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  • Should I call class destructor in this code?

    - by peterg
    I am using this sample to decode/encode some data I am retrieving/sending from/to a web server, and I want to use it like this: BOOL HandleMessage(UINT uMsg,WPARAM wParam,LPARAM lParam,LRESULT* r) { if(uMsg == WM_DESTROY) { PostQuitMessage(0); return TRUE; } else if(uMsg == WM_CREATE) { // Start timer StartTimer(); return TRUE; } else if(uMsg == WM_TIMER) { //get data from server char * test = "test data"; Base64 base64; char *temp = base64.decode(test); MessageBox(TEXT(temp), 0, 0); } } The timer is set every 5 minutes. Should I use delete base64 at the end? Does delete deallocates everything used by base64?

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  • Why freed struct in C still has data?

    - by kliketa
    When I run this code: #include <stdio.h> typedef struct _Food { char name [128]; } Food; int main (int argc, char **argv) { Food *food; food = (Food*) malloc (sizeof (Food)); snprintf (food->name, 128, "%s", "Corn"); free (food); printf ("%d\n", sizeof *food); printf ("%s\n", food->name); } I still get 128 Corn although I have freed food. Why is this? Is memory really freed?

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  • [C++] Wrong EOF when unzipping binary file

    - by djzmo
    Hello there, I tried to unzip a binary file to a membuf from a zip archive using Lucian Wischik's Zip Utils: http://www.wischik.com/lu/programmer/zip_utils.html http://www.codeproject.com/KB/files/zip_utils.aspx FindZipItem(hz, filename.c_str(), true, &j, &ze); char *content = new char[ze.unc_size]; UnzipItem(hz, j, content, ze.unc_size); delete[] content; But it didn't unzip the file correctly. It stopped at the first 0x00 of the file. For example when I unzip an MP3 file, it will only unzip the first 4 bytes: 0x49443303 (ID3\0) because the 5th to 8th byte is 0x00000000. I also tried to capture the ZR_RESULT, and it always return ZR_OK (which means completed without errors). I think this guy also had the same problem, but no one replied to his question: http://www.codeproject.com/KB/files/zip_utils.aspx?msg=2876222#xx2876222xx Any kind of help would be appreciated :)

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  • C pointer array scope and function calls

    - by juvenis
    I have this situation: { float foo[10]; for (int i = 0; i < 10; i++) { foo[i] = 1.0f; } object.function1(foo); // stores the float pointer to a const void* member of object } object.function2(); // uses the stored void pointer Are the contents of the float pointer unknown in the second function call? It seems that I get weird results when I run my program. But if I declare the float foo[10] to be const and initialize it in the declaration, I get correct results. Why is this happening?

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  • Multiset of shared_ptrs as a dynamic priority queue: Concept and practice

    - by Sarah
    I was using a vector-based priority queue typedef std::priority_queue< Event, vector< Event >, std::greater< Event > > EventPQ; to manage my Event objects. Now my simulation has to be able to find and delete certain Event objects not at the top of the queue. I'd like to know if my planned work-around can do what I need it to, and if I have the syntax right. I'd also like to know if dramatically better solutions exist. My plan is to make EventPQ a multiset of smart pointers to Event objects: typedef std::multi_set< boost::shared_ptr< Event > > EventPQ; I'm borrowing functions of the Event class from a related post on a multimap priority queue. // Event.h #include <cstdlib> using namespace std; #include <set> #include <boost/shared_ptr.hpp> class Event; typedef std::multi_set< boost::shared_ptr< Event > > EventPQ; class Event { public: Event( double t, int eid, int hid ); ~Event(); void add( EventPQ& q ); void remove(); bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } bool operator > ( const Event & rhs ) const { return ( time > rhs.time ); } double time; int eventID; int hostID; EventPQ* mq; EventPQ::iterator mIt; }; // Event.cpp Event::Event( double t, int eid, int hid ) { time = t; eventID = eid; hostID = hid; } Event::~Event() {} void Event::add( EventPQ& q ) { mq = &q; mIt = q.insert( boost::shared_ptr<Event>(this) ); } void Event::remove() { mq.erase( mIt ); mq = 0; mIt = EventPQ::iterator(); } I was hoping that by making EventPQ a container of pointers, I could avoid wasting time copying Events into the container and avoid accidentally editing the wrong copy. Would it be dramatically easier to store the Events themselves in EventPQ instead? Does it make more sense to remove the time keys from Event objects and use them instead as keys in a multimap? Assuming the current implementation seems okay, my questions are: Do I need to specify how to sort on the pointers, rather than the objects, or does the multiset automatically know to sort on the objects pointed to? If I have a shared_ptr ptr1 to an Event that also has a pointer in the EventPQ container, how do I find and delete the corresponding pointer in EventPQ? Is it enough to .find( ptr1 ), or do I instead have to find by the key (time)? Is the Event::remove() sufficient for removing the pointer in the EventPQ container? There's a small chance multiple events could be created with the same time (obviously implied in the use of multiset). If the find() works on event times, to avoid accidentally deleting the wrong event, I was planning to throw in a further check on eventID and hostID. Does this seem reasonable? (Dumb syntax question) In Event.h, is the declaration of dummy class Event;, then the EventPQ typedef, and then the real class Event declaration appropriate? I'm obviously an inexperienced programmer with very spotty background--this isn't for homework. Would love suggestions and explanations. Please let me know if any part of this is confusing. Thanks.

