C++ celsius to fahrenheit 3 times - c++

Question

I'm learning C++, and to do that I have created myself a problem which is to convert Celsius to Fahrenheit three times in the console. The user will input the Celsius degree.
I also want the output to be displayed like this:
Celsius: Fahrenheit:
cel1 fahr1
cel2 fahr2
cel3 fahr3
The code I have tried so far is:
double cel1, cel2, cel3;
double fahr1, fahr2, fahr3;
cout << "Celsius degree one: ";
cin >> cel1;
cout << "Celsius degree two: ";
cin >> cel2;
cout << "Celsius degree three: ";
cin >> cel3;
fahr1 = (cel1 * 9) / 5 + 32;
fahr2 = (cel2 * 9) / 5 + 32;
fahr3 = (cel3 * 9) / 5 + 32;
// messy like this to display like I want to
cout << endl <<
"Celsius: " << "Fahrenheit:" << endl <<
cel1 << " " << fahr1 << endl <<
cel2 << " " << fahr2 << endl <<
cel3 << " " << fahr3 << endl << endl;
which will display like I want to, but I feel this could have been achieved in a simpler way, so I tried something like this with a loop, but I couldn't figure out how to do it properly:
double celsius;
for (int times = 0; times != 3; ++times){
cout << "Celsius degree: ";
cin >> celsius;
double fahrenheit = (celsius * 9) / 5 + 32;
cout << "Fahrenheit degree: " << fahrenheit << endl;
cin.clear();
}
This code is less then the previous one, gives the correct answer and will convert three times, but I couldn't figure out how to display it like I want to.
My question is what is the best way to do this?

Answer 1

I suggest to split the code into smaller functions:
The one to compute the conversion
double celsius_to_fahrenheit(double celsius)
{
return (celsius * 9.0) / 5.0 + 32.0;
}
The one to get the input, I choose to use std::vector as container.
you may choose std::array<double, 3> since the array have fixed size,
but std::vector is a good default choice.
std::vector<double> get_input_celsius(std::size_t size)
{
std::vector<double> celsius(size);
for (std::size_t i = 0; i != celsius.size(); ++i) {
std::cout << "Celsius degree " << (i + 1) << ": ";
std::cin >> celsius[i];
}
return celsius;
}
The method to display the result. I choose to not store the conversion in a new std::vector since it is not used afterward:
void display_celsius_and_fahrenheit(const std::vector<double>& celsius)
{
std::cout << std::endl << "Celsius: " << "Fahrenheit:" << std::endl;
for (auto c : celsius) { // for range since C++11
std::cout << c << " " << celsius_to_fahrenheit(c) << std::endl;
}
}
And finally the main function:
int main()
{
std::vector<double> celsius = get_input_celsius(3);
display_celsius_and_fahrenheit(celsius);
return 0;
}
Live example

Answer 2

Create arrays to store the temperatues.
Instead of
double cel1, cel2, cel3;
double fahr1, fahr2, fahr3;
use
double celsius[3];
double fahrenheit[3];
Change the input gathering loop to use the arrays.
for (int times = 0; times != 3; ++times){
cout << "Celsius degree: ";
cin >> celsius[times];
fahrenheit[times] = (celsius[times] * 9) / 5 + 32;
cin.clear();
}
Use a loop to create the output:
cout << endl << "Celsius: " << "Fahrenheit:" << endl <<
for (int times = 0; times != 3; ++times){
cout << celsius[times] << " " << fahrenheit[times] << endl;
}
You could get away with not creating the array fahrenheit too if you compute it only during output.
In that case, change the input gathering loop to:
for (int times = 0; times != 3; ++times){
cout << "Celsius degree: ";
cin >> celsius[times];
cin.clear();
}
Change the output loop to:
cout << endl << "Celsius: " << "Fahrenheit:" << endl <<
for (int times = 0; times != 3; ++times){
double fahrenheit = (celsius[times] * 9) / 5 + 32;
cout << celsius[times] << " " << fahrenheit << endl;
}