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  • C++: Define simple string?

    - by Jason
    This thing is really wracking my mind. I'm learning C++ and I wanted to define a constant that I can use in another function, A short answer on how to do this will be fine.. Lets say at the beginning of my code I want to define this constant: //After #includes bool OS = 1; //1 = linux if (OS) { const ??? = "clear"; } else { const ??? = "cls"; } I don't know what type to use to define the "clear" string... I'm so confused. Later on I want to use it within a function: int foo() { system(::cls); //:: for global return 0; } How would I define the string up top, and use the string down below? I heard char only had one character and things... I'm not sure how to use , since it says it's converting string into const char or something.

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  • C++: conjunction of binds?

    - by Helltone
    Suppose the following two functions: #include <iostream> #include <cstdlib> // atoi #include <cstring> // strcmp #include <boost/bind.hpp> bool match1(const char* a, const char* b) { return (strcmp(a, b) == 0); } bool match2(int a, const char* b) { return (atoi(b) == a); } Each of these functions takes two arguments, but can be transformed into a callable object that takes only one argument by using (std/boost)bind. Something along the lines of: boost::bind(match1, "a test"); boost::bind(match2, 42); I want to be able to obtain, from two functions like these that take one argument and return bool, a callable object that takes two arguments and returns the && of the bools. The type of the arguments is arbitrary. Something like an operator&& for functions that return bool.

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  • C++ Why is the copy constructor implicitly called?

    - by ShaChris23
    Why is the Child class's copy constructor called in the code below? I mean, it automatically converts Base to Child via the Child copy constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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  • [c]how to take input for a character pionter without using fget?

    - by ashish yadav
    consider the code include int main() {char* a; scanf("%s",a);//&a and &a[0] give same results-crashes printf("%s",); return 0; } why does this code results in crashing?whereas this code using character array works fine? include int main() {char a[100]; scanf("%s",&a[0]);//works fine printf("%s",a); return 0; } the difference being character array and pointer?but i knew that pointer just points to the first element that is &a[0] should work fine but upper code crashes for all three that is a,&a and &a[0]? the main thing i would to gather is how can i take input of a character pointer if i insist on using scanf only? i apologize if i am not clear. thanks in advance:)

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  • non-scalar type requested

    - by lego69
    can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); virtual ~A(){}; virtual void foo(); void foo() const; operator int(); }; class B: public A { public: B(int initPlayer): A(initPlayer){}; ~B(){}; virtual void foo(); };

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  • Access to bytes array of a Bitmap

    - by Deulis
    1- In Windows CE, I have a Bitmap object in C#. 2- I have a C function in an extern dll that expects as parameters the pointer to a bytes array that represents an image in RGB565 format, width and height. This function will draw on this array of bytes. So I need to pass the byte array pointer of the Bitmap object, but I can find a practical way to get this pointer. One way is convert this Bitmap into a bytes array using a memory stream or something else, but it will create a new bytes array, so I will keep in memory both object, the Bitmap and the bytes array, but I don’t want it because the few available memory, that’s why I need to access to the bytes array of the bitmap object, not create a new bytes array. Anyone can help me?

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  • Click a button in another application

    - by sam
    I want yo use SendMessage or PostMessage to press a button in another app i have a sample code to do this but by getting Window Handle, but don't work also i used "WinDowse" to get required info. here is the code private const uint BM_CLICK = 0x00F5; private const uint WM_LBUTTONDOWN = 0x0201; private const uint WM_LBUTTONUP = 0x0202; private void PushOKButton(IntPtr ptrWindow) { WindowHandle = FindWindow(null, "Form1"); if (ptrWindow == IntPtr.Zero) return; IntPtr ptrOKButton = FindWindowEx(ptrWindow, IntPtr.Zero, "Button", "&Yes"); if (ptrOKButton == IntPtr.Zero) return; SendMessage(ptrOKButton, WM_LBUTTONDOWN, 0, 0); SendMessage(ptrOKButton, WM_LBUTTONUP, 0, 0); SendMessage(ptrOKButton, BM_CLICK, 0, 0); } is There a Compelete Suloution in c# ?

