unitConverter

/*
 * File:   unitConverter.c
 * Author: Nathan
 *
 * A Book On C: Fourth Edition. Chapter 2, Exercise 9
 * A program that converts between ounces, pounds, grams, and kilograms
 * uses symbolic constants defined in conversions.h for the conversion factors
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "conversions.h" //contains conversion factors


char fromUnit[50] = "No Unit";
char toUnit[50] = "No Unit";
double input = 0.0;
double output = 42.0; //the answer to life, the universe, and everything

int main(int argc, char** argv) {

beginning:

    printf("Input the value you would like to convert.\n");
   if  (scanf("%lf", &input) != 1){//how do I ensure this value is not passed to convertmore?
       printf("Invalid value. It must be a double.\n");
       goto convertmore;
   } //takes an input value as a double


    printf("Input the unit of your value. (ounce/pound/gram/kilogram)\n");
    scanf("%s", fromUnit); //takes a unit type as a string

    printf("Input the unit to convert the value to. (ounce/pound/gram/kilogram)\n");
    scanf("%s", toUnit); //takes a unit type as a string




    if (strcmp(fromUnit, "ounce") == 0) { //from ounces
        if (strcmp(toUnit, "pound") == 0) { //to pounds
            output = input / 16; //an ounce is 1/16 of a pound
        } else if (strcmp(toUnit, "gram") == 0) { //to grams
            output = input * OUNCESTOGRAMS;
        } else if (strcmp(toUnit, "kilogram") == 0) { //to kilograms
            output = (input * OUNCESTOGRAMS) / 1000; // convert ounces to grams first,  and then to kilograms
        }

    } else if (strcmp(fromUnit, "pound") == 0) { //from pounds
        if (strcmp(toUnit, "ounce") == 0) { //to ounces
            output = input * 16; //an ounce is 16 pounds
        } else if (strcmp(toUnit, "gram") == 0) { //to grams
            output = input * POUNDSTOGRAMS;
        } else if (strcmp(toUnit, "kilogram") == 0) {//to kilograms
            output = (input * POUNDSTOGRAMS) / 1000; //convert pounds to grams first, and then to kilograms
        }


    } else if (strcmp(fromUnit, "gram") == 0) { //from grams
        if (strcmp(toUnit, "ounce") == 0) { //to ounces
            output = input * GRAMSTOOUNCES;
        } else if (strcmp(toUnit, "pound") == 0) { //to pounds
            output = input * GRAMSTOPOUNDS;
        } else if (strcmp(toUnit, "kilogram") == 0) {//to kilograms
            output = input / 1000; // kilogram is 1/1000 of a gram
        }


    } else if (strcmp(fromUnit, "kilogram") == 0) { //from kilograms
        if (strcmp(toUnit, "ounce") == 0) { //to ounces
            output = (input * 1000) * GRAMSTOOUNCES; //convert to grams first, then grams to ounces
        } else if (strcmp(toUnit, "pound") == 0) {
            output = (input * 1000) * GRAMSTOPOUNDS; //convert to grams first, and then to pounds
        } else if (strcmp(toUnit, "gram") == 0) {
            output = input * 1000; // a gram is 1000 kilograms
        }

    } else if (strcmp(fromUnit, toUnit) == 0) { //if the units are the same
        output = input; //the output is the same as the input
    }

    else {
        printf("Unsupported unit type\n");
        goto convertmore;
    }


    printf("%lf %s is equal to %lf %s\n", input, fromUnit, output, toUnit);

convertmore:
    printf("Would you like to perform additional conversions? (y/n)\n");
    char str[50];
    scanf("%s", str);
    if (strcmp(str, "y") == 0 || strcmp(str, "yes") == 0) {
        goto beginning;
    } else {
        printf("Exiting.\n");
        return (EXIT_SUCCESS);
    }
}

/*
 * File:   conversions.h
 * Author: Nathan
 */

    #define POUNDSTOGRAMS 453.59237
    #define GRAMSTOPOUNDS 0.00220462262
    #define OUNCESTOGRAMS 28.3495231
    #define GRAMSTOOUNCES 0.0352739619