New variable or compound math statement

[Fenrar Muaddib]

I'm writing a program to calculate the miles per gallon that a vehicle delivers. The user inputs the liters consumed and the miles that the car traveled, and then a function calculates the miles per gallon.

I'm wondering which of the following functions would be better programming form: creating a new variable or using a compound math statement. I know for something this simple it probably doesn't matter, but I want to go ahead and get into good habits. So if this were a more complicated program that I was doing professionally, which of these should I use?

*note: LITERS_PER_GALLON is a globally defined const, because that's what the question in my book wanted me to do.

Here is the function using a compound math statement (no new variable):

double milesPerGallon (double litersConsumed, double milesTraveled)
{
    return (milesTraveled / (litersConsumed * LITERS_PER_GALLON));
}

This version seems like it would save on resources. Why create a new variable if you don't actually need it, right?

Here is the function using a new variable:

double milesPerGallon (double litersConsumed, double milesTraveled)
{
    double gallons;

    gallons = litersConsumed * LITERS_PER_GALLON;
    return (milesTraveled / gallons);
}

This version seems like it would make the function easier to understand for other programmers.

Thanks for any tips you guys can provide on this.

[MiiNiPaa]

It does not actually matters. Both are fine. I would use second probably but write it like that:

double milesPerGallon (double litersConsumed, double milesTraveled)
{
    //↓Initialize variable as soon as it is declared.
    double gallonsConsumed = litersConsumed / LITERS_PER_GALLON;
    return milesTraveled / gallonsConsumed ;
}

That code is self documented which might be useful when you have more complex equations

Also please note that you should divide liters on LITERS_PER_GALLON (or multiply it on GALLONS_PER_LITER) to get gallons