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  • Coordinating typedefs and structs in std::multiset (C++)

    - by Sarah
    I'm not a professional programmer, so please don't hesitate to state the obvious. My goal is to use a std::multiset container (typedef EventMultiSet) called currentEvents to organize a list of structs, of type Event, and to have members of class Host occasionally add new Event structs to currentEvents. The structs are supposed to be sorted by one of their members, time. I am not sure how much of what I am trying to do is legal; the g++ compiler reports (in "Host.h") "error: 'EventMultiSet' has not been declared." Here's what I'm doing: // Event.h struct Event { public: bool operator < ( const Event & rhs ) const { return ( time < rhs.time ); } double time; int eventID; int hostID; }; // Host.h ... void calcLifeHist( double, EventMultiSet * ); // produces compiler error ... void addEvent( double, int, int, EventMultiSet * ); // produces compiler error // Host.cpp #include "Event.h" ... // main.cpp #include "Event.h" ... typedef std::multiset< Event, std::less< Event > > EventMultiSet; EventMultiSet currentEvents; EventMultiSet * cePtr = &currentEvents; ... Major questions Where should I include the EventMultiSet typedef? Are my EventMultiSet pointers obviously problematic? Is the compare function within my Event struct (in theory) okay? Thank you very much in advance.

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  • bitly php url wont work???

    - by mathiregister
    Hi guys, <?php include('bitly.php'); $bitly = new bitly('myusername', 'myapikey'); print $bitly->shorten('http://www.google.com'); ?> WORKING!!! $currenturl = (!empty($_SERVER['HTTPS'])) ? "https://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'] : "http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']; include('bitly.php'); $bitly = new bitly('myusername', 'myapikey'); print $bitly->shorten($currenturl); WORKING!!! include('bitly.php'); $currenturl = (!empty($_SERVER['HTTPS'])) ? "https://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'] : "http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI']; $url = "somehashtag" $shareurl = $currenturl . '#' . $url; $bitly = new bitly('myusername', 'myapikey'); print $bitly->shorten($shareurl); NOT WORKING!!! Any idea why? If i print out the $shareurl i can see that it's a completely normal url that i could paste onto the normal bit.ly website. I don't get it! Any ideas? Would be great if you could help me!

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  • Splitting a C++ class into files now won't compile.

    - by vgm64
    Hi. I am teaching myself to write classes in C++ but can't seem to get the compilation to go through. If you can help me figure out not just how, but why, it would be greatly appreciated. Thank you in advance! Here are my three files: make_pmt.C #include <iostream> #include "pmt.h" using namespace std; int main() { CPMT *pmt = new CPMT; pmt->SetVoltage(900); pmt->SetGain(2e6); double voltage = pmt->GetVoltage(); double gain= pmt->GetGain(); cout << "The voltage is " << voltage << " and the gain is " << gain << "." <<endl; return 0; } pmt.C #include "pmt.h" using namespace std; class CPMT { double gain, voltage; public: double GetGain() {return gain;} double GetVoltage() {return voltage;} void SetGain(double g) {gain=g;} void SetVoltage(double v) {voltage=v;} }; pmt.h #ifndef PMT_H #define PMT_H 1 using namespace std; class CPMT { double gain, voltage; public: double GetGain(); double GetVoltage(); void SetGain(double g); void SetVoltage(double v); }; #endif And for reference, I get a linker error (right?): Undefined symbols: "CPMT::GetVoltage()", referenced from: _main in ccoYuMbH.o "CPMT::GetGain()", referenced from: _main in ccoYuMbH.o "CPMT::SetVoltage(double)", referenced from: _main in ccoYuMbH.o "CPMT::SetGain(double)", referenced from: _main in ccoYuMbH.o ld: symbol(s) not found collect2: ld returned 1 exit status

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  • Optimizing this "Boundarize" method for Numerics in Ruby

