Doesn't it allocate the class static variable to the heap, thus executing its algorithm then destroying it when the program ends - or. What exactly does it tell me? When the static variable is initialized, it takes place first before any of my other functions?
I am wrapping up a Linux/C programming assignment that requires several small programs for encrypting and decrypting text. There is a bash grading script which will be used to assess the performance of my programs. The script runs fine on my local machine and all of my tests pass, but when I run everything on my University's server via SSH, the script is not behaving the same. I am fairly certain the error exists somewhere in my C code, because no other students are having this issue. The 4 main programs consist of 2 daemons which wait for clients to connect via sockets, and the two clients. There is a daemon/client pair for handling encryption, and another for handling decryption.
And here is a screenshot of what happens with the same files on the remote server:As you can see, in the 4th and 5th tests (where the program's output should read), it's instead showing "ssIgnore this message". In later tests (not pictured) there is another message that reads "ddServer to client message". This text appears nowhere in my code or the grading script, so it must be server-side.
I have a class containing a map member that I want to initialize at declaration time. I know I can do it in the cpp file but I'm having a problem with the order of initialization (static initialization order fiasco).
My questions are:
Is it possible that the scenario in which, the Test's constructor's implementation and the map initialization instruction are in the same cpp file and constructor is called when the map is not initialized yet, could happen?
Is it possible to initialize the map in class like I did? I get these errors:
in-class initialization of static data member 'std::map<std::basic_string<char>, Test*> Test::a' of incomplete type temporary of non-literal type 'std::map<std::basic_string<char>, Test*>' in a constant expression
If yes, does this initialization resolve the static initialization order fiasco?
class Test { public: static std::map<std::string, Test*> a = {};//this is an error Test(std::string ID) {
I am having a problem concerning a static const member variable I want to use to set a certain property of my class during development time. The question actually concerns proper implementation as I do have a solution that "works" at least. The variable should denote the size of a member array which I don't want to allocate on the heap due to serious performance issues. So here is my code:
//MyClass.h class MyClass{ public: static const int MyArraySize = 256; private: int MyArray[MyArraySize]; };
This works but it's not nice for two reasons:
1) It doesn't separate interface from implementation. I would prefer to define the variable in the corresponding .cpp file but it doesn't work:
//MyClass.h class MyClass{ public: static const int MyArraySize;
[Code] .....
If I delete the line int MyArray[MyArraySize]; the above code works but when I use it to define the size of the array I get a "constant expression expected" error for the line int MyArray[MyArraySize]; which makes sense as the compiler does not know the value of MyArraySize when he reaches int MyArray[MyArraySize]; and therefore can not allocate the memory. Of course I can move MyArray to the heap like that:
//MyClass.h class MyClass{ public: static const int MyArraySize; static const int MyValue;
[Code] .....
But as I mentioned before this causes a remarkable loss of performance.
Something like the following does not work:
//MyClass.h class MyClass{ public: static const int MyArraySize = (int) pow(2, 8); private: int MyArray[MyArraySize]; };
This gives a "constant expression expected" error for the line static const int MyArraySize = (int) pow(2, 8);
Interestingly the following code works:
//MyClass.h class MyClass{ public: static const int MyValue; };
//MyClass.cpp #include "MyClass.h" const int MyClass::MyValue = (int) pow(2, 8);
So if I use pow outside of the class definition I get no errors. Is there any solution to those problems? So what I want is: 1) Don't allocate the array on the heap 2) Separate interface from implementation 3) Being able to use functions like pow to define MyArraySize 4) Not use global variables
I tried to initialize the frames variable but when I go to debug it, it just gives me 30 errors compared to the one error when I don't initialize the frames variable.
#include "Gfx.h" // general gfx lib I made for SDL #include "Input.h" #include "General.h" #include "Sprite.h" #define screenw 620 #define screenh 480
/** CHARS ARE DONE */ //int mousex; int mousey; int mouseon = 0; //int red = 0; int green = 0; int blue = 0;
I created a class (let call it X) which contains the structure to store the data from my data base. Them I have a class (call Y) which will contain a list for each row in my data base. Third, I have a class with thousands variables (Z). What I am trying to do is to take the list of objects (Y) that contains the data to initialize Z. What I want to now if I can do something like that.
Imaging that one of my rows contain the following data: Type Nameofvariable etc... "static const double; MNFAIL ; 0; 0; 0,25"
In my list I have a node with contain this data
I want to use the field Nameofvariable to initialize the variable called MNFAIL contained in my class Z.
