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  • c++ casting base class to derived class mess

    - by alan2here
    If I were to create a base class called base and derived classes called derived_1, derived_2 etc... I use a collection of instances of the base class, then when I retrieved an element and tried to use it I would find that C++ thinks it's type is that of the base class, probably because I retrieved it from a std::vector of base. Which is a problem when I want to use features that only exist for the specific derived class who's type I knew this object was when I put it into the vector. So I cast the element into the type it is supposed to be and found this wouldn't work. (derived_3)obj_to_be_fixed; And remembered that it's a pointer thing. After some tweaking this now worked. *((derived_3*)&obj_to_be_fixed); Is this right or is there for example an abc_cast() function that does it with less mess?

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  • What is the difference between Multiple R-squared and Adjusted R-squared in a single-variate least s

    - by fmark
    Could someone explain to the statistically naive what the difference between Multiple R-squared and Adjusted R-squared is? I am doing a single-variate regression analysis as follows: v.lm <- lm(epm ~ n_days, data=v) print(summary(v.lm)) Results: Call: lm(formula = epm ~ n_days, data = v) Residuals: Min 1Q Median 3Q Max -693.59 -325.79 53.34 302.46 964.95 Coefficients: Estimate Std. Error t value Pr(>|t|) (Intercept) 2550.39 92.15 27.677 <2e-16 *** n_days -13.12 5.39 -2.433 0.0216 * --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Residual standard error: 410.1 on 28 degrees of freedom Multiple R-squared: 0.1746, Adjusted R-squared: 0.1451 F-statistic: 5.921 on 1 and 28 DF, p-value: 0.0216 Apologies for the newbiness of this question.

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  • C++ stack memory still valid?

    - by jbu
    Hi all, If I create an object on the stack and push it into a list, then the object loses scope (outside of the for loop in the example below) will the object still exist in the list? If the list still holds the object, is that data now invalid/possibly corrupt? Please let me know, and please explain the reasoning.. Thanks, jbu class SomeObject{ public: AnotherObject x; } //And then... void someMethod() { std::list<SomeObject> my_list; for(int i = 0; i < SOME_NUMBER; i++) { SomeObject tmp; my_list.push_back(tmp); //after the for loop iteration, tmp loses scope } my_list.front(); //at this point will my_list be full of valid SomeObjects or will the SomeObjects no longer be valid, even if they still point to dirty data }

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  • C++ porting templates to Red hat enterprise linux version 5

    - by mkal
    #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> template <class OutType> bool getVAL(OutType &value_out, const std::string &key) { return false; } int main (int argc, char*argv[]) { mode_t a; getVAL(a, "abc"); } test.cpp:6: error: ISO C++ forbids declaration of ‘parameter’ with no type test.cpp: In function ‘int main(int, char**)’: test.cpp:13: error: no matching function for call to ‘getVAL(mode_t&, const char [4])’

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  • Is it a good idea to create an STL iterator which is noncopyable?

    - by BillyONeal
    Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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  • C++ Ambiguous call to Overloaded Function (const variety)

    - by Joe
    After researching this online, I've only found solutions that don't apply to my problem, so please bear with me. Code snippet: typedef my_map_t<int const *, float> _test; my_map_t::const_iterator not_found = my_map_t::end(); if (_test.find(&iKeyValue) == not_found) { _test[iKeyValue] = 4 + 5; // not the actual code, but here for simplicity } The compiler complains that there's an ambiguous call to my_map_t::end(). This makes sense, because the only difference is the return type. Output: error C2668: 'std::_Tree<_Traits>::end' : ambiguous call to overloaded function Normally you can disambiguate the call by casting the parameters, but end() has no parameters. Any ideas?

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  • Escape characters during paste in vim

    - by Michael Anderson
    I copy stuff from output buffers into C++ code I'm working on in vim. Often this output gets stuck into strings. And it'd be nice to be able to escape all the control characters automatically rather than going back and hand editing the pasted fragment. As an example I might copy something like this: error in file "foo.dat" And need to put it into something like this std::string expected_error = "error in file \"foo.dat\"" I'm thinking it might be possible to apply a replace function to the body of the last paste using the start and end marks of the last paste, but I'm not sure how to make it fly.

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  • C++ string array binary search

    - by Jose Vega
    string Haystack[] = { "Alabama", "Alaska", "American Samoa", "Arizona", "Arkansas", "California", "Colorado", "Connecticut", "Delaware", "District of Columbia", "Florida", "Georgia", "Guam", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas", "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts", "Michigan", "Minnesota", "Mississippi", "Missouri", "Montana", "Nebraska", "Nevada", "New Hampshire", "New Jersey", "New Mexico", "New York", "North Carolina", "North Dakota", "Northern Mariana Islands", "Ohio", "Oklahoma", "Oregon", "Pennsylvania", "Puerto Rico", "Rhode Island", "South Carolina", "South Dakota", "Tennessee", "Texas", "US Virgin Islands", "Utah", "Vermont", "Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming"}; string Needle = "Virginia"; if(std::binary_search(Haystack, Haystack+56, Needle)) cout<<"Found"; If I also wanted to find the location of the needle in the string array, is there an "easy" way to find out?