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  • error in encryption program

    - by Raja
    #include<iostream> #include<math.h> #include<string> using namespace std; int gcd(int n,int m) { if(m<=n && n%m ==0) return m; if(n<m) return gcd(m,n); else return gcd(m,n%m); } int REncryptText(char m) { int p = 11, q = 3; int e = 3; int n = p * q; int phi = (p - 1) * (q - 1); int check1 = gcd(e, p - 1); int check2 = gcd(e, q - 1); int check3 = gcd(e, phi); // // Compute d such that ed = 1 (mod phi) //i.e. compute d = e-1 mod phi = 3-1 mod 20 //i.e. find a value for d such that phi divides (ed-1) //i.e. find d such that 20 divides 3d-1. //Simple testing (d = 1, 2, ...) gives d = 7 // double d = Math.Pow(e, -1) % phi; int d = 7; // public key = (n,e) // (33,3) //private key = (n,d) //(33 ,7) double g = pow(m,e); int ciphertext = g %n; // Now say we want to encrypt the message m = 7, c = me mod n = 73 mod 33 = 343 mod 33 = 13. Hence the ciphertext c = 13. //double decrypt = Math.Pow(ciphertext, d) % n; return ciphertext; } int main() { char plaintext[80],str[80]; cout<<" enter the text you want to encrpt"; cin.get(plaintext,79); int l =strlen(plaintext); for ( int i =0 ; i<l ; i++) { char s = plaintext[i]; str[i]=REncryptText(s); } for ( int i =0 ; i<l ; i++) { cout<<"the encryption of string"<<endl; cout<<str[i]; } return 0; }

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  • Hiredis waiting for message

    - by Vivek Goel
    I am using hiredis C library to connect to redis server. I am not able to figure out how to wait for new messages after subscribing to new message. My code look like: signal(SIGPIPE, SIG_IGN ); struct event_base *base = event_base_new(); redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379); if (c->err) { /* Let *c leak for now... */ printf("Error: %s\n", c->errstr); return 1; } redisLibeventAttach(c, base); redisAsyncSetConnectCallback(c, connectCallback); redisAsyncSetDisconnectCallback(c, disconnectCallback); redisAsyncCommand(c, NULL, NULL, "SET key %b", argv[argc - 1], strlen(argv[argc - 1])); redisAsyncCommand(c, getCallback, (char*) "end-1", "GET key"); redisAsyncCommand(c, getCallback, (char*) "end-1", "SUBSCRIBE foo"); Now how to tell hiredis to wait for message on channel ?

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  • How to use a object whose copy constructor and copy assignment is private?

    - by coanor
    In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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  • help me with xor encryption in c#

    - by x86shadow
    I wrote this code in c# to encrypt a text with a key : using System; using System.Linq; using System.Collections.Generic; using System.Text; namespace ENCRYPT { class XORENC { private static int Bin2Dec(string num) { int _num = 0; for (int i = 0; i < num.Length; i++) { _num += (int)Math.Pow(2, num.Length - i - 1) * int.Parse(num[i].ToString()); } return _num; } private static string Dec2Bin(int num) { if (num < 2) return num.ToString(); return Dec2Bin(num / 2) + (num % 2).ToString(); } public static string StrXor(string str, string key) { string _str = ""; string _key = ""; string _dec = ""; string _temp = ""; for (int i = 0; i < str.Length; i++) { _temp = Dec2Bin(str[i]); for (int j = 0; j < 8 - _temp.Length + 1; j++) { _temp = '0' + _temp; } _str += _temp; } for (int i = 0; i < key.Length; i++) { _temp = Dec2Bin(key[i]); for (int j = 0; j < 8 - _temp.Length + 1; j++) { _temp = '0' + _temp; } _key += _temp; } while (_key.Length < _str.Length) { _key += _key; } if (_key.Length > _str.Length) _key = _key.Substring(0, _str.Length); for (int i = 0; i < _str.Length; i++) { if (_str[i] == _key[i]) { _dec += '0'; } else { _dec += '1'; } } _str = ""; for (int i = 0; i < _dec.Length; i = i + 8) { char _chr = (char)0; _chr = (char)Bin2Dec(_dec.Substring(i, 8)); _str += _chr; } return _str; } } } the problem is that I always get error when I want to decrypt an encryted text with this code. see the example below for more info : string enc_text = ENCRYPT.XORENC("abc","a"); //enc_text = " ??" string dec_text = ENCRYPT.XORENC(enc_text,"a"); //ERROR any one can help ?

