c ++ | Temperature conversion | Celsius, Kelvin, Fahrenheit

temp_conversion.cpp

#include <iostream>
using namespace std;

//---------------Function Declaration----------------
void error(std::string); // returns error
bool valid_temp(double); // check for valid temprature in Kelvin | Below 0K is invalid
double ctok(double); // convert Celsius to Kelvin
double ktoc(double); // convert Kelvin to Celsius
double ftoc(double); // convert Fahrenheit to Celsius
double ctof(double); // convert Celsius to Fahrenhiet
double convertK(double, const char); // convert Kelvin to any
double convertC(double, const char); // convert Celsius to any
double convertF(double, const char); // convert Fahrenheit to any
double convert(double, const char, const char); // convert any to any
void getInput(double&, char& , char& ); // take input from user

// for dealing with error
class Invalid{}; // for invalid temprature
class Wrong{}; // for wrong format

int main()
{
    while(true){
        try{        
            double temp = 0;
            char ch1;
            char ch2 ;

            getInput(temp,ch1,ch2);
            double converted = convert(temp,ch1,ch2);
            
            std::cout << temp << ch1 << " = " << converted << ch2 <<std::endl;
        }
        catch(Invalid&){
            std::cout << "Invalid temperature !" <<std::endl;
        }
        catch(Wrong&){
            std::cout<< "Wrong Format !" <<std::endl;
        }
        catch(...){
            std::cout << "Somthing went wrong" <<std::endl;
        }
    }
}

// ----------------FUnction Definations----------------

// returns error
void error(std::string s)
{
    throw std::runtime_error(s);
}

// check for valid temprature in Kelvin | Below 0K is invalid
bool valid_temp(double k)
{
    if(k >= 0) return true;
    return false;
}

// convert Celsius to Kelvin
double ctok(double c)
{
    double k = c + 273.15;
    if(!valid_temp(k)) throw Invalid();
    return k;
}

// convert Kelvin to Celsius
double ktoc(double k)
{
    double c = k - 273.15;
    if(!valid_temp(k)) throw Invalid();
    return c;
}

// convert Fahrenheit to Celsius
double ftoc(double f)
{
    double c = (f - 32) * (5.0/9);
    if(!valid_temp(ctok(c))) throw Invalid();
    return c;
}

// convert Celsius to Fahrenhiet
double ctof(double c)
{
    double f = c * (9.0/5) + 32;
    if(!valid_temp(ctok(c))) throw Invalid();
    return f;
}

// convert Kelvin to any
double convertK(double t, const char ch)
{
    switch(ch){
        case 'C' : case 'c' :
            return ktoc(t);
        case 'F' : case 'f' :
            return ctof(ktoc(t));
    }
    throw Wrong();
}

// convert Celsius to any
double convertC(double t, const char ch)
{
    switch(ch){
        case 'F' : case 'f' :
            return ctof(t);
        case 'K' : case 'k' :
            return ctok(t);
    }
    throw Wrong();
}

// convert Fahrenheit to any
double convertF(double t, char ch)
{
    switch(ch){
        case 'C' : case 'c' :
            return ftoc(t);
        case 'K' : case 'k' :
            return ctok(ftoc(t));
    }
    throw Wrong();
}

// convert any to any
double convert(double t, const char ch1, const char ch2)
{
    if (ch1 == ch2) return t;

    switch(ch1){
        case 'K': case 'k' :
            return convertK(t,ch2);
        case 'C': case 'c' :
            return convertC(t,ch2);
        case 'F': case 'f' :
            return convertF(t,ch2);
    }
    throw Wrong();
}

// take input from user
void getInput(double& t, char& ch1, char& ch2)
{
    std::cout << "Enter temprature : ";
    std::cin >> t >> ch1;
    std::cout << "[Kelvin:K , Celsius:C , Fahrenheirt:F]" <<std::endl;
    std ::cout << "Enter output unit :";
    std::cin >> ch2;
}