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  • Python extension building with boost

    - by user1544053
    Hey guys I'm fairly new to boost c/c++ library. I downloaded boost library and build the library. I created a very simple python library in c++ using boost interface (actually it is example code given in the documentation). I built it into a dll file. In the documentation it reads that this dll is exposed to python and they just show the import function in python and include the created library. I don't understand how to expose that dll to python and load the library inside in tradition ('import') manner. In case if you wanna look at the code then here it is: #include <boost/python.hpp> char const* greet() { return "hello, world"; } BOOST_PYTHON_MODULE(hello_ext) { using namespace boost::python; def("greet", greet); } Please help I really want to build applications with c/c++ and python. I simply want to use hello_ext as: >>>import hello_ext >>>print hello_ext.greet() Thank you.

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  • How to use SOCI C++ Database library?

    - by NeDark
    I'm trying to implement soci in my program but I don't know how. I'm using C++ on linux, on a project on netbeans. I have followed the steps in http://soci.sourceforge.net/doc/structure.html to install it, and I tried to copy the files soci.h from /src/core and soci-mysql.h from /src/backends/mysql in my proyect but it gives compilation error (these files include other soci files, but it's illogical to copy all files into the directory...). I have read the guide several time but I don't understand what I'm doing wrong, the examples only include these files. Thanks. Edit: I have given more information in a comment below the answer. I don't know what steps I have to do to implement soci.

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  • C++ - defining static const integer members in class definition

    - by HighCommander4
    My understanding is that C++ allows static const members to be defined inside a class so long as it's an integer type. Why, then, does the following code give me a linker error? #include <algorithm> #include <iostream> class test { public: static const int N = 10; }; int main() { std::cout << test::N << "\n"; std::min(9, test::N); } The error I get is: test.cpp:(.text+0x130): undefined reference to `test::N' collect2: ld returned 1 exit status Interestingly, if I comment out the call to std::min, the code compiles and links just fine (even though test::N is also referenced on the previous line). Any idea as to what's going on? My compiler is gcc 4.4 on Linux.

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  • Partial coverage of a return statement in C++/CLI

    - by brickner
    I have C++/CLI code and I'm using Visual Studio 2008 Team Suite Code Coverage. The code header: // Library.h #pragma once #include <string> using namespace System; namespace Library { public ref class MyClass { public: static void MyFoo(); static std::string Foo(); }; } The code implementation: #include "Library.h" using namespace Library; using namespace System; void MyClass::MyFoo() { Foo(); } std::string MyClass::Foo() { return std::string(); } I have a C# unit test, that calls MyClass.MyFoo(): [TestMethod] public void TestMethod1() { Library.MyClass.MyFoo(); } For some reason, I don't get a full code coverage for MyClass. The Foo() method has 3 uncovered blocks and 5 covered blocks. The closing curly brackets (}) are marked in orange - partially covered. I have no idea why is it partially covered instead of fully covered, and this is my question.

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  • How Iostream file is located in computer by c++ code during execution

    - by user3702024
    i want to know that in a c++ code during execution how iostream file is founded. we write #include in c++ program and i know about #include which is a preprocessor directive to load files and is a file name but i don't know that how that file is located. i have some questions in my mind... Is Standard library present in compiler which we are using? Is that file is present in standard library or in our computer? Can we give directory path to locate the file through c++ code if yes then how?

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  • Can't access variables from dynamically loaded javascript

    - by Menno
    I'm using a fairly simple system to load javascript dynamically: include = function (url) { var e = document.createElement("script"); e.src = url; e.type="text/javascript"; document.getElementsByTagName("head")[0].appendChild(e); }; Let's say I have a file test.js which has the following contents: var foo = 4; Now, in my original script, I want to use include(test.js); console.log(foo); However, I get a 'foo has not been defined' error on this. I'm guessing it has to do with the dynamic script being included as the last child of the <head> tag. How can I get this to work?

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  • Does this have anything to do with endian-ness?

