passing by reference

[samuelweaver21]

I'm trying to pass by reference. I know you have to add an ampersand to the function prototype, but im not quite sure what i am supposed to put in the function description.

 #include <iostream>
using namespace std; 

 double celsius_to_fahrenheit(double);


int main()
 {
  
  double fahrenheit;
  double celsius = 22.5;


  fahrenheit = celsius_to_fahrenheit(celsius);

  cout << celsius << " C = " << fahrenheit << " F\n";
  system ("pause");
  return 0;
 } 

double celsius_to_fahrenheit (double &celsius)
 {
  return(celsius * (9.0/5.0) + 32.0);
 
 }

[giblit]

Umm..Firstly you need amperstand in your prototype secondly that's not how you use references you would return void and set a new value for celsius and it will directly modify the varaible being passed as a param.

celsius *= (9.0/5.0);
celsius += 32;

[LB]

A temperature conversion function is not a good candidate for pass-by-reference - you should try with something else instead.

[norm b]

The function definition has to match the declaration. You can leave out the variable name(s) in the definition but they are usually included for clarity.
So double celsius_to_fahrenheit(double &); will compile
but double celsius_to_fahrenheit(double &celsius); is preferred.

[Stewbond]

Passing by reference is best used in two situations (of which neither apply here):
1) The object passed is a complex class which will be expensive to copy
2) You want to modify the original object in your function

Also, when I declare references i like to do this double& celsius instead of double &celsius. This is a personal preference but I like it because in this case, & is not getting the address, but is part of the type. You are saying "I want a reference to a double". Similarly, for pointers I like: double* celsius over double *celsius. I only attach the * to the object when I am dereferencing.

So to answer your question directly, you would do this:

void setToZero(double& value);

int main()
{
    double something;
    setToZero(something); // something gets set to 0.0;
}

void setToZero(double& value)
{
    value = 0.0;
}

[samuelweaver21]

thank you for the feedback. The reason i am using this program is because the book i bought to self teach myself gave me this as a project.

[LB]

What is the book called?