[SOLVED]no error reporting，but cout doesn't work

nimingzhe2008

my code

@#include<QApplication>
#include<iostream>
using namespace std;

class IntArray
{
int length;
int *data;
public: IntArray():length(0),data(0)
{}
IntArray(int x)
{
length=x;
data=new int[x];
}
int& operator[](int x)
{
return data[x];
}

};

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

IntArray m(6);
m[3]=9;

cout<<m[3];

return app.exec();
}@

when I compiled it,nothing happened.Help,please.

sierdzio

You are not actually using QApplication here, so you can drop those 2 lines. Please wrap your code in '@' tags, it's hard to read it in it's current form.

guziemic

well, first of all please use '@ '@ code markers. So you code will be more readable.

Regarding you example, I am also using cout and I did not have any problems. You code also looks correct, with only one exception. If you are using cout and then goes into main loop

@
app.exec()
@

then you will not see output on console. If you will just call

@
return 0;
@

then you will see your output. You can always use qDebug() to see output if you need main loop in you application.

broadpeak

What does this line:
m=9;
mean?

And:
cout << m;
This won't work because your IntArray has no "<<" operator.
(ostream& operator<<(ostream& os, const IntArray& ia);)

sierdzio

I think it's m [ 3 ], but the forum software changed that into an anchor.

broadpeak

I've found you a similar code,
from this you can understand the essentials:
@
#include <iostream>
#include <sstream>
#include <cstring>

using namespace std;

class IntArray {
enum { sz = 5 };
int i[sz];
public:
IntArray() { memset(i, 0, sz* sizeof(*i)); }
int& operator[](int x) { return i[x]; }
friend ostream& operator<<(ostream& os, const IntArray& ia);
friend istream& operator>>(istream& is, IntArray& ia);
};

ostream& operator<<(ostream& os, const IntArray& ia)
{
for(int j = 0; j < ia.sz; j++)
{
os << ia.i[j];
if(j != ia.sz -1) os << ", ";
}
os << endl;
return os;
}

istream& operator>>(istream& is, IntArray& ia)
{
for(int j = 0; j < ia.sz; j++) is >> ia.i[j];
return is;
}

int main()
{
stringstream input("47 34 56 92 103");
IntArray I;
input >> I;
I[4] = -1;
cout << 1;
cout << I;
}
@

guziemic

In my opinion, you do not have to define operator for << because you return int which is of know type for cout in overloaded operator []

issam

my code

@
#include<QApplication>
#include<iostream>
using namespace std;

class IntArray
{
private:
int length;
int *data;

public:
IntArray():length(0),data(0)
{
}

         IntArray(int x) 
         { 
             length=x; 
             data=new int[x]; 
         } 

         int& operator[](int x) 
         { 
           return data[x]; 
         }

};

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

IntArray m(6);
m[3]=9;

cout<<m[3];

return app.exec();
}
@

:)

is it clear no ! :(

issam

And where is the implementation of

@operator=()@

?
m() is an object not an array !

You have not a GUI so you can write :

@return 0;@

nimingzhe2008

Thanks everyone.There is something wrong with my .pro file.Now it works.