    - by eSKay
    This piece of code: #include<stdio.h> void hello() { printf("hello\n"); } void bye() { printf("bye\n"); } int main() { printf("%p\n", hello); printf("%p\n", bye); return 0; } output on my machine: 0x80483f4 0x8048408 [second address is bigger in value] on Codepad 0x8048541 0x8048511 [second address is smaller in value] Does this have anything to do with endian-ness of the machines? If not, Why the difference in the ordering of the addresses? Also, Why the difference in the difference? 0x8048541 - 0x8048511 = 0x30 0x8048408 - 0x80483f4 = 0x14 Btw, I just checked. This code (taken from here) says that both the machines are Little-Endian #include<stdio.h> int main() { int num = 1; if(*(char *)&num == 1) printf("Little-Endian\n"); else printf("Big-Endian\n"); return 0; }

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  • MiniDumpWriteDump segfault?

    - by Steven Penny
    I am trying to dump a process, say calc.exe When I run my program I get Program received signal SIGSEGV, Segmentation fault. 0x0000000000401640 in MiniDumpWriteDump () Here is the code #include <windows.h> #include <dbghelp.h> int main(){ HANDLE hFile = CreateFileA( "calc.dmp", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_DELETE | FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL ); DWORD procID = 196; HANDLE hProc = OpenProcess( PROCESS_ALL_ACCESS, FALSE, procID ); MiniDumpWriteDump( hProc, procID, hFile, MiniDumpNormal, NULL, NULL, NULL ); CloseHandle(hFile); }

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  • C++ vector pointer/reference problem

    - by sub
    Please take a look at this example: #include <iostream> #include <vector> #include <string> using namespace std; class mySubContainer { public: string val; }; class myMainContainer { public: mySubContainer sub; }; void doSomethingWith( myMainContainer &container ) { container.sub.val = "I was modified"; } int main( ) { vector<myMainContainer> vec; /** * Add test data */ myMainContainer tempInst; tempInst.sub.val = "foo"; vec.push_back( tempInst ); tempInst.sub.val = "bar"; vec.push_back( tempInst ); // 1000 lines of random code here int i; int size = vec.size( ); myMainContainer current; for( i = 0; i < size; i ++ ) { cout << i << ": Value before='" << vec.at( i ).sub.val << "'" << endl; current = vec.at( i ); doSomethingWith( current ); cout << i << ": Value after='" << vec.at( i ).sub.val << "'" << endl; } system("pause");//i suck } A hell lot of code for an example, I know. Now so you don't have to spend years thinking about what this [should] do[es]: I have a class myMainContainer which has as its only member an instance of mySubContainer. mySubContainer only has a string val as member. So I create a vector and fill it with some sample data. Now, what I want to do is: Iterate through the vector and make a separate function able to modify the current myMainContainer in the vector. However, the vector remains unchanged as the output tells: 0: Value before='foo' 0: Value after='foo' 1: Value before='bar' 1: Value after='bar' What am I doing wrong? doSomethingWith has to return void, I can't let it return the modified myMainContainer and then just overwrite it in the vector, that's why I tried to pass it by reference as seen in the doSomethingWith definition above.

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  • Should we use temporary variables for the returned values of functions?

    - by totymedli
    I thought about this: Is there a performance difference in these two practices: Store the return value of a function in a temporary variable than give that variable as a parameter to another function. Put the function into the other function. Specification Assuming all classes and functions are written correctly. Case 1. ClassA a = function1(); ClassB b = function2(a); function3(b); Case 2. function3(function2(function1())); I know there aren't a big difference with only one run, but supposed that we could run this a lot of times in a loop, I created some tests. Test #include <iostream> #include <ctime> #include <math.h> using namespace std; int main() { clock_t start = clock(); clock_t ends = clock(); // Case 1. start = clock(); for (int i=0; i<10000000; i++) { double a = cos(1); double b = pow(a, 2); sqrt(b); } ends = clock(); cout << (double) (ends - start) / CLOCKS_PER_SEC << endl; // Case 2. start = clock(); for (int i=0; i<10000000; i++) sqrt(pow(cos(1),2)); ends = clock(); cout << (double) (ends - start) / CLOCKS_PER_SEC << endl; return 0; } Results Case 1 = 6.375 Case 2 = 0.031 Why is the first one is much slower, and if the second one is faster why dont we always write code that way? Anyway does the second pratice has a name? I also wondered what happens if I create the variables outside the for loop in the first case, but the result was the same. Why?

