passing a function parameter by reference
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  1. #1
    Join Date
    Sep 2012
    Posts
    1

    passing a function parameter by reference

    Hello, I created the following code to pass the the variable 'inputVoltage' by reference to the function 'input'. It certainly works when I run the program, but I dont think it is a standard way of doing it, i.e. the use of '*' and '&' is not according to convention ?
    Or perhaps the way did it is acceptable ?
    Thanks for any confirmation either way.

    int input (double *inputVoltage);

    int main ( {
    double inputVoltage;
    input(&inputVoltage);
    return 0;
    }

    int input(double* inputVoltage)
    {
    cin >> *inputVoltage;
    etc.
    etc.
    }

  2. #2
    Join Date
    Apr 1999
    Posts
    27,427

    Re: passing a function parameter by reference

    Quote Originally Posted by fran1942 View Post
    Hello, I created the following code to pass the the variable 'inputVoltage' by reference to the function 'input'. It certainly works when I run the program, but I dont think it is a standard way of doing it, i.e. the use of '*' and '&' is not according to convention ?
    You're being confused with reference and the address-of operator. These entities use the same symbol ('&') but have vastly different meanings.

    In your example, you are not using references anywhere. You are passing the address-of inputVoltage to the function, not a reference.
    Code:
    int input (double *inputVoltage);   // expects a pointer to double
    int input (double& inputVoltage);   // expects a reference to double
    
    int main 
    {
        double inputVoltage;
        input(&inputVoltage);  // calls the pointer version
        input(inputVoltage); // calls the reference version
    }
    Regards,

    Paul McKenzie

  3. #3
    Join Date
    Jul 2005
    Location
    Netherlands
    Posts
    2,013

    Re: passing a function parameter by reference

    Quote Originally Posted by fran1942 View Post
    Hello, I created the following code to pass the the variable 'inputVoltage' by reference to the function 'input'. It certainly works when I run the program, but I dont think it is a standard way of doing it, i.e. the use of '*' and '&' is not according to convention ?
    Or perhaps the way did it is acceptable ?
    Your approach would be conventional if you were programming in C, because references don't exist is C.
    However, in C++ you do have the choice to use either a pointer or a reference for you function argument. Using a pointer only makes sense if a NULL pointer has a special meaning. In your case it doesn't, in fact it would cause a problem, so you should use a reference instead of a pointer to clearly communicate that your function really needs to have a valid variable to write to.
    Cheers, D Drmmr

    Please put [code][/code] tags around your code to preserve indentation and make it more readable.

    As long as man ascribes to himself what is merely a posibility, he will not work for the attainment of it. - P. D. Ouspensky

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