Applied Programming/Loops/C++

loops.cpp

/*
This program converts a Fahrenheit temperature to Celsius.

Input:
Fahrenheit temperature

Output :
Fahrenheit temperature
Celsius temperature

Example :
Enter Fahrenheit temperature or press <Enter> to quit : 100

100.0 Fahrenheit is 37.8 Celsius!

F   C
100.0   37.8
101.0   38.3
102.0   38.9
103.0   39.4
104.0   40.0
105.0   40.6
106.0   41.1
107.0   41.7
108.0   42.2
109.0   42.8
110.0   43.3

Enter Fahrenheit temperature or press <Enter> to quit :

References :
https://stackoverflow.com/questions/7663709/how-can-i-convert-a-stdstring-to-int
https://en.cppreference.com/w/cpp/language/try_catch
https://www.geeksforgeeks.org/range-based-loop-c/

*/

#include <string>
#include <iostream>
using namespace std;

int ABSOLUTE_ZERO = -459.67;


double get_fahrenheit()
/*Gets Fahrenheit temperature.

Args:
  None

Returns:
  double: Fahrenheit temperature or "" if no temperature entered.

*/
{
  while (true){
    string fahrenheit;
    printf("\n\nEnter Fahrenheit temperature or press <Enter> to quit: ");
    getline(cin, fahrenheit);
    try {
      if (fahrenheit == "") {
        return 0;
      } else if (std::stod(fahrenheit) <= ABSOLUTE_ZERO){
        printf("\nError: Fahrenheit temperature cannot be below absolute zero! (-459.67)");
      } else {
        return std::stod(fahrenheit);
      }
    } catch(...) {
      cout << "\n" << "Error: |" << fahrenheit << "| is not a valid input!";
    }
  }
}


float fahrenheit_to_celsius(double fahrenheit)
/*Converts Fahrenheit temperature to Celsius.

Args:
  fahrenheit (double): Fahrenheit temperature to be converted

Returns:
  double: Celsius temperature

Raises:
  Error: A catastrophic error has occored!

*/
{
  int TEMPERATURE_DIFFERENCE = 32;
  double RATIO_ONE = 5;
  double RATIO_TWO = 9;
  double TEMPEATURE_RATIO = RATIO_ONE / RATIO_TWO;

	try {
		double celsius = (fahrenheit - TEMPERATURE_DIFFERENCE) * TEMPEATURE_RATIO;
    return celsius;
	} catch(...) {
    printf("Error: A catastrophic error has occored!");
	}
}


void display_results(double fahrenheit, double celsius)
/*Displays Fahrenheit and Celsius temperatures.

Args:
  fahrenheit (double): Fahrenheit temperature
  celsuis (double): Celsius temperature

Returns:
  None

*/
{
  printf("\n%.1f Fahrenheit is %.1f Celsius!\n", fahrenheit, celsius);
}


void display_table(double fahrenheit)
/*Displays nearest multiples of 10 Fahrenheit and Celsius temperatures.

Args:
  fahrenheit (float): Fahrenheit temperature

Returns:
  None

*/
{
  printf("\nF\tC");
  int start = int(fahrenheit / 10) * 10;
  int end = int(fahrenheit + 11);
  for (start; fahrenheit < end; fahrenheit += 1){
    double celsius = fahrenheit_to_celsius(fahrenheit);
    printf("\n%.1f\t", fahrenheit);
    printf("%.1f", celsius);
  }
}


int main()
// Runs the main program logic. //
{
  while (true){
    try {
      double fahrenheit = get_fahrenheit();
      if (fahrenheit == 0) {
        printf("\nExiting...");
        break;
      }
      float celsius = fahrenheit_to_celsius(fahrenheit);
      display_results(fahrenheit, celsius);
      display_table(fahrenheit);
    } catch(...) {
      printf("An unexpected error has occurred!");
      printf("\nExiting...");
      break;
    }
  }
}

Try It

Copy and paste the code above into one of the following free online development environments or use your own C++ compiler / interpreter / IDE. Applied Programming/IDE/C++/Online/Free

See Also

• C++
• Wikibooks: C++ Programming