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  • How return a std::string from C's "getcwd" function

    - by rubenvb
    Sorry to keep hammering on this, but I'm trying to learn :). Is this any good? And yes, I care about memory leaks. I can't find a decent way of preallocating the char*, because there simply seems to be no cross-platform way. const string getcwd() { char* a_cwd = getcwd(NULL,0); string s_cwd(a_cwd); free(a_cwd); return s_cwd; } UPDATE2: without Boost or Qt, the most common stuff can get long-winded (see accepted answer)

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  • some logical error in taking up character in java

    - by Himanshu Aggarwal
    This is my code... class info{ public static void main (String[]args) throws IOException{ char gen; while(true) { //problem occurs with this while System.out.print("\nENTER YOUR GENDER (M/F) : "); gen=(char)System.in.read(); if(gen=='M' || gen=='F' || gen=='m' || gen=='f'){ break; } } System.out.println("\nGENDER = "+gen); } } This is my output... ENTER YOUR GENDER (M/F) : h ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : ENTER YOUR GENDER (M/F) : m GENDER = m Could someone please help me understand why it is asking for the gender so many times.

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  • Haskell. Numbers in binary numbers. words

    - by Katja
    Hi! I need to code words into binary numbers. IN: "BCD..." OUT:1011... I have written already funktion for coding characters into siple numbers IN: 'C' OUT: 3 IN: 'c' OUT: 3 lett2num :: Char -> Int lett2num x | (ord 'A' <= ord x) && (ord x <= ord 'Z') = (ord x - ord 'A') + 1 | (ord 'a' <= ord x) && (ord x <= ord 'z') = (ord x - ord 'a') +1 num2lett :: Int -> Char num2lett n | (n <= ord 'A') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) | (n <= ord 'a') && (n <= ord 'Z') = chr(ord 'A'+ n - 1) I wrote as well function for codind simple numbers into binary. num2bin :: Int->[Int] num2bin 0 = [] num2bin n | n>=0 = n `mod` 2 : (num2bin( n `div` 2)) | otherwise = error but I donw want those binary numbers to be in a list how can I get rid of the lists? Thanks

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  • How to return a string literal from a function

    - by skydoor
    Hi I am always confused about return a string literal or a string from a function. I was told that there might be memory leak because you don't know when the memory will be deleted? For example, in the code below, how to implement foo() so that make the output of the code is "Hello World"? void foo ( ) // you can add parameters here. { } int main () { char *c; foo ( ); printf ("%s",c); return 0; } Also if the return type of foo() is not void, but you can return char*, what should it be.

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  • How to sanely read and dump structs to disk when some fields are pointers?

    - by bp
    Hello, I'm writing a FUSE plugin in C. I'm keeping track of data structures in the filesystem through structs like: typedef struct { block_number_t inode; filename_t filename; //char[SOME_SIZE] some_other_field_t other_field; } fs_directory_table_item_t; Obviously, I have to read (write) these structs from (to) disk at some point. I could treat the struct as a sequence of bytes and do something like this: read(disk_fd, directory_table_item, sizeof(fs_directory_table_item_t)); ...except that cannot possibly work as filename is actually a pointer to the char array. I'd really like to avoid having to write code like: read(disk_df, *directory_table_item.inode, sizeof(block_number_t)); read(disk_df, directory_table_item.filename, sizeof(filename_t)); read(disk_df, *directory_table_item.other_field, sizeof(some_other_field_t)); ...for each struct in the code, because I'd have to replicate code and changes in no less than three different places (definition, reading, writing). Any DRYer but still maintainable ideas?