I have 18,000 lines of code that i would like to upgrade to include a log file. I want to replace the cout with a stream or something similar so that i can easily output to the console and to a log file at the same time with minimal change to 18,000 lines of code. I'm nearly there.
I used this post heavily as a reference; [URL] .... however it is highly incomplete and this is above my knowledge so I'm struggling somewhat.
I was able to get the bulk of it working with some guess work and modification to the code from that link.
For some reason i had to comment out "mstream(void);" and "~mstream(void);"
to work for endl as per the previous link. Not sure if i'm even putting it in the right place. Otherwise the code works fine for streaming to both locations and such. See the code below;
#include <iostream> #include <fstream> #include <string> using namespace std; class mstream {
I'm trying to write something that when a user is at the command line, the user can type and it displays of list of commands the user can use to run the application.
is there a way to change output of console without clearing the screen? so making some kind of animation?
e.g.
I have used
Code: cout << "Hello";
is there any way I can erase last "lo" and replace it by "p" so I will have "Help" without clearing the screen ? just changing the output like some text file?
I tried using something like this
Code: #include <iostream> using namespace std; int main() { cout << "abcd"; long pos = cout.tellp(); cout.seekp(pos-2); cout.write("ef", 2); cout.flush(); cin.get(); return 0; }
I am currently doing a complex number calculator ,and i wish to output my data to a txt.file . i tried fstream and it doesnt work. However the txt.file was created but no text was output.
Below is the program:
#include<iomanip> #include<cmath> #include<iostream> #include<fstream> using namespace std; #define PI 3.14159265358979323 double z,x;
[Code]..
When impedance A & B are in series,the effective Impedance is " <<setprecision(4)<< z << " + j" <<setprecision(3)<< x<<endl;
else cout << "
When impedance A & B are in series,the effective Impedance is " <<setprecision(4)<<z << " - j" <<setprecision(3)<< x*(-1)<<endl; } void Complex::showdiv(double &z,double &x) { if ( x>= 0 ) cout << "
When impedance A & B are in parallel,the effective Impedance is " <<setprecision(4)<< z << " + j" <<setprecision(3)<< x <<endl; else cout << "
When impedance A & B are in parallel,the effective Impedance is " <<setprecision(4)<<z << " - j" <<setprecision(3)<< x*(-1) <<endl; }
class Polar:public Complex //inheritant from class Complex { protected: double r,d,r2,d2; public: void PolarValue(); void ShowPolar();
Alright, so to better myself with network logic I've decided to make a small net game.
I need to input commands to the console as well as output status updates at the same time. I'd prefer to write a gui interface for that, but I'd rather work with WinAPI as little as possible (I mean, look at the way it's designed...).
I'd like to do this with standard operations, limiting dependencies is a must for me.
I was exploring static variable by writing code snippets. I tried below code and it ended up throwing error saying "error: storage class specified for parameter 'b'"
Why static cannot be used in func() ?
Code: int main() { int a; a=5; func(a); printf("%d",a); return 0; }
If i declare 2 variables like this static int first, second; will both of them be declared static or will only first be declared static and second a regular variable?
I need to keep a static variable in a member function of a class that I have many objects of. I've had some trouble with it, and when I read up I found that such variables are static across all instances. Is there any way around this?
In a function, I have a static variable that I want to assign the time in seconds when a certain condition is met and keep that value until a different condition is met. The time value is a struct. Since now->sec is always incrementing, will timeWhenEventMadeActive below hold onto the initial value or will it increment every time the function is called? I cant seem to test this.
static time_t timeWhenEventMadeActive = 0; static bool initTime = 0; if (!initTime) { timeWhenEventMadeActive = now->sec; //holds uptime value in seconds
What is the problem with the following code is? It compiles with Visual C++ 2012 but does not with g++:
//a.h
#ifndef Loaded #define Loaded using namespace std; class MyClass{ public: static const int MyStaticValue = 200;
[Code] ....
If I try to compile this using the command
g++ a.cpp b.cpp
I get an "undefined reference to 'MyClass::MyStaticValue'" error for the line "A = MyClass::MyStaticValue;" in main(). The strange thing is that if I change the line to "A = (int) MyClass::MyStaticValue;" it works fine and the output is
200 200
as expected.
The code also compiles under g++ if I move the defintion of MyStaticValue from a.h to a.cpp by const int MyClass::MyStaticValue = 200;
