fractions

fractions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Globalization;

namespace MySuit.MySuitV2.BLL
{
    public class Utility
    {
        public static decimal FractionToDecimal(string frac)
        {
            // this method should convert a fraction, e.g. "12 1/4" to a decimal, e.g. 12.25.
            // based on http://amrelgarhytech.blogspot.com/2008/03/fraction-to-decimal.html
            // TODO: not sure how best to handle exceptions here. (parse errors, div by zero, null/empty string input...)
            decimal rv;
            int numerator, denominator, wholePart = 0;
            int sign = 1;

            if (string.IsNullOrEmpty(frac))
                return 0m;

            // deal with signs
            frac = frac.Trim().TrimStart('+');
            if (frac[0] == '-')
            {
                frac = frac.TrimStart('-');
                sign = -1;
            }
            frac = frac.Trim();

            if (frac.IndexOf("/") > 0)
            {
                if (frac.IndexOf(" ") > 0)
                {
                    wholePart = int.Parse(frac.Substring(0, frac.IndexOf(" ")));
                    frac = frac.Substring(frac.IndexOf(" "));
                }
                numerator = int.Parse(frac.Substring(0, frac.IndexOf("/")));
                denominator = int.Parse(frac.Substring(frac.IndexOf("/") + 1));
                rv = sign * (wholePart + ((decimal)numerator / denominator));
            }
            else
            {
                rv = decimal.Parse(frac);
            }
            return rv;
        }

        public static string DecimalToFractionSigned(decimal value)
        {
            // always put a sign (+/-) in front
            string rv = DecimalToFraction(value);
            if (rv[0] != '-')
                rv = string.Format("+{0}", rv);
            return rv;
        }

        public static string DecimalToFraction(decimal value)
        {
            // taken from here: http://bit.ly/tHaKrK and modified to work with negative numbers too.

            int sign = 1;
            if (value < 0)
            {
                value = Math.Abs(value);
                sign = -1;
            }

            // get the whole value of the fraction
            decimal mWhole = Math.Truncate(value);

            // get the fractional value
            decimal mFraction = value - mWhole;

            // initialize a numerator and denominator
            uint mNumerator = 0;
            uint mDenominator = 1;

            // ensure that there is actually a fraction
            if (mFraction > 0m)
            {
                // convert the value to a string so that you can count the number of decimal places there are
                string strFraction = mFraction.ToString().Remove(0, 2);

                // store the number of decimal places
                uint intFractLength = (uint)strFraction.Length;

                // set the numerator to have the proper amount of zeros
                mNumerator = (uint)Math.Pow(10, intFractLength);

                // parse the fraction value to an integer that equals [fraction value] * 10^[number of decimal places]
                uint.TryParse(strFraction, out mDenominator);

                // get the greatest common divisor for both numbers
                uint gcd = GreatestCommonDivisor(mDenominator, mNumerator);

                // divide the numerator and the denominator by the greatest common divisor
                mNumerator = mNumerator / gcd;
                mDenominator = mDenominator / gcd;
            }

            // create a string builder
            StringBuilder mBuilder = new StringBuilder();

            // add the whole number if it's greater than 0
            if (mWhole > 0m)
            {
                mBuilder.Append(mWhole);
            }

            // add the fraction if it's greater than 0m
            if (mFraction > 0m)
            {
                if (mBuilder.Length > 0)
                {
                    mBuilder.Append(" ");
                }

                mBuilder.Append(mDenominator);
                mBuilder.Append("/");
                mBuilder.Append(mNumerator);
            }

            if (sign == -1)
                mBuilder.Insert(0, '-');

            return mBuilder.ToString();
        }


        private static uint GreatestCommonDivisor(uint valA, uint valB)
        {
            // return 0 if both values are 0 (no GSD)
            if (valA == 0 && valB == 0)
            {
                return 0;
            }
            // return value b if only a == 0
            else if (valA == 0 && valB != 0)
            {
                return valB;
            }
            // return value a if only b == 0
            else if (valA != 0 && valB == 0)
            {
                return valA;
            }
            // actually find the GSD
            else
            {
                uint first = valA;
                uint second = valB;

                while (first != second)
                {
                    if (first > second)
                    {
                        first = first - second;
                    }
                    else
                    {
                        second = second - first;
                    }
                }

                return first;
            }
        }

    }
}