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  • Assigning large UInt32 constants in VB.Net

    - by Kumba
    I inquired on VB's erratic behavior of treating all numerics as signed types back in this question, and from the accepted answer there, was able to get by. Per that answer: Visual Basic Literals Also keep in mind you can add literals to your code in VB.net and explicitly state constants as unsigned. So I tried this: Friend Const POW_1_32 As UInt32 = 4294967296UI And VB.NET throws an Overflow error in the IDE. Pulling out the integer overflow checks doesn't seem to help -- this appears to be a flaw in the IDE itself. This, however, doesn't generate an error: Friend Const POW_1_32 As UInt64 = 4294967296UL So this suggests to me that the IDE isn't properly parsing the code and understanding the difference between Int32 and UInt32. Any suggested workarounds and/or possible clues on when MS will make unsigned data types intrinsic to the framework instead of the hacks they currently are?

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  • What am I encrypting wrong here?

    - by Katie Krueger
    So I have a wordplay project to do and I have to encrypt some characters. I am at the point where I am stuck, and when I run it and type 1 for encrypt it doesn't shift that many letters. It just prints the work over again. I am wondering what I could do to fix it where if I say "hello" it will print 1 character over and say "ifmmp" Thank you! import java.util.Scanner; public class WordPlayTester{ public static void main(String [] args){ String word, reverse=""; String original; int key= 0; String Menu= "1-Encrypt \n2-Decrypt \n3-Is Palindrome \n0-Quit \n-Select an option-"; Scanner in = new Scanner(System.in); System.out.println("-Type any word-"); word = in.nextLine(); System.out.println(Menu); int choice=in.nextInt(); if(choice==1) { System.out.println("Insert a Key number"); int select= in.nextInt(); for (int i=0; i < word.length(); i++) { char c = word.charAt(i); if (c >= 'A' && c <= 'Z') { c = (char)(c - 64); int n = c+1; n = n % 26; if (n < 0) { n = n + 26; } c = (char)(n + 65); } System.out.println(c); } } else if(choice==3) { int length = word.length(); for ( int i = length - 1 ; i >= 0 ; i-- ) reverse = reverse + word.charAt(i); if (word.equals(reverse)) System.out.println("Your word is a palindrome."); else System.out.println("Your word is not a palindrome."); } else if(choice==0) { System.exit(0); } else { System.out.println(Menu); } } }

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  • number of months between two dates - using boost's date

    - by MartinP
    I've used boost::gregorian::date a bit now. I can see that there are the related months & years & weeks duration types. I can see how to use known durations to advance a given date. Qu: But how can I get the difference between two dates in months (or years or weeks) ? I was hoping to find a function like: template<typename DURATION> DURATION date_diff<DURATION>(const date& d1,const date& d2); There would need to be some handling of rounding too.

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  • Is calling of overload operator-> resolved at compile time?

    - by Brent
    when I tried to compile the code: (note: func and func2 is not typo) struct S { void func2() {} }; class O { public: inline S* operator->() const; private: S* ses; }; inline S* O::operator->() const { return ses; } int main() { O object; object->func(); return 0; } there is a compile error reported: D:\code>g++ operatorp.cpp -S -o operatorp.exe operatorp.cpp: In function `int main()': operatorp.cpp:27: error: 'struct S' has no member named 'func' it seems that invoke the overloaded function of "operator-" is done during compile time? I'd added "-S" option for compile only.

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  • How to free memory in try-catch blocks?

    - by Kra
    Hi, I have a simple question hopefully - how does one free memory which was allocated in the try block when the exception occurs? Consider the following code: try { char *heap = new char [50]; //let exception occur here delete[] heap; } catch (...) { cout << "Error, leaving function now"; //delete[] heap; doesn't work of course, heap is unknown to compiler return 1; } How can I free memory after the heap was allocated and exception occurred before calling delete[] heap? Is there a rule not to allocate memory on heap in these try .. catch blocks? Thanks

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  • Sorting array of structs

    - by mrblippy
    Hi, i am having trouble making a method to sort an array of structs. i am tring to sort them in ascending order based on classcode. any help you could give would be appreciated struct unit { char classcode[4]; char *classname; }; void insertion_sort(struct unit u[], int n) { int j, p; struct unit tmp[1]; for(p = 1; p < n; p++) { tmp[0] = u[p]; for(j = p; j > 0 && (strcmp(tmp[j-1].classcode, tmp[p].classcode) > 0); j--) u[j] = u[j-1]; u[j] = tmp[0]; } }

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  • inline and member initializers