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  • Why this C program outputs a negative number?

    - by JMSA
    I have assigned the complement value in an unsigned variable. Then why this C program outputs a negative number? #include<stdio.h> #include<conio.h> int main() { unsigned int Value = 4; /* 4 = 0000 0000 0000 0100 */ unsigned int result = 0; result = ~ Value; /* -5 = 1111 1111 1111 1011 */ printf("result = %d", result); /* -5 */ getch(); return 0; }

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  • how to compile youtube-api appliation

    - by Gpathy
    Hi, i am developing a custom Youtube video player. But i am not able to compile the program. I am missing something in Makefile. My program looks like main.c #include<gdata/services/youtube/gdata-youtube-service.h> int main(int argc, char **argv[]) { printf("Youtube Application\n"); return 0; } makefile gcc `pkg-config --cflags --libs libgdata-google-1.2`  -lgdata-google-1.2 main.c -o youtube When i compile, it is giving error like error: gdata/services/youtube/gdata-youtube-service.h: No such file or directory Do i got to install some other packages ? Or, i need to include something in my Makefile ? Thanks...

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  • How can I change ruby log level in unit tests based on context

    - by Stuart
    I'm new to ruby so forgive me if this is simple or I get some terminology wrong. I've got a bunch of unit tests (actually they're integration tests for another project, but they use ruby test/unit) and they all include from a module that sets up an instance variable for the log object. When I run the individual tests I'd like log.level to be debug, but when I run a suite I'd like log.level to be error. Is it possible to do this with the approach I'm taking, or does the code need to be restructured? Here's a small example of what I have so far. The logging module: #!/usr/bin/env ruby require 'logger' module MyLog def setup @log = Logger.new(STDOUT) @log.level = Logger::DEBUG end end A test: #!/usr/bin/env ruby require 'test/unit' require 'mylog' class Test1 < Test::Unit::TestCase include MyLog def test_something @log.info("About to test something") # Test goes here @log.info("Done testing something") end end A test suite made up of all the tests in its directory: #!/usr/bin/env ruby Dir.foreach(".") do |path| if /it-.*\.rb/.match(File.basename(path)) require path end end

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  • installing widgets for qt

    - by Lakshan Perera
    I resently found a very useful set of widgets set for qt from http://www.wysota.eu.org/wwwidgets/ and I downloaded wwWidgets 1.0 installer for MinGW and simply installed it. now I can see those widgets in qt creator, and I can drag and drop them. but when compiling the project it says that those include files are not found. (ex: qwwled.h not found) but I see that file is in C:\Qt\4.8.3\include\wwWidgets please if someone can help me in this issue I would be very thankful. im using qt 4.8.3 with mingw 4.4

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  • how to avoid temporaries when copying weakly typed object

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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  • Including full LaTeX documents within others.

    - by Chris Clarke
    I'm currently finishing off my dissertation, and would like to be able to include some documents within my LaTeX document. The files I'd like to include are weekly reports done in LaTeX to my supervisor. Obviously all documents are page numbered seperately. I would like them to be included in the final document. I could concatenate all the final PDFs using GhostScript or some other tool, but I would like to have consistent numbering throughout the document. I have tried including the LaTeX from each document in the main document, but the preamble etc causes problems and the small title I have in each report takes a whole page... In summary, I'm looking for a way of including a number of 1 or 2 page self-complete LaTeX files in a large report, keeping their original layouts, but changing the page numbering.