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  • how to specify set of files to be copied in lib while creating war

    - by Jigar Shah
    This is my build target <target name="build-war" depends="build-java"> <war destfile="${dist.dir}/${std.war.file}" webxml="${resources.dir}/WEB-INF/web.xml"> <fileset dir="${jsp.dir}" /> <lib dir="${lib.dir}"/> <classes dir="${build.classes.dir}" /> </war> </target> Here for <lib> can i specify some how a fileset / pattern set ? Basically i want to copy different jar from different places. (Not in one directlry) And That fileset or patternset i want to be defined in another build file which actually imports this build file. <lib refid="${patternset.id}"/>

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  • Cannot find sleep function

    - by Tyzak
    hello, i'm new at C Programming (i learned c++) i want to create a process with windows.h at first i just want to start my main programm that creates a process ( -- starts an other programm) that's my code, but it doesn't really work, i removed every unnessasery line of code but "void sleep(700)" (or "sleep (700)" for testing if the windows methods work, but i get an error, that "sleep" cant be found. #include <iostream> #include <windows.h> #include <string> using namespace std; void main() { //bool ret; //startupinfo stupinfo; //prozess_information pro2info; //Getstartupinfo (&stupinfo); //createprozess(null, "C:\\bsss10\\betriebssystemePRA1.exe", null, null, false, create_new_console, null, // null, &stupinfo, &pro2info); sleep (700); cout<< "hello"; } thanks in advance

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  • Problem with operator ==

    - by CPPDev
    I am facing some problem with use of operator == in the following c++ program. #include < iostream> using namespace std; class A { public: A(char *b) { a = b; } A(A &c) { a = c.a; } bool operator ==(A &other) { return strcmp(a, other.a); } private: char *a; }; int main() { A obj("test"); A obj1("test1"); if(obj1 == A("test1")) { cout<<"This is true"<<endl; } } What's wrong with if(obj1 == A("test1")) line ?? Any help is appreciated.

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  • Can I use Visual Studio 2010's compiler with Visual Studio 2008's Runtime Library?

    - by BillyONeal
    Hello everyone :) I have an application that needs to operate on Windows 2000. I'd also like to use Visual Studio 2010 (mainly because of the change in the definition of the auto keyword). However, I'm in a bit of a bind because I need the app to be able to operate on older OS's, namely: Windows 2000 Windows XP RTM Windows XP SP1 Visual Studio 2010's runtime library depends on the EncodePointer / DecodePointer API which was introduced in Windows XP SP2. If using the alternate runtime library is possible, will this break code that relies on C++0x features added in VS2010, like std::regex?

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  • What does: throw 0 do/mean? Is it "bad"?

    - by MartinP
    Context I came across some code, like this: if( Some_Condition ) throw 0; I googled a bit, and found a few other code snippets using that odd looking throw 0 form. I presume one would catch this as: catch(const int& e) { } Or is this a NULL ptr? to be caught as void* ? Question What does this throw 0 do? Is it special in some way? My normal preference would be to throw something that is (or derived from) std::exception. So to me this looks "bad". Is it "bad" ?

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  • How *restrict / *__restrict__ works in C / C++?

    - by Moraru Lilian
    Here is some code I wrote: #include <iostream> using namespace std; int main(void) { int i = 7; int *__restrict__ a = &i; *a = 5; int *b = &i, *c = &i; *b = 8; *c = 9; cout << **&a << endl; //*a return 0; } From what I've read, if I do " *a = 5 ", it changes the value of the memory he, "a", is pointing to, after that the memory to which he is pointing to should not be modified by anyone else except "a", which means that these program is wrong because "b" and "c" modify it after that. Or, even if "b" modifies "i" first, after that only "a" should have access to that memory( "i" ). Am I getting it correctly?

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  • How to convert an existing callback interface to use boost signals & slots

    - by the_mandrill
    I've currently got a class that can notify a number of other objects via callbacks: class Callback { virtual NodulesChanged() =0; virtual TurkiesTwisted() =0; }; class Notifier { std::vector<Callback*> m_Callbacks; void AddCallback(Callback* cb) {m_Callbacks.push(cb); } ... void ChangeNodules() { for (iterator it=m_Callbacks.begin(); it!=m_Callbacks.end(); it++) { (*it)->NodulesChanged(); } } }; I'm considering changing this to use boost's signals and slots as it would be beneficial to reduce the likelihood of dangling pointers when the callee gets deleted, among other things. However, as it stands boost's signals seems more oriented towards dealing with function objects. What would be the best way of adapting my code to still use the callback interface but use signals and slots to deal with the connection and notification aspects?