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  • Lifetime of implicitly casted temporaries

    - by Answeror
    I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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  • Dynamical array of strings in C

    - by Ir0nm
    I'm trying to make array of strings, I have function rLine which reads line from stdin, each inputted line I need to save in array, but I don't have any idea about number of inputted string lines. So I need to dynamically increase array size to store them, I wrote such code: char *res[2], *old = res; while( 1 ){ line = rLine( stdin ), len = strlen( line ); res[row] = (char*)malloc( len + 1); strcpy( res[row++], line); res = (char**) realloc( res, row ); /* adding 1 more row, not sure adding size row? */ if ( /*some cond*/ ) break; } But this code doesn't seem to work, how correctly declare array and increase it size?

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  • regular expression on replace method of js not working

    - by user950146
    why this is not working var value = arr[row][col].replace(new RegExp('"', 'g'),'""'); Error : Webpage error details User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; Tablet PC 2.0) Timestamp: Tue, 10 Apr 2012 11:22:01 UTC Message: Object doesn't support this property or method Line: 1041 Char: 25 Code: 0 URI: http://example.com/? Message: Object doesn't support this property or method Line: 1041 Char: 25 Code: 0 URI: http://example.com/? Message: Object doesn't support this property or method Line: 1041 Char: 25 Code: 0 URI: http://example.com/? Note: : Error copied directly from debugger of IE8

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  • Using variables within Attributes in C#

    - by tehp
    We have some Well-Attributed DB code, like so: [Display(Name = "Phone Number")] public string Phone { get; set; } Since it is quite generic we'd like to use it again, but with a different string in the Name part of the attribute. Since it's an attribute it seems to want things to be const, so we tried: const string AddressType = "Student "; [Display(Name = AddressType + "Phone Number")] public string Phone { get; set; } This seems to work alright, except that having a const string means we can't overwrite it in any base classes, thereby removing the functionality that we originally were intending to add, and exposing my question: Is there a way to use some sort of variable inside of an attribute so that we can inherit and keep the attribute decorations?

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  • c++: use a #define in printf?

    - by John
    I was wanting to use a constant of some kind for the application ID (so I can use it in printf). I had this: #define _APPID_ "Hello World!" And then the simple printf, calling it into %s (string). It put this out: simple.cpp:32: error: cannot convert ‘_IO_FILE*’ to ‘const char*’ for argument ‘1’ to ‘int printf(const char*, ...)’ What would I use to define the application ID to use in printf? I tried: static const char _APPID_[] = "Hello World"` but it didn't work, same error I think.

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  • strstr whole string match

    - by clay
    I'm trying to match the whole string and not just part of it. For instance, if the needle is 2, I would like to match just the string 2 and not 20, 02, or 22 or anything related. I'm using strstr as: #include <stdio.h> #include <string.h> int main(int argc, char *argv[]) { FILE *file; char l[BUFSIZ]; int linenumber = 1; char term[6] = "2"; file = fopen(argv[1], "r"); if(file != NULL) { while(fgets(l, sizeof(l), file)){ if(strstr(l, term) != NULL) { printf("Search Term Found at %d!\n", linenumber); } ++linenumber; } } else { perror(argv[1]); } fclose(file); return 0; }

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  • Best way to call other class view in iphone?

    - by aman-gupta
    Hi, Generally i call my other class view by creating a pointer of delegate and then call the other class by using its link as below:- First Way :- Mydelegate *ptr = (Mydelegate *)[[UIApplication sharedApplication]delegate]; [self.navigationController pushViewController:ptr.NextClasspointer animated:YES]; Second Way :- Create a pointer of that class which u want to call :-- NextClass *nextptr = [[NextClass alloc]initWithnibName:@"NextClass" bundle:nil]; [self.navigationController pushViewController:nextptr animated:YES]; [nextptr release]; nextptr = nil; These above two methods i generally used but my problem is that which one is best for big project so that my stack problem will be removed I mean memory issue will be solved.And is it necessary to release pointer in first and second case is the way i release is correct or wrong Please help me Thanks in Advance

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  • Simple 'database' in c++