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  • C Struct : typedef Doubt !

    - by Mahesh
    In the given code snippet, I expected the error symbol Record not found. But it compiled and ran fine on Visual Studio 2010 Compiler. I ran it as a C program from Visual Studio 2010 Command Prompt in the manner - cl Record.c Record Now the doubt is, doesn't typedef check for symbols ? Does it work more like a forward declaration ? #include "stdio.h" #include "conio.h" typedef struct Record R; struct Record { int a; }; int main() { R obj = {10}; getch(); return 0; }

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  • c++: how can i read a file line by line to a string type variable?

    - by ufk
    Hiya. I'm trying to read a file line by line to a string type variable using the following code: #include <iostream> #include <fstream> ifstream file(file_name); if (!file) { cout << "unable to open file"; exit(1); } string line; while (!file.eof()) { file.getline(line,256); cout<<line; } file.close(); it won't compile when I try to use String class, only when i use char file[256] instead. how can I get line by line into a string class? thanks!

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  • Function argument treated as undeclared

    - by Mikulas Dite
    I've prepared this simple example which is not working for me #include <stdio.h> #include <stdlib.h> FILE *fp; char filename[] = "damy.txt"; void echo (char[] text) { fp = fopen(filename, "a"); fwrite(text, 1, strlen(text), fp); fclose(fp); printf(text); } int main () { echo("foo bar"); return 0; } It's supposed to write both to command window and to file. However, this gives compilation error - the text used in echo() is not declared. Does c need another declaration of the variable?

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  • where to put business logic in a library?

    - by fayer
    i'm going to create a library that consists of a lot of separate classes. i'm very familiar with mvc but have never created a pure library before. i wonder where i should put the business logic? the logic that is in the controller in a mvc. should it be in a class? or in a "bootstrap" file? and should one file include every class, or should only one class include its classes it uses? thanks!

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  • Storing objects in STL vector - minimal set of methods

    - by osgx
    Hello What is "minimal framework" (necessary methods) of object, which I will store in STL <vector>? For my assumptions: #include <vector> #include <cstring> using namespace std; class Doit { private: char *a; public: Doit(){a=(char*)malloc(10);} ~Doit(){free(a);} }; int main(){ vector<Doit> v(10); } gives *** glibc detected *** ./a.out: double free or corruption (fasttop): 0x0804b008 *** Aborted and in valgrind: malloc/free: 2 allocs, 12 frees, 50 bytes allocated.

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  • How can I declare classes that refer to each other?

    - by Without me Its just Aweso
    It's been a long time since I've done C++ and I'm running into some trouble with classes referencing each other. Right now I have something like: a.h class a { public: a(); bool skeletonfunc(b temp); }; b.h class b { public: b(); bool skeletonfunc(a temp); }; Since each one needs a reference to the other, I've found I can't do a #include of each other at the top or I end up in a weird loop of sorts with the includes. So how can I make it so that a can use b and vice versa without making a cyclical #include problem? thanks!

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  • Drop into read-eval-print loop from PHP code?

    - by Mickey
    Is there a way to drop into a read-eval-print loop from inside PHP code during execution, in a script that was run from the command line? That is, like php -a or phpsh? Or do I have to re-implement a REPL from scratch? I can't find any way to do it. To clarify: the reason why I need to do this is that I want to automatically include all the files in my project once the REPL starts, instead of having to manually include everything by hand.

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  • which is time consuming construct in following program?

    - by user388338
    while submitting a solution for practise problem 6(odd) i got TLE error but while using using print and scanf in place cin and cout my sol was submitted successfully with 0.77s time..i want to know how can i make it more efficient link to problem is codechef problem 6 #include<iostream> #include<cstdio> using namespace std; int main() {int n,N; scanf("%d",&n); for(int l=0;l<n;l++) { scanf("%d",&N); int i=0,x; if(N<=0) continue; for(;N>=(x=(2<<i));i++); printf("%d",x/2); cout<<"\n"; } }

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