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  • Simple vector program error

    - by Codeguru
    Hi iam new to c++ and iam trying out this vector program and i am getting the following error: error: conversion from test*' to non-scalar typetest' requested| Here is the code include include include include using namespace std; class test{ string s; vector <string> v; public: void read(){ ifstream in ("c://test.txt"); while(getline(in,s)) { v.push_back(s); } for(int i=0;i<v.size();i++) { cout<<v[i]<<"\n"; } } }; int main() { cout<<"Opening the file to read and displaying on the screen"< }

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  • C++: ifstream::getline problem

    - by Jay
    I am reading a file like this: char string[256]; std::ifstream file( "file.txt" ); // open the level file. if ( ! file ) // check if the file loaded fine. { // error } while ( file.getline( string, 256, ' ' ) ) { // handle input } Just for testing purposes, my file is just one line, with a space at the end: 12345 My code first reads the 12345 successfully. But then instead of the loop ending, it reads another string, which seems to be a return/newline. I have saved my file both in gedit and in nano. And I have also outputted it with the Linux cat command, and there is no return on the end. So the file should be fine. Why is my code reading a return/newline? Thanks.

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  • Unsigned long with negative value

    - by egiakoum1984
    Please see the simple code below: #include <iostream> #include <stdlib.h> using namespace std; int main(void) { unsigned long currentTrafficTypeValueDec; long input; input=63; currentTrafficTypeValueDec = (unsigned long) 1LL << input; cout << currentTrafficTypeValueDec << endl; printf("%u \n", currentTrafficTypeValueDec); printf("%ld \n", currentTrafficTypeValueDec); return 0; } Why printf() displays the currentTrafficTypeValueDec (unsigned long) with negative value? The output is: 9223372036854775808 0 -9223372036854775808

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  • Using stack defined in C++ stl

    - by cambr
    #include <stack> using namespace std; int main() { stack<int> s; int i; for (i = 0; i <= 10; i++) { s.push(i); } for (i = 0; i <= 10; i++) { printf("%d", s.pop()); } } Whats wrong with the code above? Error: In function `int main()': aggregate value used where an integer was expected

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  • STL Vectors, pointers and classes

    - by anubis9
    Hey! Let's say i have 2 classes: class Class1 { public: std::vector<CustomClass3*> mVec; public: Class1(); ~Class1() { //iterate over all the members of the vector and delete the objects } }; class InitializerClass2 { private: Class1 * mPtrToClass1; public: InitializerClass2(); void Initialize() { mPtrToClass1->mVec.push_back(new CustomClass3(bla bla parameters)); } }; Will this work? Or the memory allocated in the InitializerClass2::Initialize() method might get corrupted after the method terminates? Thanks!

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  • Are large include files like iostream efficient? (C++)

    - by Keand64
    Iostream, when all of the files it includes, the files that those include, and so on and so forth, adds up to about 3000 lines. Consider the hello world program, which needs no more functionality than to print something to the screen: #include <iostream> //+3000 lines right there. int main() { std::cout << "Hello, World!"; return 0; } this should be a very simple piece of code, but iostream adds 3000+ lines to a marginal piece of code. So, are these 3000+ lines of code really needed to simply display a single line to the screen, and if not, do they create a less efficient program than if I simply copied the relevant lines into the code?

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  • clearing cin input? cin.ignore not a good way?

    - by igor
    What's a better way to clear cin input? I thought cin.clear and cin.ignore was a good way...? code: void clearInput() { cin.clear(); cin.ignore(1000,'\n'); //cin.ignore( std::numeric_limits<streamsize>::max(), '\n' ); } My teacher gave me this reply... this is basically saying that your clearInput doesn't work FYI: ignore is NEVER a good idea as a way of getting rid of all that remains on a line and your failing this test is exactly the reason why now go clear it the correct way

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  • Strange fstream problem

    - by noname
    Hi, I have really strange problem. In Visual C++ express, I have very simple code, just: #include <fstream> using namespace std; int main() { fstream file; file.open("test.txt"); file<<"Hello"; file.close(); } This same code works OK in my one project, but when I create now project and use this same lines of code, no file test.txt is created. Please, what is wrong?¨ EDIT: I expect to see test.txt in VS2008/project_name/debug - just like the first functional project does.

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  • Inheriting and static members

    - by Bruce
    Here is my code - #include <iostream> #include <conio.h> using namespace std; class Base { public: int a; }; //int Base::a = 5; class Derived : public Base { public: int static a; }; int main() { Derived d; cout<<d.a; getch(); return 0; } I get a linker error here. But when I do it the other way round - class Base { public: int static a; }; int Base::a = 5; class Derived : public Base { public: int a; }; I get no error. Can someone please explain what is happening here.

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