    - by mstksg
    I'm extending Numerics with a method I call "Boundarize" for lack of better name; I'm sure there are actually real names for this. But its basic purpose is to reset a given point to be within a boundary. That is, "wrapping" a point around the boundary; if the area is betweeon 0 and 100, if the point goes to -1, -1.boundarize(0,100) = 99 (going one too far to the negative "wraps" the point around to one from the max). 102.boundarize(0,100) = 2 It's a very simple function to implement; when the number is below the minimum, simply add (max-min) until it's in the boundary. If the number is above the maximum, simply subtract (max-min) until it's in the boundary. One thing I also need to account for is that, there are cases where I don't want to include the minimum in the range, and cases where I don't want to include the maximum in the range. This is specified as an argument. However, I fear that my current implementation is horribly, terribly, grossly inefficient. And because every time something moves on the screen, it has to re-run this, this is one of the bottlenecks of my application. Anyone have any ideas? module Boundarizer def boundarize min=0,max=1,allow_min=true,allow_max=false raise "Improper boundaries #{min}/#{max}" if min >= max new_num = self if allow_min while new_num < min new_num += (max-min) end else while new_num <= min new_num += (max-min) end end if allow_max while new_num > max new_num -= (max-min) end else while new_num >= max new_num -= (max-min) end end return new_num end end class Numeric include Boundarizer end

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  • are C functions declared in <c____> headers gauranteed to be in the global namespace as well as std?

    - by Evan Teran
    So this is something that I've always wondered but was never quite sure about. So it is strictly a matter of curiosity, not a real problem. As far as I understand, what you do something like #include <cstdlib> everything (except macros of course) are declared in the std:: namespace. Every implementation that I've ever seen does this by doing something like the following: #include <stdlib.h> namespace std { using ::abort; // etc.... } Which of course has the effect of things being in both the global namespace and std. Is this behavior guaranteed? Or is it possible that an implementation could put these things in std but not in the global namespace? The only way I can think of to do that would be to have your libstdc++ implement every c function itself placing them in std directly instead of just including the existing libc headers (because there is no mechanism to remove something from a namespace). Which is of course a lot of effort with little to no benefit. The essence of my question is, is the following program strictly conforming and guaranteed to work? #include <cstdio> int main() { ::printf("hello world\n"); }

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  • Path String Combination Question.

    - by Nano HE
    Hi. Please see my code below. ifstream myLibFile ("libs//%s" , line); // Compile failed here ??? I want to combine the path string and open the related file again. #include <iostream> #include <fstream> #include <string> using namespace std; int main () { string line; ifstream myfile ("libs//Config.txt"); // There are several file names listed in the COnfig.txt file line by line. if (myfile.is_open()) { while (! myfile.eof() ) { getline (myfile,line); cout << line << endl; // Read details lib files based on the each line file name. string libFileLine; ifstream myLibFile ("libs//%s" , line); // Compile failed here ??? if (myLibFile.is_open()) { while (! myLibFile.eof() ) { print "success"; } myLibFile.close(); } } myfile.close(); } else cout << "Unable to open file"; return 0; }

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  • C++ MACRO that will execute a block of code and a certain command after that block.

    - by Poni
    void main() { int xyz = 123; // original value { // code block starts xyz++; if(xyz < 1000) xyz = 1; } // code block ends int original_value = xyz; // should be 123 } void main() { int xyz = 123; // original value MACRO_NAME(xyz = 123) // the macro takes the code code that should be executed at the end of the block. { // code block starts xyz++; if(xyz < 1000) xyz = 1; } // code block ends << how to make the macro execute the "xyz = 123" statement? int original_value = xyz; // should be 123 } Only the first main() works. I think the comments explain the issue. It doesn't need to be a macro but to me it just sounds like a classical "macro-needed" case. By the way, there's the BOOST_FOREACH macro/library and I think it does the exact same thing I'm trying to achieve but it's too complex for me to find the essence of what I need. From its introductory manual page, an example: #include <string> #include <iostream> #include <boost/foreach.hpp> int main() { std::string hello( "Hello, world!" ); BOOST_FOREACH( char ch, hello ) { std::cout << ch; } return 0; }

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  • Cross-platform iteration of Unicode string

    - by kizzx2
    I want to iterate each character of a Unicode string, treating each surrogate pair and combining character sequence as a single unit (one grapheme). Example The text "??????" is comprised of the code points: U+0928, U+092E, U+0938, U+094D, U+0924, U+0947, of which, U+0938 and U+0947 are combining marks. static void Main(string[] args) { const string s = "??????"; Console.WriteLine(s.Length); // Ouptuts "6" var l = 0; var e = System.Globalization.StringInfo.GetTextElementEnumerator(s); while(e.MoveNext()) l++; Console.WriteLine(l); // Outputs "4" } So there we have it in .NET. We also have Win32's CharNextW() #include <Windows.h> #include <iostream> #include <string> int main() { const wchar_t * s = L"??????"; std::cout << std::wstring(s).length() << std::endl; // Gives "6" int l = 0; while(CharNextW(s) != s) { s = CharNextW(s); ++l; } std::cout << l << std::endl; // Gives "4" return 0; } Question Both ways I know of are specific to Microsoft. Are there portable ways to do it? I heard about ICU but I couldn't find something related quickly (UnicodeString(s).length() still gives 6). Would be an acceptable answer to point to the related function/module in ICU. C++ doesn't have a notion of Unicode, so a lightweight cross-platform library for dealing with these issues would make an acceptable answer.

