Thread: Doing the opposite in a conversion?

Ok the conversion from feet and inches to meters and centimeters (meters being an int and the remainder being converted into cm), but how can I do just the opposite?

See here's the code for feet and inches to meters and cm and it works perfectly:

Code:

#include <iostream>
using namespace std;

void userInput(double& feet, double& inches);
void convertUStoMetric(double& meters, double& centimeters);
void output(double meters, double centimeters);

int main()
{
	double unit, subunit;
	char redo = 'y';
	
	while (redo == 'y' || redo == 'Y')
	{
	
			userInput(unit, subunit);
			convertUStoMetric(unit, subunit);
			output(unit, subunit);
		
		cout << "Would you like to run it again? Y/N: ";
     	cin >> redo;
     	cout << "\n";
	}
	
	system("pause");
    return 0;   
}

void userInput(double& feet, double& inches)
{
	cout << "Enter the feet and inches with a space in between each: ";
	cin >> feet;
	cin >> inches;
	cout << "\n";	
}

void convertUStoMetric(double& meters, double& centimeters)
{
	double feet = meters;
	double inches = centimeters;


	meters = (feet + inches/12) * 0.3048;

	centimeters = (meters - (int)meters) * 100;
	//5 feet = 1.524 meters
	//.524 meters = 52.4 cm
	//6 inches = 15.24 cm
	//total = 1 meter and 67.64 cm


	meters = (int)meters;

}

void output(double meters, double centimeters)
{
	cout << "The converted measurements are " << meters << " meters and " << centimeters << " centimeters.";
	cout << "\n\n";	
}

But when I try just the opposite for meters and cm to feet and inches, the feet is correct, but the cm is completely messed up.

Code:

#include <iostream>
using namespace std;

void userInput(double& meters, double& centimeters);
void convertMetricToUS(double& feet, double& inches);
void output(double feet, double inches);

int main()
{
	double unit, subunit;
	char redo = 'y';
	
	while (redo == 'y' || redo == 'Y')
	{
	
			userInput(unit, subunit);
			convertMetricToUS(unit, subunit);
			output(unit, subunit);
		
		cout << "Would you like to run it again? Y/N: ";
     	cin >> redo;
     	cout << "\n";
	}
	
	system("pause");
    return 0;   
}

void userInput(double& meters, double& centimeters)
{
	cout << "Enter the meters and centimeters with a space in between each: ";
	cin >> meters;
	cin >> centimeters;
	cout << "\n";	
}

void convertMetricToUS(double& feet, double& inches)
{
	float meters = feet;
	float centimeters = inches;


	feet = (meters + centimeters*2.54) / 0.3048;

	inches = (feet - (int)feet) / 100;

	feet = (int)feet;
	
	//5 meter = 16.404 199 475 feet
	//0.404199475 feet = 0.00404199 inches
	//6 centimeter = 2.362 204 724 4 inch
	//total = 16 feet and 
	//onlineconversion.com

}

void output(double feet, double inches)
{
	cout << "The converted measurements are " << feet << " feet and " << inches << " inches.";
	cout << "\n\n";	
}

If you want to try it out, put in 5 0, and you should get 16 feet and 0 inches. But when I put 5 6, I get some crazy numbers. The cm to inches conversion is working how it's supposed to.

Any advice or tips on what I can do to fix this?

P.S. It's also not the exact opposite because I tried fixing it and failed, but I get essentially the same thing.

Originally Posted by sufoode

Code:

void convertMetricToUS(double& feet, double& inches)
{
	float meters = feet;
	float centimeters = inches;


	feet = (meters + centimeters/100) * 3.2808399;

	inches = (feet - (int)feet) * 12;

	feet = (int)feet;

}

Where'd you get 3.2808399 from?

Ah ok thanks for making me feel so stupid *thumbs up*

Now my final question. In my book it says I have to ask the user whether they would like to covert from feet and inches to meters and cm, or from meters and cm to feet and inches.

And I would have an if/else statement.

But I'm kind of confused. So combining these two functions, there would be 6 functions in total? And how would the if/else statement look like? We haven't exactly learned how to make an if/else statement that chooses between two programs yet.

I'm ahead of the rest of the class because I got these two done, so he hasn't explained it yet.