    - by DevAno1
    Hello. My task was to create pseudodatabase in c++. There are 3 tables given, that store name(char*), age(int), and sex (bool). Write a program allowing to : - add new data to the tables - show all records - sort tables with criteria : - name increasing/decreasing - age increasing/decreasing - sex Using function templates is a must. Also size of arrays must be variable, depending on the amount of records. I have some code but there are still problems there. Here's what I have: Function tabSize() for returning size of array. But currently it returns size of pointer I guess : #include <iostream> using namespace std; template<typename TYPE> int tabSize(TYPE *T) { int size = 0; size = sizeof(T) / sizeof(T[0]); return size; } How to make it return size of array, not its pointer ? Next the most important : add() for adding new elements. Inside first I get the size of array (but hence it returns value of pointer, and not size it's of no use now :/). Then I think I must check if TYPE of data is char. Or am I wrong ? // add(newElement, table) template<typename TYPE> TYPE add(TYPE L, TYPE *T) { int s = tabSize(T); //here check if TYPE = char. If yes, get the length of the new name int len = 0; while (L[len] != '\0') { len++; } //current length of table int tabLen = 0; while (T[tabLen] != '\0') { tabLen++; } //if TYPE is char //if current length of table + length of new element exceeds table size create new table if(len + tabLen > s) { int newLen = len + tabLen; TYPE newTab = new [newLen]; for(int j=0; j < newLen; j++ ){ if(j == tabLen -1){ for(int k = 0; k < len; k++){ newTab[k] = } } else { newTab[j] = T[j]; } } } //else check if tabLen + 1 is greater than s. If yes enlarge table by 1. } Am I thinking correct here ? Last functions show() is correct I guess : template<typename TYPE> TYPE show(TYPE *L) { int len = 0; while (L[len] == '\0') { len++; } for(int i=0; i<len; i++) { cout << L[i] << endl; } } and problem with sort() is as follows : Ho can I influence if sorting is decreasing or increasing ? I'm using bubble sort here. template<typename TYPE> TYPE sort(TYPE *L, int sort) { int s = tabSize(L); int len = 0; while (L[len] == '\0') { len++; } //add control increasing/decreasing sort int i,j; for(i=0;i<len;i++) { for(j=0;j<i;j++) { if(L[i]>L[j]) { int temp=L[i]; L[i]=L[j]; L[j]=temp; } } } } And main function to run it : int main() { int sort=0; //0 increasing, 1 decreasing char * name[100]; int age[10]; bool sex[10]; char c[] = "Tom"; name[0] = "John"; name[1] = "Mike"; cout << add(c, name) << endl; system("pause"); return 0; }

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  • Method sscanf() ambiguous behavior

    - by Carmen Cojocaru
    I am trying to understand how sscanf() works. I ran some examples from this page: http://docs.roxen.com/pike/7.0/tutorial/strings/sscanf.xml and they don't work on my platform. I can't understand why. For instance: "sscanf("4711bar", "%d%s", a, b);" makes the program exit with an error... Here is one of the examples that work: "sscanf("foo", "f%s", a);". Does anybody know why? Do they work on your platforms? Thank you. This is my code: int main(void){ char *b = (char*)malloc(sizeof(char)*100); int a = 0; sscanf("4711bar", "%d%s", a, b); printf("%d", a); printf("%s", b); }

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  • Will creating index help in this case

    - by The King
    I'm still a learning user of SQL-SERVER2005. Here is my table structure CREATE TABLE [dbo].[Trn_PostingGroups]( [ControlGroup] [char](5) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [PracticeCode] [char](5) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL, [ScanDate] [smalldatetime] NULL, [DepositDate] [smalldatetime] NULL, [NameOfFile] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, [DepositValue] [decimal](11, 2) NULL, [RecordStatus] [char](1) COLLATE SQL_Latin1_General_CP1_CI_AS NULL, CONSTRAINT [PK_Trn_PostingGroups_1] PRIMARY KEY CLUSTERED ( [ControlGroup] ASC, [PracticeCode] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] Scenario 1 : Suppose I have a query like this... Select * from Trn_PostingGroups where PracticeCode = 'ABC' Will indexing on Practice Code seperately help me in making my query faster?? Scenario 2 : Select * from Trn_PostingGroups where ControlGroup = 12701 and PracticeCode = 'ABC' and NameOfFile = 'FileName1' Will indexing on NameOfFile seperately help me in making my query faster ??