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  • problem finding a header with a c++ makefile

    - by Max
    Hi. I've started working with my first makefile. I'm writing a roguelike in C++ using the libtcod library, and have the following hello world program to test if my environment's up and running: #include "libtcod.hpp" int main() { TCODConsole::initRoot(80, 50, "PartyHack"); TCODConsole::root->printCenter(40, 25, TCOD_BKGND_NONE, "Hello World"); TCODConsole::flush(); TCODConsole::waitForKeypress(true); } My project directory structure looks like this: /CppPartyHack ----/libtcod-1.5.1 # this is the libtcod root folder --------/include ------------libtcod.hpp ----/PartyHack --------makefile --------partyhack.cpp # the above code (while we're here, how do I do proper indentation? Using those dashes is silly.) and here's my makefile: SRCDIR = . INCDIR = ../libtcod-1.5.1/include CFLAGS = $(FLAGS) -I$(INCDIR) -I$(SRCDIR) -Wall CC = gcc CPP = g++ .SUFFIXES: .o .h .c .hpp .cpp $(TEMP)/%.o : $(SRCDIR)/%.cpp $(CPP) $(CFLAGS) -o $@ -c $< $(TEMP)/%.o : $(SRCDIR)/%.c $(CC) $(CFLAGS) -o $@ -c $< CPP_OBJS = $(TEMP)partyhack.o all : partyhack partyhack : $(CPP_OBJS) $(CPP) $(CPP_OBJS) -o $@ -L../libtcod-1.5.1 -ltcod -ltcod++ -Wl,-rpath,. clean : \rm -f $(CPP_OBJS) partyhack I'm using Ubuntu, and my terminal gives me the following errors: max@max-desktop:~/Desktop/Development/CppPartyhack/PartyHack$ make g++ -c -o partyhack.o partyhack.cpp partyhack.cpp:1:23: error: libtcod.hpp: No such file or directory partyhack.cpp: In function ‘int main()’: partyhack.cpp:5: error: ‘TCODConsole’ has not been declared partyhack.cpp:6: error: ‘TCODConsole’ has not been declared partyhack.cpp:6: error: ‘TCOD_BKGND_NONE’ was not declared in this scope partyhack.cpp:7: error: ‘TCODConsole’ has not been declared partyhack.cpp:8: error: ‘TCODConsole’ has not been declared make: * [partyhack.o] Error 1 So obviously, the makefile can't find libtcod.hpp. I've double checked and I'm sure the relative path to libtcod.hpp in INCDIR is correct, but as I'm just starting out with makefiles, I'm uncertain what else could be wrong. My makefile is based off a template that the libtcod designers provided along with the library itself, and while I've looked at a few online makefile tutorials, the code in this makefile is a good bit more complicated than any of the examples the tutorials showed, so I'm assuming I screwed up something basic in the conversion. Thanks for any help.

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  • FMOD Compiling trouble

    - by CptAJ
    I'm trying to get started with FMOD but I'm having some issues compiling the example code in this tutorial: http://www.gamedev.net/reference/articles/article2098.asp I'm using MinGW, I placed the libfmodex.a file in MinGW's include folder (I also tried linking directly to the filename) but it doesn't work. Here's the output. C:\>g++ -o test1.exe test1.cpp -lfmodex test1.cpp:4:1: error: 'FSOUND_SAMPLE' does not name a type test1.cpp: In function 'int main()': test1.cpp:9:29: error: 'FSOUND_Init' was not declared in this scope test1.cpp:12:4: error: 'handle' was not declared in this scope test1.cpp:12:53: error: 'FSOUND_Sample_Load' was not declared in this scope test1.cpp:13:30: error: 'FSOUND_PlaySound' was not declared in this scope test1.cpp:21:30: error: 'FSOUND_Sample_Free' was not declared in this scope test1.cpp:22:17: error: 'FSOUND_Close' was not declared in this scope This is the particular example I'm using: #include <conio.h> #include "inc/fmod.h" FSOUND_SAMPLE* handle; int main () { // init FMOD sound system FSOUND_Init (44100, 32, 0); // load and play sample handle=FSOUND_Sample_Load (0,"sample.mp3",0, 0, 0); FSOUND_PlaySound (0,handle); // wait until the users hits a key to end the app while (!_kbhit()) { } // clean up FSOUND_Sample_Free (handle); FSOUND_Close(); } I have the header files in the "inc" path where my code is. Any ideas as to what I'm doing wrong?

