I have developed an application in C++ that creates some text files in a directory chosen by the user.
How can I ask the user set a Default Directory Path (and some other default parameters) so that she doesn't have to enter the same data in the GUI everytime the application is run.
The application has been developed using Qt Creator.
I'm asking how to create a function with default parameters with the possibility to init the parameters that you need.
Code Example :
#include <iostream>
int func(int a = 1, int b = 2, int c = 3, int d = 4) {
return a + b * c / d;
[Code] .....
[URL] ....
#include <iostream>
#include <vector>
void f(std::vector<int> const &v, std::vector<int>::const_iterator it = v.end()) {
} int main() {
f({}); }
prog.cpp:4:73: error: local variable ‘v’ may not appear in this context
void f(std::vector<int> const &v, std::vector<int>::const_iterator it = v.end())
Why is this not allowed? (I mean, what is the reasoning for defining the standard this way?)
In C++14/C++17 we will have a unified way to represent end iterators without an instance of the container, but currently I just have to hope my implementation accepts a default-constructed iterator as an end iterator.
In the thread "Making a argument optional to function", it is stated that to set default values for arguments of a function you can simply do so in the function definition, like:
int myfunc(int a, int b, int c=3) {...}
This then automatically puts c to 3 in the function body if a call like myfunc(1,2); is made, if I understood correctly. However, this does not seem to hold for class functions. For example, something like:
class classy {
public:
int class_func(int, int, int); // class function prototype
}
int classy::class_func(int a, int b, int c=3) {...}
fails to compile. What I would like is to be able to call class_func outside of this class (by including it as a header in another macro), optionally specifying c. If c is not specified in the call, it should use a default value.
I'm creating simple console application using Code::Blocks to allow me to pass parameters from other application to replace string within text/registry file before execute the registry merge. Passing parameters to console already success. Now I only have problem with reading file. Example of first line in the registry file is as below.
Windows Registry Editor Version 5.00
However when read into string and output to console using 'cout', it will be show as below with spaces in between.
W i n d o w s R e g i s t r y E d i t o r V e r s i o n 5 . 0 0
Below is my code.
ifstream f("install.reg");
string s((istreambuf_iterator<char>(f)), istreambuf_iterator<char>());
cout << s;
What happens if I make a server application using tcp protocol and then establish connection with a client application but the server crash and then the client send data. Will the data be lost or the system will continue trying to send it?
View 2 Replies View RelatedI want to create an application that starts an application and passes input to that application. I know how to start a process using the classes in System.Diagnostics, but I don't know how to pass data to the process.
For example, and this is just an example, I would like to be able to automatically start an application that requires a username and password and automatically enter the username and password. Of course, that might open the door to security vulnerabilities, but that's not the point of the exercise.
How to implement the functionality I described? Is there a general way to go about doing this or does it depend entirely on the idiosyncrasies of the application in question?
i have task scheduling application which execute every 30 minute i want to keep this process when system is log off in c# console application
View 2 Replies View RelatedFollowing is the code snippet
Code:
[COLOR=white !important]?
1
2
3
4
5 char str1[]="Bombay";
char str2[]="Pune";
char *s1=str,*s2=str2;
while(*s1++=*s2=str2);
printf("%s",str1);
Output of this code comes out to be Pune
But according to me output should be puneay.
Pune should be copied in place of Bomb.and rest should be as it is.
[/COLOR]
I have a problem. I want to set pointers to a default value for both 32 bit and 64 bit compiles. The 32-bit version works as:
enum constants { UNDEFINED = 0xDeadBeef }
if ((unsigned long)ptr == UNDEFINED)
but I can't seem to extend this to 64-bits. I've tried
#if __SIZEOF_POINTER__ == 4
enum constants { UNDEFDATA = 0xDeadBeef };
}; // enum constants
#elif __SIZEOF_POINTER__ == 8
enum constants { UNDEFDATA = 0xDeadBeefDeadBeef };
#endif
with:
if (ptr == UNDEFINED)
but get a message saying the '==' is undefined (I understand this)
Is there any way to setup so that I can change the size of my constants so that the comparisons will always work correctly? I've tried a 'typedef' but the compiler complains at
'typedef unsigned long long ADDR' // won't accept, and
static const SlipCellBase * const TEMPORARY = (SlipCellBase&)0xFFFFFFFFFFFFFFFF; // illegal conversion
enum doesn't work (because it's an int?)
First I wrote a Binary-tree class to draw a binary tree on the window. The nodes were small circles. Then I become wanted to change the shape of the nodes from circles to triangles by another class, Binary-tree-derived which is derived from Binary-tree class. I wrote the below code to do the job but I get two errors about constructors. First, code:
/* The binary-tree class, one of the topics that has been said in Programming Principles and Practice using C++ book by Biarne Stroustrup.
This code is written by R Abbasi (s.rabbasi@yahoo.com) */
#include <Simple_window.h>
[Code].....
Errors are:
Error12error C2512: 'Binary_tree' : no appropriate default constructor availablec:userscsdocumentsvisual studio 2012projects est_1 est_1 est_1.cpp91
13IntelliSense: no default constructor exists for class "Binary_tree"c:UsersCSDocumentsVisual Studio 2012Projects est_1 est_1 est_1.cpp91
How to create default arguments in C? Is there any way to make default arguments ( i mean any alternative for them).
View 5 Replies View RelatedHow do you write a default constructor?I need to use a default constructor that will initialize the data members:
- salesPerson to “Unknown”
- noOfWeek to 13
- amount to point to an array of thirteen 0.00s.