    - by Alexander
    When should I inline a member function and when should I use member initializers? My code is below.. I would like to modify it so I could make use some inline when appropriate and member initializers: #include "Books.h" Book::Book(){ nm = (char*)""; thck = 0; wght = 0; } Book::Book(const char *name, int thickness, int weight){ nm = strdup(name); thck = thickness; wght = weight; } Book::~Book(){ } const char* Book::name(){ return nm; } int Book::thickness(){ return thck; } int Book::weight(){ return wght; } // // Prints information about the book using this format: // "%s (%d mm, %d dg)\n" // void Book::print(){ printf("%s (%d mm, %d dg)\n", nm, thck, wght); } Bookcase::Bookcase(int id){ my_id = id; no_shelf = 0; } int Bookcase::id(){ return my_id; } Bookcase::~Bookcase(){ for (int i = 0; i < no_shelf; i++) delete my_shelf[i]; } bool Bookcase::addShelf(int width, int capacity){ if(no_shelf == 10) return false; else{ my_shelf[no_shelf] = new Shelf(width, capacity); no_shelf++; return true; } } bool Bookcase::add(Book *bp){ int index = -1; int temp_space = -1; for (int i = 0; i < no_shelf; i++){ if (bp->weight() + my_shelf[i]->curCapacity() <= my_shelf[i]->capacity()){ if (bp->thickness() + my_shelf[i]->curWidth() <= my_shelf[i]->width() && temp_space < (my_shelf[i]->width() - my_shelf[i]->curWidth())){ temp_space = (my_shelf[i]->width()- my_shelf[i]->curWidth()); index = i; } } } if (index != -1){ my_shelf[index]->add(bp); return true; }else return false; } void Bookcase::print(){ printf("Bookcase #%d\n", my_id); for (int i = 0; i < no_shelf; i++){ printf("--- Shelf (%d mm, %d dg) ---\n", my_shelf[i]->width(), my_shelf[i]->capacity()); my_shelf[i]->print(); } }

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  • Dynamic allocated array is not freed

    - by Stefano
    I'm using the code above to dynamically allocate an array, do some work inside the function, return an element of the array and free the memory outside of the function. But when I try to deallocate the array it doesn't free the memory and I have a memory leak. The debugger pointed to the myArray variable shows me the error CXX0030. Why? struct MYSTRUCT { char *myvariable1; int myvariable2; char *myvariable2; .... }; void MyClass::MyFunction1() { MYSTRUCT *myArray= NULL; MYSTRUCT *myElement = this->MyFunction2(myArray); ... delete [] myArray; } MYSTRUCT* MyClass::MyFunction2(MYSTRUCT *array) { array = (MYSTRUCT*)operator new(bytesLength); ... return array[X]; }

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  • Legality Of Re-Implementing An Existing API (e.g. GNU implementing the UNIX APIs)

    - by splicer
    I've often wondered about this. I'm not looking for legal advice, just casual opinions ;) If some company publishes an API on the web for their closed-source library, would it be legal for another party to release an open-source implementation of that API? Are function declarations considered source code? Take GNU implementing the UNIX APIs, for example. The UNIX standard gives the following function declaration and defines its required behaviour in English: char * mktemp(char *template); Now, consider an API that lists and declares and describes several thousand (more much complex) functions, enums, etc.; an API which defines a solution to a non-trival set of problems. If an open-source project publishes C headers that copy (verbatim) the function definitions contained in the closed-source company's published API, doesn't that violate some sort copyright law?

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  • Perfect Forwarding to async lambda

    - by Alexander Kondratskiy
    I have a function template, where I want to do perfect forwarding into a lambda that I run on another thread. Here is a minimal test case which you can directly compile: #include <thread> #include <future> #include <utility> #include <iostream> #include <vector> /** * Function template that does perfect forwarding to a lambda inside an * async call (or at least tries to). I want both instantiations of the * function to work (one for lvalue references T&, and rvalue reference T&&). * However, I cannot get the code to compile when calling it with an lvalue. * See main() below. */ template <typename T> std::string accessValueAsync(T&& obj) { std::future<std::string> fut = std::async(std::launch::async, [](T&& vec) mutable { return vec[0]; }, std::forward<T>(obj)); return fut.get(); } int main(int argc, char const *argv[]) { std::vector<std::string> lvalue{"Testing"}; // calling with what I assume is an lvalue reference does NOT compile std::cout << accessValueAsync(lvalue) << std::endl; // calling with rvalue reference compiles std::cout << accessValueAsync(std::move(lvalue)) << std::endl; // I want both to compile. return 0; } For the non-compiling case, here is the last line of the error message which is intelligible: main.cpp|13 col 29| note: no known conversion for argument 1 from ‘std::vector<std::basic_string<char> >’ to ‘std::vector<std::basic_string<char> >&’ I have a feeling it may have something to do with how T&& is deduced, but I can't pinpoint the exact point of failure and fix it. Any suggestions? Thank you! EDIT: I am using gcc 4.7.0 just in case this could be a compiler issue (probably not)

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