Thread: Function not returning value

I think I'm missing something about passing variables to functions. This small program doesn't do what I want it to do. Its suppose to print a = 0 then call the function then print a=5, but it prints a=0 both times... what am I missing?

Code:

#include <iostream>

using namespace std;

int blabla(int b);

int main()
{
   int a=0;
   cout<<"a = "<<a<<" before function call."<<endl;
   blabla(a);
   cout<<"a = "<<a<<" after function call."<<endl;
}

int blabla(int b);
{
    b=5;
    return b;  
}

i don't exactly know what it is your doing but if your declaring that a = o then it will always = 0

You need to assign the function call to something, else, the returned result is not useable.

Code:

 a = blabla(a)

here

Code:

#include <iostream>

using namespace std;

int blabla(int b);

int main()
{
   int a=0;
   cout<<"a = "<<a<<" before function call."<<endl;
   cin.get();
   a = blabla(a);
   cout<<"a = "<<a<<" after function call."<<endl;
   cin.get();
}

int blabla(int b)
{
    b=5;
    return b;  
}

This wont modify var a in main() coz b is not pointing at a.
if you want to modify the content of a then you need to pass it by reference.

e.g

Code:

void test( int * );

int main()
{
   int y = 9; // cur value is 9
   test( &y ); //& for passing the memory address of variable y.
   return 0;
}

void test( int *i ) // i points to variable y in main()
{
    *i = 8; // i is pointing to y so modifying the value of *i also modifies the value of y.

}

*edited

used PHP tag

in c++ it is easier to use references rather than pointers which may be messy.

Code:

void blah(int &b){
    b = 5;
}
int main(){
a =0;
blah(a);
cout<<a;
return 0;
}

might do the work...

Ok, I think I got it. Thanks for the help ^_^

Originally Posted by wart101

i don't exactly know what it is your doing but if your declaring that a = o then it will always = 0

just to clarify in case anyone else reads this, that is not correct.

declaring
int a = 0;
makes an integer a with the value 0. There is nothing to stop you changing the value later.

a = 1;
a = 2;
a = 666;