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  • Linking how PHP/HTML

    - by Azzyh
    Hello. Alright so im done doing pages with frames, and know i splitted up my design to top.php and bottom.php. In top.php it's linking to style.css and ajax_framework.js and such.. Now this works great until i tried to include top.php & bottom.php in videos/index.php (another dirr), i did like this: include "../top.php"; <-- and the originally index.php --> include "../bottom.php"; Now when i enter the site, it wont load style.css, probably because it thinks that style.css needs to be in videos/ directory, same goes with ajax_framework.js that are both files are on the parent ../ directory. Now what do i do? Some method or technique to solve this in a good way? So i dont have to copy style.css and ajax_framework.js into every directory i have, because then later if i want to change something i would need to change in all directories, which would be my last thing i want to do.. hope you got some nice techniques thank you

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  • CreateProcess() fails with an access violation

    - by John Doe
    My aim is to execute an external executable in my program. First, I used system() function, but I don't want the console to be seen to the user. So, I searched a bit, and found CreateProcess() function. However, when I try to pass a parameter to it, I don't know why, it fails. I took this code from MSDN, and changed a bit: #include <windows.h> #include <stdio.h> #include <tchar.h> void _tmain( int argc, TCHAR *argv[] ) { STARTUPINFO si; PROCESS_INFORMATION pi; ZeroMemory( &si, sizeof(si) ); si.cb = sizeof(si); ZeroMemory( &pi, sizeof(pi) ); /* if( argc != 2 ) { printf("Usage: %s [cmdline]\n", argv[0]); return; } */ // Start the child process. if( !CreateProcess( NULL, // No module name (use command line) L"c:\\users\\e\\desktop\\mspaint.exe", // Command line NULL, // Process handle not inheritable NULL, // Thread handle not inheritable FALSE, // Set handle inheritance to FALSE 0, // No creation flags NULL, // Use parent's environment block NULL, // Use parent's starting directory &si, // Pointer to STARTUPINFO structure &pi ) // Pointer to PROCESS_INFORMATION structure ) { printf( "CreateProcess failed (%d).\n", GetLastError() ); return; } // Wait until child process exits. WaitForSingleObject( pi.hProcess, INFINITE ); // Close process and thread handles. CloseHandle( pi.hProcess ); CloseHandle( pi.hThread ); } However, this code crated access violation somehow. Can I execute mspaint without showing user the console? Thank you very much.

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  • Is it a bug???????????????/

    - by Knowing me knowing you
    I'm using VS2010 Ultimate. Having code: //file IntSet.h #include "stdafx.h" #pragma once /*Class representing set of integers*/ template<class T> class IntSet { private: T** myData_; std::size_t mySize_; std::size_t myIndex_; public: #pragma region ctor/dtor explicit IntSet(); virtual ~IntSet(); #pragma endregion #pragma region publicInterface IntSet makeUnion(const IntSet&)const; IntSet makeIntersection(const IntSet&)const; IntSet makeSymmetricDifference(const IntSet&)const; void insert(const T&); #pragma endregion }; //file IntSet_impl.h #include "StdAfx.h" #include "IntSet.h" #pragma region ctor/dtor template<class T> IntSet<T>::IntSet():myData_(nullptr), mySize_(0), myIndex_(0) { } template<class T> IntSet<T>::~IntSet() { } #pragma endregion #pragma region publicInterface template<class T> void IntSet<T>::insert(const T& obj) {/*IF I SET A BREAKPOINT HERE AND AFTER THAT I CHANGE SOMETHING IN THE BODY I'M GETTING MSG SAYING THAT THE BREAKPOINT WILL NOT CURRENTLY BE HIT, AFTER I REBUILD THE BREAKPOINT IS VALID AGAIN*/ /*Check if we are initialized*/ if (mySize_ == 0) { mySize_ = 1; myData_ = new T*[mySize_]; } /*Check if we have place to insert obj in.*/ if (myIndex_ < mySize_) { myData_[myIndex_++] = new T(obj); return; } /*We didn't have enough place...*/ T** tmp = new T*[mySize_];//for copying old to temporary basket std::copy(&myData_[0],&myData_[mySize_],&tmp[0]); delete myData_; auto oldSize = mySize_; mySize_ *= 2; myData_ = new T*[mySize_]; std::copy(&tmp[0],&tmp[oldSize],&myData_[0]); myData_[myIndex_] = new T(obj); ++myIndex_; } #pragma endregion Thanks.

