Thread: passing variables

Originally Posted by 182

Hey guys, I have two newbie questions, is it possible to pass an ifstream variable to a function the same way you can pass an integer variable?

Yes, you'll usually want to pass it as a non-const reference argument since any changes to the stream (the state of the stream) made within the function should be kept when the function exits.

Originally Posted by 182

I was also wondering when cin.getline is used as follows is it better to use a string or an array?

Well, you can use either version depending on your needs; but, cin.getline() is only for character arrays, the string form of that function looks a little bit different: getline(cin,name_of_string).

>is it possible to pass an ifstream variable to a function the same way you can pass an integer variable?
Yes, but you should pass a reference (&). In fact some compilers give you an error if it's not a reference or pointer.

Code:

void foo( ifstream &in )

>I was also wondering when cin.getline is used as follows is it better to use a string or an array?
A string is the modern C++ way:

Code:

string ch;
cout<<"enter something"<<endl;
getline(cin, ch);

Yes, you could use a string object in place of the character array by simply substituing the string variable name in place of the character array name. One whitespace separated word would be read each iteration through the loop. A string object would be more space efficient taking up less stack space.

To see what the theoretical maximum size for a string is, use the max_size member function.

Code:

string str;
cout << str.max_size() << endl;

My output:

Code:

4294967293

Thanks guys

What does your function call look like?

Code:

#include <fstream>

void PASS_IFSTREAM(std::ifstream &foo) {}

int main() 
{
    std::ifstream foo;
    
    PASS_IFSTREAM(foo);   // not PASS_IFSTREAM(&foo)
}

>Anyone have anyidea what the problem could be?
Leave off the & when calling the function. The compiler already knows it's a reference, when it sees the function's definition.

Code:

foo( name_of_ifstream );