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  • C++ cin problems. not capturing input from user

    - by user69514
    I have the following method which is not capturing anything from the user.If I input New Band for the artist name, it only captures "New" and it lefts out "Band". If I use cin.getline() instead nothing is captured. Any ideas how to fix this? char* artist = new char [256]; char * getArtist() { cout << "Enter Artist of CD: " << endl; cin >> artist; cin.ignore(1000, '\n'); cout << "artist is " << artist << endl; return artist; }

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  • C++ performance, optimizing compiler, empty function in .cpp

    - by Dodo
    I've a very basic class, name it Basic, used in nearly all other files in a bigger project. In some cases, there needs to be debug output, but in release mode, this should not be enabled and be a NOOP. Currently there is a define in the header, which switches a makro on or off, depending on the setting. So this is definetely a NOOP, when switched off. I'm wondering, if I have the following code, if a compiler (MSVS / gcc) is able to optimize out the function call, so that it is again a NOOP. (By doing that, the switch could be in the .cpp and switching will be much faster, compile/link time wise). --Header-- void printDebug(const Basic* p); class Basic { Basic() { simpleSetupCode; // this should be a NOOP in release, // but constructor could be inlined printDebug(this); } }; --Source-- // PRINT_DEBUG defined somewhere else or here #if PRINT_DEBUG void printDebug(const Basic* p) { // Lengthy debug print } #else void printDebug(const Basic* p) {} #endif

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  • c++: strange syntax in what() method of std::exception

    - by Patrick Oscity
    When i am inheriting from std::exception in order to define my own exception type, i need to override the what() method, which has the following signature: virtual const char* what() const throw(); This definitely looks strange to me, like if there were two method names in the signature. Is this some very specific syntax, like with pure virtual methods, e.g.: virtual int method() const = 0; or is this a feature, that could somehow be used in another context, too? And if so, for what could it be used?

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  • C++: static function member shared between threads, can block all?

    - by mhambra
    Hi all, I have a class, which has static function defined to work with C-style extern C { static void callback(foo bar) { } }. // static is defined in header. Three objects (each in separate pthread) are instantiated from this class, each of them has own loop (in class constructor), which can receive the callback. The pointer to function is passed as: x = init_function(h, queue_id, &callback, NULL); while(1) { loop_function(x); } So each thread has the same pointer to &callback. Callback function can block for minutes. Each thread object, excluding the one which got the blocking callback, can call callback again. If the callback function exists only once, then any thread attempting to callback will also block. This would give me an undesired bug, circa is interesting to ask: can anything in C++ become acting this way? Maybe, due to extern { } or some pointer usage?

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  • How to define a custom iterator in C++

    - by Robert Martin
    I've seen a number of posts on SO about how to define custom iterators, but nothing that seems to exactly answers my question, which is... How do I create an iterator that hides a nested for loop? For instance, I have a class Foo, inside of the Foo is a Bar, and inside of the Bar is a string. I could write for (const Foo& foo : foo_set) for (const Bar& bar : foo.bar_set) if (bar.my_string != "baz") cout << bar.my_string << endl; but instead I want to be able to do something like: for (const string& good : foo_set) cout << good << endl; How do I do something like this?

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  • C++ string array from ifstream

    - by David Beck
    I have a program that I need to read in an array of strings from a file. The array must be C type strings (char * or char[]). Using the following code, I get a bad access error: for (i = 0; i < MAX_WORDS && !inputFile.eof(); i++) { inputFile >> words[i]; } words is declared as: char *words[MAX_WORDS];

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  • Determine an object's class returned by a factory method (Error: function does not take 1 arguments

    - by tzippy
    I have a factorymethod that either returns an object of baseclass or one that is of derivedclass (a derived class of baseclass). The derived class has a method virtual void foo(int x) that takes one argument. baseclass however has virtual void foo() without an argument. In my code, a factory method returns a pointer of type bar that definetly points to an object of class derivedclass. However since this is only known at runtime I get a compiler error saying that foo() does not take an argument. Can I cast this pointer to a pointer of type derivedclass? std::auto_ptr<baseclass> bar = classfactory::CreateBar(); //returns object of class derivedclass bar->foo(5); class baseclass { public: virtual void foo(); } class derivedclass : public baseclass { public: virtual void foo(int x); }

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  • Testing for the presence of a character in an string in C

    - by Prab
    What's wrong with this? #include <stdio.h> void main(){ char *s="some text"; printf("%d",is_in(s,'t')); } int is_in(char *s, char c){ while(*s){ if(*s==c) return 1; s++; } return 0; } I get the following compile time error with GCC: test.c:9: error: conflicting types for ‘is_in’ test.c:9: note: an argument type that has a default promotion can’t match an empty parameter name list declaration test.c:5: note: previous implicit declaration of ‘is_in’ was here

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