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  • Cannot overload function

    - by anio
    So I've got a templatized class and I want to overload the behavior of a function when I have specific type, say char. For all other types, let them do their own thing. However, c++ won't let me overload the function. Why can't I overload this function? I really really do not want to do template specialization, because then I've got duplicate the entire class. Here is a toy example demonstrating the problem: http://codepad.org/eTgLG932 The same code posted here for your reading pleasure: #include <iostream> #include <cstdlib> #include <string> struct Bar { std::string blah() { return "blah"; } }; template <typename T> struct Foo { public: std::string doX() { return m_getY(my_t); } private: std::string m_getY(char* p_msg) { return std::string(p_msg); } std::string m_getY(T* p_msg) { return p_msg->blah(); } T my_t; }; int main(int, char**) { Foo<char> x; Foo<Bar> y; std::cout << "x " << x.doX() << std::endl; return EXIT_SUCCESS; } Thank you everyone for your suggestions. Two valid solutions have been presented. I can either specialize the doX method, or specialize m_getY() method. At the end of the day I prefer to keep my specializations private rather than public so I'm accepting Krill's answer.

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  • c++ tables of unions and structures

    - by newbDeveloper
    I was told to write a program, that creates a union and structure, then creates two-element arrays of unions and structures and fills their fields. I have created a union and a structure, but how to fill their fields in arrays ? #include <iostream> #include <stdlib.h> #include <stdio.h> using namespace std; union complex; union complex{ int i1; long double ld1; } u; struct Person { char* name; int age; bool sex; void show(){ printf("name %s, age %2.0d, sex %1d\n", name , age, sex); }; } person; int main(void) { Person *o = new Person[2]; complex *un = new complex[2]; un[0]->i1=i; system("pause"); return 0; } I've tried un[0]-i1=i; but it's not the proper way to do this.

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  • LINQ to Entites - Left Outer Join - SQL 2000

    - by user255234
    Hi! I'm using Linq to Entities. I have the following query in my code, it includes left outer Join: var surgeonList = (from item in context.T1_STM_Surgeon.Include("T1_STM_SurgeonTitle") .Include("OTER").Include("OSLP") join reptable in context.OSLP on item.Rep equals reptable.SlpCode into surgRepresentative where item.ID == surgeonId select new { ID = item.ID, First = item.First, Last = item.Last, Rep = (surgRepresentative.FirstOrDefault() != null) ? surgRepresentative.FirstOrDefault().SlpName : "N/A", Reg = item.OTER.descript, PrimClinic = item.T1_STM_ClinicalCenter.Name, Titles = item.T1_STM_SurgeonTitle, Phone = item.Phone, Email = item.Email, Address1 = item.Address1, Address2 = item.Address2, City = item.City, State = item.State, Zip = item.Zip, Comments = item.Comments, Active = item.Active, DateEntered = item.DateEntered }) .ToList(); My DEV server has SQL 2008, so the code works just fine. When I moved this code to client's production server - they use SQL 2000, I started getting "Incorrect syntax near '(' ". I've tried changing the ProviderManifestToken to 2000 in my .edmx file, then I started getting "The execution of this query requires the APPLY operator, which is not supported in versions of SQL Server earlier than SQL Server 2005." I tied changing the token to 2005, the "Incorrect syntax near '(' " is back. Can anybody help me to find a workaround for this? Thank you very much in advance!

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  • memcmp,strcmp,strncmp in C

