way I can get the full string. Thanks

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• CSV parser in C++

  - by User1

  All I need is a good CSV file parser for C++. At this point it can really just be a comma-delimited parser (ie don't worry about escaping new lines and commas). The main need is a line-by-line parser that will return a vector for the next line each time the method is called. I found this article which looks quite promising: http://www.boost.org/doc/libs/1_35_0/libs/spirit/example/fundamental/list_parser.cpp I've never used Boost's Spirit, but am willing to try it. Is it overkill/bloated or is it fast and efficient? Does anyone have faster algorithms using STL or anything else? Thanks!

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• Distance between hyperplanes

  - by michael dillard

  I'm trying to teach myself some machine learning, and have been using the MNIST database (http://yann.lecun.com/exdb/mnist/) do so. The author of that site wrote a paper in '98 on all different kinds of handwriting recognition techniques, available at http://yann.lecun.com/exdb/publis/pdf/lecun-98.pdf. The 10th method mentioned is a "Tangent Distance Classifier". The idea being that if you place each image in a (NxM)-dimensional vector space, you can compute the distance between two images as the distance between the hyperplanes formed by each where the hyperplane is given by taking the point, and rotating the image, rescaling the image, translating the image, etc. I can't figure out enough to fill in the missing details. I understand that most of these are indeed linear operators, so how does one use that fact to then create the hyperplane? And once we have a hyperplane, how do we take its distance with other hyperplanes?

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• C++ refactor common code with one different statement

  - by user231536

  I have two methods f(vector<int>& x, ....) and g(DBConn& x, ....) where the (....) parameters are all identical. The code inside the two methods are completely identical except for one statement where we do different actions based on the type of x: in f(): we do x.push_back(i) in g(): we do x.DeleteRow(i) What is the simplest way to extract the common code into one method and yet have the two different statements? I am thinking of having a templated functor that overloads operator () (int a) but that seems overkill.

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• Read multiple strings from a file C++

  - by user69514

  Hi I need to read different values stored in a file one by one. So I was thinking I can use ifstream to open the file, but since the file is set up in such a way that a line might contain three numbers, and the other line one number or two numbers I'm not sure how to read each number one by one. I was thinking of using stringstream but I'm not sure if that would work. The file is a format like this. 52500.00 64029.50 56000.00 65500.00 53780.00 77300.00 44000.50 80100.20 90000.00 41000.00 60500.50 72000.00 I need to read each number and store it in a vector. What is the best way to accomplish this? Reading one number at a time even though each line contains a different amount of numbers?

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• Multiplying Block Matrices in Numpy

  - by Ada Xu

  Hi Everyone I am python newbie I have to implement lasso L1 regression for a class assignment. This involves solving a quadratic equation involving block matrices. minimize x^t * H * x + f^t * x where x 0 Where H is a 2 X 2 block matrix with each element being a k dimensional matrix and x and f being a 2 X 1 vectors each element being a k dimension vector. I was thinking of using nd arrays. such that np.shape(H) = (2, 2, k, k) np.shape(x) = (2, k) But I figured out that np.dot(X, H) doesn't work here. Is there an easy way to solve this problem? Thanks in advance.

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• CURL C API: callback was not called

  - by Pierre

  Hi all, The code below is a test for the CURL C API . The problem is that the callback function write_callback is never called. Why ? /** compilation: g++ source.cpp -lcurl */ #include <assert.h> #include <iostream> #include <cstdlib> #include <cstring> #include <cassert> #include <curl/curl.h> using namespace std; static size_t write_callback(void *ptr, size_t size, size_t nmemb, void *userp) { std::cerr << "CALLBACK WAS CALLED" << endl; exit(-1); return size*nmemb; } static void test_curl() { int any_data=1; CURLM* multi_handle=NULL; CURL* handle_curl = ::curl_easy_init(); assert(handle_curl!=NULL); ::curl_easy_setopt(handle_curl, CURLOPT_URL, "http://en.wikipedia.org/wiki/Main_Page"); ::curl_easy_setopt(handle_curl, CURLOPT_WRITEDATA, &any_data); ::curl_easy_setopt(handle_curl, CURLOPT_VERBOSE, 1); ::curl_easy_setopt(handle_curl, CURLOPT_WRITEFUNCTION, write_callback); ::curl_easy_setopt(handle_curl, CURLOPT_USERAGENT, "libcurl-agent/1.0"); multi_handle = ::curl_multi_init(); assert(multi_handle!=NULL); ::curl_multi_add_handle(multi_handle, handle_curl); int still_running=0; /* lets start the fetch */ while(::curl_multi_perform(multi_handle, &still_running) == CURLM_CALL_MULTI_PERFORM ); std::cerr << "End of curl_multi_perform."<< endl; //cleanup should go here ::exit(EXIT_SUCCESS); } int main(int argc,char** argv) { test_curl(); return 0; } Many thanks Pierre

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• Reducing template bloat with inheritance

  - by benoitj

  Does anyone have experience reducing template code bloat using inheritance? i hesitate rewriting our containers this way: class vectorBase { public: int size(); void clear(); int m_size; void *m_rawData; //.... }; template< typename T > class vector : public vectorBase { void push_back( const T& ); //... }; I should keep maximum performance while reducing compile time I'm also wondering why stl implementations do not uses this approach Thanks for your feedbacks

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• do.call(rbind, list) for uneven number of column

  - by h.l.m

  I have a list, with each element being a character vector, of differing lengths I would like to bind the data as rows, so that the column names 'line up' and if there is extra data then create column and if there is missing data then create NAs Below is a mock example of the data I am working with x <- list() x[[1]] <- letters[seq(2,20,by=2)] names(x[[1]]) <- LETTERS[c(1:length(x[[1]]))] x[[2]] <- letters[seq(3,20, by=3)] names(x[[2]]) <- LETTERS[seq(3,20, by=3)] x[[3]] <- letters[seq(4,20, by=4)] names(x[[3]]) <- LETTERS[seq(4,20, by=4)] The below line would normally be what I would do if I was sure that the format for each element was the same... do.call(rbind,x) I was hoping that someone had come up with a nice little solution that matches up the column names and fills in blanks with NAs whilst adding new columns if in the binding process new columns are found...

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