Add/remove to decimal places for greater and smaller sign

Question

I want to convert string values to decimal. When there is a smaller or greater symbol I want to add/remove to the value like this

string value  |  decimal result
--------------|----------------
 "< 0.22"     |   0.219
 "< 32.45"    |   32.449
 "> 2.0"      |   2.01
 "> 5"        |   5.1

This has to work for decimal numbers with any number of decimal places. Is there an elegant way to do this?

I can only think of counting the number of decimal places, getting the last digit, adding/removing ...

Answer 1

Using Regex

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] inputs = {
                "< 0.22",
                "< 32.45",
                 "> 2.0"
                             };
            string pattern = @"(?'sign'[\<\>])\s+(?'integer'\d+).(?'fraction'\d+)";

            decimal number = 0;
            foreach(string input in inputs)
            {
                Match match = Regex.Match(input, pattern);
                if(match.Groups["sign"].Value == ">")
                {
                   number = decimal.Parse(match.Groups["integer"].Value  + "." + match.Groups["fraction"].Value);
                   number += decimal.Parse("." + new string('0', match.Groups["fraction"].Value.Length) + "1");
                }
                else
                {
                   number = decimal.Parse(match.Groups["integer"].Value  + "." + match.Groups["fraction"].Value);
                   number -= decimal.Parse("." + new string('0', match.Groups["fraction"].Value.Length) + "1");
                }

                    Console.WriteLine(number.ToString());
            }
            Console.ReadLine();

        }
    }
}

Answer 2

So I would imagine the following solution

1. Split the string on the space
2. Identify the sign (GT or LT)
3. Count the number of decimal places and store that value
4. Convert the number to a decimal
5. Based on the symbol either add or subtract 10^(-1 * (numberOfDecimals + 1))

Answer 3

Solution without counting the decimals:

If the string starts with >, append "1". If the string starts with < replace the last character by the next lower one (Notice: for "0"->"9" and repeat on the character left to it) and then append "9". Then split at the blank and Double.Parse the right part.

Answer 4

No need to count digits or split apart the decimal... (you can run this in linqpad)

string inputString = "> 0.22";

string[] data = inputString.Split(' ');
double input = double.Parse(data[1]);
double gt = double.Parse(data[1] + (data[1].Contains('.') ? "1" : ".1"));

switch(data[0])
{
    case ">":
        gt.Dump(); // return gt;
        break;
    case "<":
        double lt = input - (gt - input);
        lt.Dump(); // return lt;
        break;
}

// you could even make it smaller by just doing (instead of the switch):
return data[0]==">" ? gt : input - (gt - input);

If trailing zeros are allowed as input but are considered insignificant then trim them.

inputString = inputString.TrimEnd("0");