    - by el10780
    I wrote this small piece of code in C to test memcmp() strncmp() strcmp() functions in C. Here is the code that I wrote: #include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char** argv) { char *word1="apple",*word2="atoms"; if (strncmp(word1,word2,5)==0) printf("strncmp result.\n"); if (memcmp(word1,word2,5)==0) printf("memcmp result.\n"); if (strcmp(word1,word2)==0) printf("strcmp result.\n"); } Can somebody explain me the differences because I am confused with these three functions?My main problem is that I have a file in which I tokenize its line of it,the problem is that when I tokenize the word "atoms" in the file I have to stop the process of tokenizing.I first tried strcmp() but unfortunately when it reached to the point where the word "atoms" were placed in the file it didn't stop and it continued,but when I used either the memcmp() or the strncmp() it stopped and I was happy.But then I thought,what if there will be a case in which there is one string in which the first 5 letters are a,t,o,m,s and these are being followed by other letters.Unfortunately,my thoughts were right as I tested it using the above code by initializing word1 to "atomsaaaaa" and word2 to atoms and memcmp() and strncmp() in the if statements returned 0.On the other hand strcmp() it didn't.It seems that I must use strcmp(). I have done google searches but I got more confused as I have seen sites and other forums to define these three differently.If it is possible for someone to give me correct explanations/definitions so I can use them correctly in my source code,I would be really grateful.

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  • Change a finder method w/ parameters to an association

    - by Sai Emrys
    How do I turn this into a has_one association? (Possibly has_one + a named scope for size.) class User < ActiveRecord::Base has_many :assets, :foreign_key => 'creator_id' def avatar_asset size = :thumb # The LIKE is because it might be a .jpg, .png, or .gif. # More efficient methods that can handle that are OK. ;) self.assets.find :first, :conditions => ["thumbnail = '#{size}' and filename LIKE ?", self.login + "_#{size}.%"] end end EDIT: Cuing from AnalogHole on Freenode #rubyonrails, we can do this: has_many :assets, :foreign_key => 'creator_id' do def avatar size = :thumb find :first, :conditions => ["thumbnail = ? and filename LIKE ?", size.to_s, proxy_owner.login + "_#{size}.%"] end end ... which is fairly cool, and makes syntax a bit better at least. However, this still doesn't behave as well as I would like. Particularly, it doesn't allow for further nice find chaining (such that it doesn't execute this find until it's gotten all its conditions). More importantly, it doesn't allow for use in an :include. Ideally I want to do something like this: PostsController def show post = Post.get_cache(params[:id]) { Post.find(params[:id], :include => {:comments => {:users => {:avatar_asset => :thumb}} } ... end ... so that I can cache the assets together with the post. Or cache them at all, really - e.g. get_cache(user_id){User.find(user_id, :include => :avatar_assets)} would be a good first pass. This doesn't actually work (self == User), but is correct in spirit: has_many :avatar_assets, :foreign_key => 'creator_id', :class_name => 'Asset', :conditions => ["filename LIKE ?", self.login + "_%"] (Also posted on Refactor My Code.)

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  • sum of square of each elements in the vector using for_each

    - by pierr
    Hi, As the function accepted by for_each take only one parameter (the element of the vector), I have to define a static int sum = 0 somewhere so that It can be accessed after calling the for_each . I think this is awkward. Any better way to do this (still use for_each) ? #include <algorithm> #include <vector> #include <iostream> using namespace std; static int sum = 0; void add_f(int i ) { sum += i * i; } void test_using_for_each() { int arr[] = {1,2,3,4}; vector<int> a (arr ,arr + sizeof(arr)/sizeof(arr[0])); for_each( a.begin(),a.end(), add_f); cout << "sum of the square of the element is " << sum << endl; } In Ruby, We can do it this way: sum = 0 [1,2,3,4].each { |i| sum += i*i} #local variable can be used in the callback function puts sum #=> 30 Would you please show more examples how for_each is typically used in practical programming (not just print out each element)? Is it possible use for_each simulate 'programming pattern' like map and inject in Ruby (or map /fold in Haskell). #map in ruby >> [1,2,3,4].map {|i| i*i} => [1, 4, 9, 16] #inject in ruby [1, 4, 9, 16].inject(0) {|aac ,i| aac +=i} #=> 30 EDIT: Thank you all. I have learned so much from your replies. We have so many ways to do the same single thing in C++ , which makes it a little bit difficult to learn. But it's interesting :)

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  • ERROR 2019 Linker Error Visual Studio

