How can string values be +ed?

[kevinkim]

I found some examples in the tutorial. which are :


string concatenate (string a, string b)
{
return a+b;
}
------------------------------------
string concatenate (string& a, string& b)
{
return a+b;
}
----------------------------------------

the string variables are not numbers, they are letters in sequence, as I know,
How can + operator process them? I tried to put them in my visual studio, but they didn't work.

[CodeWriter]

The + is an operator and in your example a and b are operands being operated on.
You could think of it this way,
+(string a,string b) or +(int a, int b)
What + means, that is, what operation is intended to take place, is determined by the operands. This is called overloading the operator just as you can overload a function.
If they are strings they are joined. If they are numbers they are added.

[kevinkim]

#include<iostream>
#include<stdlib.h>
#include<string>
using namespace std;

string concatenate(string a, string b) {
return a + b;
}

int main() {
string a,b;
a = "The first string"; b = "The second string";
cout << string;
system("pause");
}

this is the code I tried to see how it works. so it should be joined as your explain, but it just didn't join and didn't work. on what part is it wrong?

[CodeWriter]

You don't call concatenate from main so what is it used for?
cout << string ?????

#include<iostream>
#include<string>
using namespace std;

int main()
{
    string a,b;
    int n1,n2;
    a = "The first string";
    b = "The second string";
    n1 = 5;
    n2 = 6;
    cout << a + b << endl;
    cout << n1+n2 << endl;
return 0;
}

[kevinkim]

Your code worked good.

but my code was to execute the function concatenate and I wrote string instead of concatenate by mistake, thanks for letting me know that,

I corrected it as :

cout<< concatenate(a,b);
and it worked ! thank you !

[kevinkim]

by the way, I always put
#include <stdlib.h>
at the very first of my code and
system("pause");
at the end of the code.

it is to stay the console window so that I can look at the result with time.
or it just disappears just right after it appears.

do you guys don't do it?
and I just found it is why my console window process hangs..