This is my weeklysales class
class WeeklySales {
char* salesPerson;
double* amount; // Pointer to an array
int noOfWeek; // Size of the array
};
Here's my attempted code:
//default constructor
WeeklySales (){
salesPerson="Unknown";
noOfWeek = 13;
amount = 0.00;
}
A compiler auto created default constructor is called a synthesized default constructor. It will initialize the built-in members to 0 or not depends on where the class object is defined? if I define a class
class point{
public:
double x, y;
};
if I define point point1; in global scope then point1.x and point1.y will be initialized to 0, if I define point point2; in a local scope, then its x and y won't be initialized? If it is like this, then I believe if there are built-in type members in a class, then the synthesized default constructor is almost useless!
I have an inherited class that essentially manages a Qt Window.
It is as follows (prototype below):
class QTMyOpenGLWindow : public QWindow, protected QOpenGLFunctions {
Q_OBJECT
[Code] ....
Now, I can understand the confusion of the compiler, but the functionality as I laid it out works for me (I can create the class with just specifying the parent and also have the option of preventing auto-initialization when creating). But, is there a better approach?
I am trying to figure out what's the best way to accomplish something like this:
void function(t1 a=0,t2 b=0){/*...*/};
t2 value;
function(value);
That would throw a compile error, since the first argument that is being passed to the function (value) is considered the first argument in the declaration (a), which is of type t1. So, is there a way to force my function to consider value as the second argument instead of the first one? I am aware that this could be done using overloading, but the larger the amount of arguments, the larger amount of possibilities, so it might end up with a huge list of overloads. The best case scenario would be being able to set things like:
void function(t1 a=16,t1 b=0,t2 c=1){/*body*/};
function(b=3,a=0);
but I'm not aware of such feature in C++.
Would it be possible to design some sort of macro system to take care of this?
So a long time ago I messed around with DirectX but I don't remember where it gets placed by default. I want to just get rid of the SDK and get the up to date version of it.
View 4 Replies View Relatedrefer to the code below, the attribute class is created with the value type and default value, but why it doesn't work for std::string?
#include <string>
#include <iostream>
using namespace std;
[Code].....
For example, I have an empty vector of integer. If I keep calling push_back on vector, is it going to be out of memory?
View 8 Replies View RelatedImplicit default ctor does not initialize the built-in data members, so what is it needed for?
View 5 Replies View RelatedI've been pondering which of these 2 approaches would make for the best interface for a library: Defining custom exceptions with specific names for different error scenarios but with standard behaviour, or simply using the predefined exceptions from the STL.
This is my current approach:
Code:
namespace rpp
{
class ConnectionError : public std::exception
{
public:
ConnectionError(const std::string &p_err);
[Code] .....
This seems to make for more descriptive code but it adds no functionality and the implementations are completely identical, which seems "off" to me, somehow.
I have a question about the default constructor.
To my best understanding, the compiler will provide me with a deafult constructor only if there are no any user defined constructors, at all. Now consider the following code:
Code: class MyClass
{
private:
int m_data;
public:
MyClass(int init):m_data(init){cout<<"Ctr called"<<endl;}
[Code] ....
How is it that suddenly, there is a default constructor?
Same solution that I was having compiler errors on yesterday. We're working with inheritance and the program is supposed to be to create and display information for default Employee objects, Hourly Employee objects and Salaried Employee objects. Everything compiles as is, but I'm running into two issues that I can't figure out.
1) In both the hourly and salaried objects, the wage, hours, and management level attributes all displaying their default values. I'm almost positive that this has something to do with the str to int and str to double conversions that I'm using (currently have atoi and atof in the file, but I've also tried stringstream, but still had to same problem). Any thoughts as to what I'm missing?
2) the assignment calls for the Benefit benefit member in Employee.h to be protected. However this makes the member unaccessible when I try to use it in the EmployeeMain.cpp in order to set the input for the Benefit class members. I had to make the Benefit benefit member public again to get it to compile. How would I set the input for the Benefit class members while the Benefit benefit member is protected?
Solution files follow:
EmployeeMain.cpp
Code:
#include "Hourly.h"
#include "Salaried.h"
void DisplayApplicationInformation();
void DisplayDivider(string);
string GetInput(string);
[Code]....
For example if using FindFirstFile(...) it assumes your passing LCPWSTR and not LPCSTR.
I know I can use FindFirstFileA or FindFirstFileW so what is point of default if always UNICODE.
Which brings to my second question. If I say
FindFirstFile("C:", &fdat);
I get error cannot convert parameter 1 from 'const char [7]' to 'LPCWSTR'
I could say WCHAR fName = "C:"; and pass this variable instead. However is there a way to cast "C:" on-the-fly to LPCWSTR, I tried,
FindFirstFile((LCPWSTR)"C:", &fdat);
But it outputs a stream of LONGs to the console instead of filenames.
I faced a compilation error in the following code :
Code:
#include <iostream>
using namespace std;
void addition(int a, int b = 2, int c);
int main()
[Code]......
My question is that when i have called addition() with the 3rd argument, then what is the necessity of having the default argument for the 3rd parameter ?
I would like to write a program that gives you a few default values. Now you can keep these values by pressing the enter key or you can change them by just typing in new ones and confirm the new values by pressing the enter key again.
Thats as far as i got on my own but it doesn't really work. what i can do to fix this.
Code:
#include<stdio.h>
#include <conio.h>
int getInt(int min, int max);
int main () {
int a[3] = {3,4};
int b;
int code;
[Code]...