    - by Corrie Duck
    Hey I hope someone can tell me know to fix this issue I am having i keep getting an error 2019 from Visual studio for the following file. Now most of the functions have been removed so excuse the empty varriables etc. Error error LNK2019: unresolved external symbol "void * __cdecl OpenOneDevice(void *,struct _SP_DEVICE_INTERFACE_DATA *,char *)" (?OpenOneDevice@@YAPAXPAXPAU_SP_DEVICE_INTERFACE_DATA@@PAD@Z) referenced in function _wmain c:\Users\K\documents\visual studio 2010\Projects\test2\test2\test2.obj test2 #include "stdafx.h" #include <windows.h> #include <setupapi.h> SP_DEVICE_INTERFACE_DATA deviceInfoData; HDEVINFO hwDeviceInfo; HANDLE hOut; char *devName; // HANDLE OpenOneDevice(IN HDEVINFO hwDeviceInfo,IN PSP_DEVICE_INTERFACE_DATA DeviceInfoData,IN char *devName); // HANDLE OpenOneDevice(IN HDEVINFO HardwareDeviceInfo,IN PSP_DEVICE_INTERFACE_DATA DeviceInfoData,IN char *devName) { PSP_DEVICE_INTERFACE_DETAIL_DATA functionClassDeviceData = NULL; ULONG predictedLength = 0, requiredLength = 0; HANDLE hOut = INVALID_HANDLE_VALUE; SetupDiGetDeviceInterfaceDetail(HardwareDeviceInfo, DeviceInfoData, NULL, 0, &requiredLength, NULL); predictedLength = requiredLength; functionClassDeviceData = (PSP_DEVICE_INTERFACE_DETAIL_DATA)malloc(predictedLength); if(NULL == functionClassDeviceData) { return hOut; } functionClassDeviceData->cbSize = sizeof (SP_DEVICE_INTERFACE_DETAIL_DATA); if (!SetupDiGetDeviceInterfaceDetail(HardwareDeviceInfo, DeviceInfoData, functionClassDeviceData, predictedLength, &requiredLength, NULL)) { free( functionClassDeviceData ); return hOut; } //strcpy(devName,functionClassDeviceData->DevicePath) ; hOut = CreateFile(functionClassDeviceData->DevicePath, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0, NULL); free(functionClassDeviceData); return hOut; } // int _tmain(int argc, _TCHAR* argv[]) { hOut = OpenOneDevice (hwDeviceInfo, &deviceInfoData, devName); if(hOut != INVALID_HANDLE_VALUE) { // error report } return 0; } Been driving me mad for hours. Any help appreciated. SOLVED THANKS TO CHRIS :-) Add #pragma comment (lib, "Setupapi.lib") Thanks

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  • How to combine apache requests?

    - by Bruce
    To give you the situation in abstract: I have an ajax client that often needs to retrieve 3-10 static documents from the server. Those 3-10 documents are selected by the client out of about 100 documents in total. I have no way of knowing in advance which 3-10 documents the client will require. Additionally, those 100 documents are generated from database content, and so change over time. It seems messy to me to have to make 10 ajax requests for 10 separate documents. My first thought was to write a jsp that could use the include action. ie in pseudo code for (param in params){ jsp:include page="[param]" } But it turns out the tomcat doesn't just include the html resource, it recompiles it, generating a class file every time, which also seems wasteful. Does any one know of a neat solution for combining apache requests to static files to make one request, rather than several, but without the overhead of, for example, tomcat generating extra class files for each static file and regenerating them each time the static file changes? Thanks! Hopefully my question is clear - it's a bit long-winded.

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  • C++ polymorphism and slicing

    - by Draco Ater
    The following code, prints out Derived Base Base But I need every Derived object put into User::items, call its own print function, but not the base class one. Can I achieve that without using pointers? If it is not possible, how should I write the function that deletes User::items one by one and frees memory, so that there should not be any memory leaks? #include <iostream> #include <vector> #include <algorithm> using namespace std; class Base{ public: virtual void print(){ cout << "Base" << endl;} }; class Derived: public Base{ public: void print(){ cout << "Derived" << endl;} }; class User{ public: vector<Base> items; void add_item( Base& item ){ item.print(); items.push_back( item ); items.back().print(); } }; void fill_items( User& u ){ Derived d; u.add_item( d ); } int main(){ User u; fill_items( u ); u.items[0].print(); }

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  • Segmentation Fault when trying to push a string to the back of a list.