What you can do, is something like this:

Code:

#include <iostream>

. . .

double convert_m_to_cm(double m) {
    return m/100.0;
}
double convert_cm_to_m(double cm) {
    return m * 100.0;
}
double convert_feet_to_inches(double feet) {
    return feet * 12.0;
}
double convert_inches_to_feet(double inches) {
    return inches / 12.0;
}
double inches_to_cm(double inches) {
    return inches / (whatever the ratio is);
}
double cm_to_inches(double cm) {
    return cm / (the other ratio);
}

int main(int argc, char *argv[]) {
    do {
        double value = 0.0;
        /* Step one: what is the original unit? */
        int first_unit_type = -1;
        /* Print out a message stating that 1 is cm, 2 is m, 3 is inches, 4 is feet . . . */
        if(first_unit_type == 2) value = convert_m_to_cm(value);
        else if(first_unit_type == 3) value = convert_inches_to_cm(value);
        else if(first_unit_type == 4) value = convert_feet_to_inches(convert_inches_to_cm(value));
        /* Step two: what is the desired unit? */
        int second_unit_type = -1;
        if(first_unit_type == 2) value = convert_cm_to_m(value);
        /* And so on for the other types . . . */
    } while(true);
    return 0;
}

See, by converting to a standardized base (I chose cm here, but you can use anything), you can then convert it into any desired base. I left out the printing, input, and error-checking statements, mainly because I didn't feel like typing them all out. When the user no longer wants to convert more measurements, then use a break statement to break out of the do/while loop.

Hope that helps.

Well I don't know about you guys, but I actually learn better if I'm just spoon fed the answers, then I can easily do something of the same level naturally. But that's just me.

Anyways I was able to combine both programs and ask the user which converter they would like to use with an if/else statement with my friend.

You guys really helped though, however sufoode actually used the same thing I was doing, like the void functions and nothing like print or something because I haven't even learned that material yet.

For some reason, whenever I ask a question here and show my code, half of everyone that replies uses some different output like //print and etc that I haven't learned yet which makes it really hard to even progress when I'm reading your advice. For example that person that also posted code for me used something that I wasn't requesting and I had no idea what it was.

But I do agree when it comes to code it's better to let me be taught or else I won't understand at all for upcoming programming projects.

Just some food for thought...

Code:

/*
    The strange template business is a workaround for not 
    being able to call virtual functions within constructors
*/
template < typename Derived >
struct length
{
    template < typename Other >
    length( length< Other > const& rhs )
    : data( rhs.standard( ) / ratio( ) )
    {    }
    
    length( double value )
    : data( value )
    {    }    

/*
    The simulated virtual function
*/    
    double ratio( void ) const
    {
        return static_cast< Derived const* >( this )->ratio( );
    }

/*
    Standard conversion (eg: to metric)
*/    
    double standard( void ) const
    {
        return data * ratio( );
    }

/*
    Implicit conversion, for convenience
*/        
    inline operator double ( void ) const
    {
        return data;
    }

/*
    The data, in the derived format, obviously
*/    
    double data;
};

#define DEFINE_LENGTH( type, factor )\
struct type : length< type >\
{\
    template < typename Other >\
    type( length< Other > const& rhs )\
    : length< type >( rhs )\
    {    }\
\
    type( double value = 0 )\
    : length< type >( value )\
    {    }\
\
    double ratio( void ) const\
    {\
        return factor;\
    }\
}

/*
    Define some new types, and their relationship to metric
*/
DEFINE_LENGTH( meters, 1.0 );
DEFINE_LENGTH( miles, 1609.344 );
DEFINE_LENGTH( yards, 0.9144 );
DEFINE_LENGTH( feet, 0.3048 );
DEFINE_LENGTH( inches, 0.0254 );

#include <iostream>

/*
    Now we can automatically convert between any type!
*/
int main( void )
{
    using namespace std;
    miles mile = 1;
    cout << "Meters per mile: " << meters( mile ) << endl;
    cout << "Yards per mile: " << yards( mile ) << endl;
    cout << "Feet per mile: " << feet( mile ) << endl;
    cout << "Inches per mile: " << inches( mile ) << endl;
/*
    Or whatever...
*/
    cout << "Miles per mile: " 
    << miles( inches( meters( yards( inches( mile ) ) ) ) ) << endl;
    return 0;
}