Re: For what reasons?

From: Daniel Schüle (uval_at_rz.uni-karlsruhe.de)
Date: 03/30/05 

Date: Wed, 30 Mar 2005 15:13:47 +0200

Bob Jenkins wrote:
> Its not neccessary to return a pointer in a method/function, right ?

you mean .. return pointer from the function
no, not necessary

> But for what reasons/under what circumstances do we have to do that ?

mostly to prevent copying or to be able to *work* with the same object

struct X {
double d;
int i;
char big[1024];
};

// expensive call to foo

X * addToI(X * x, int inc)
{
        x->i += inc;
        return x;
}

X * writeToBig(X * x, const char * what)
{
        strncpy(x->big, what, 1024);
        return x;
}

#include <iostream>
int main()
{
        X x = {0.0, 0, ""};
        writeToBig( addToI(&x, 1) , "hallo World");
        std::cout << x.big << x.big << std::endl;
}

as you can see, you can nest the calls to functions
and you work with the same object
cout verifies the changes

or imagine something like this

char * foo(int number)
{
        static char big[1024];
        sprintf(big, "your number was = %i", number);
        return big;
}
it wouldn't work without static and you would be forced to copy it
somewhere else ..

hope this helps

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