    - by user308012
    I am trying to write a logger class for my C++ calculator, but I'm experiencing a problem while trying to push a string into a list. I have tried researching this issue and have found some information on this, but nothing that seems to help with my problem. I am using a rather basic C++ compiler, with little debugging utilities and I've not used C++ in quite some time (even then it was only a small amount). My code: #ifndef _LOGGER_H_ #define _LOGGER_H_ #include <iostream> #include <list> #include <string> using std::cout; using std::cin; using std::endl; using std::list; using std::string; class Logger { private: list<string> *mEntries; public: Logger() { // Initialize the entries list mEntries = new list<string>(); } ~Logger() { // Release the list mEntries->clear(); delete mEntries; } // Public Methods void WriteEntry(string entry) { // *** BELOW LINE IS MARKED WITH THE ERROR *** mEntries->push_back(string(entryData)); } void DisplayEntries() { cout << endl << "**********************" << endl << "* Logger Entries *" << endl << "**********************" << endl << endl; for(list<string>::iterator it = mEntries->begin(); it != mEntries->end(); it++) { cout << *it << endl; } } }; #endif I am calling the WriteEntry method by simply passing in a string, like so: mLogger->WriteEntry("Testing"); Any advice on this would be greatly appreciated.

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  • Crash using WscRegisterForChanges.

    - by user335126
    I'm trying to use the WscRegisterForChanges with C++ function in Windows 7. Documentation located here: http://msdn.microsoft.com/en-us/library/bb432507(v=VS.85).aspx My problem is that even though the callback properly executes, the code crashes when it gets to the end of the callback's execution. Here's the code in question. It's very simple, so I'm not sure why it's crashing: #include #include #include void SecurityCenterChangeOccurred(void *param) { printf("Change occurred!\n"); } int main() { HRESULT result = S_OK; HANDLE callbackRegistration = NULL; result = WscRegisterForChanges( NULL, &callbackRegistration, (LPTHREAD_START_ROUTINE)SecurityCenterChangeOccurred, NULL); while(1) { Sleep(100); } return 0; } My call stack looks like this when the crash occurs: 00faf6e8() ntdll.dll!_TppWorkerThread@4() + 0x1293 bytes kernel32.dll!@BaseThreadInitThunk@12() + 0x12 bytes ntdll.dll!___RtlUserThreadStart@8() + 0x27 bytes ntdll.dll!__RtlUserThreadStart@8() + 0x1b bytes If I add ExitThread(0); to the end of SecurityCenterChangeOccurred, I get an error and the following trace (So I don't think I should be using ExitThread): Unhandled exception at 0x7799852b (ntdll.dll) in WscRegisterForChangesCrash.exe: 0xC000071C: An invalid thread, handle %p, is specified for this operation. Possibly, a threadpool worker thread was specified. ntdll.dll!_TpCheckTerminateWorker@4() + 0x3ca2f bytes ntdll.dll!_RtlExitUserThread@4() + 0x30 bytes WscRegisterForChangesCrash.exe!SecurityCenterChangeOccurred(void * param=0x00000000) Line 8 + 0xa bytes C++ wscapi.dll!WorkItemWrapper() + 0x19 bytes ntdll.dll!_RtlpTpWorkCallback@8() + 0xdf bytes ntdll.dll!_TppWorkerThread@4() + 0x1293 bytes kernel32.dll!@BaseThreadInitThunk@12() + 0x12 bytes ntdll.dll!___RtlUserThreadStart@8() + 0x27 bytes ntdll.dll!__RtlUserThreadStart@8() + 0x1b bytes Does anyone have any ideas why this might be happening? To trigger the crash run the program and turn the firewall on or off.

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  • C++ iterator and const_iterator problem for own container class

    - by BaCh
    Hi there, I'm writing an own container class and have run into a problem I can't get my head around. Here's the bare-bone sample that shows the problem. It consists of a container class and two test classes: one test class using a std:vector which compiles nicely and the second test class which tries to use my own container class in exact the same way but fails miserably to compile. #include <vector> #include <algorithm> #include <iterator> using namespace std; template <typename T> class MyContainer { public: class iterator { public: typedef iterator self_type; inline iterator() { } }; class const_iterator { public: typedef const_iterator self_type; inline const_iterator() { } }; iterator begin() { return iterator(); } const_iterator begin() const { return const_iterator(); } }; // This one compiles ok, using std::vector class TestClassVector { public: void test() { vector<int>::const_iterator I=myc.begin(); } private: vector<int> myc; }; // this one fails to compile. Why? class TestClassMyContainer { public: void test(){ MyContainer<int>::const_iterator I=myc.begin(); } private: MyContainer<int> myc; }; int main(int argc, char ** argv) { return 0; } gcc tells me: test2.C: In member function ‘void TestClassMyContainer::test()’: test2.C:51: error: conversion from ‘MyContainer::iterator’ to non-scalar type ‘MyContainer::const_iterator’ requested I'm not sure where and why the compiler wants to convert an iterator to a const_iterator for my own class but not for the STL vector class. What am I doing wrong?

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