Find and replace numbers in string with regex

Question

What I'm trying to achieve is to replace the numbers in the string with a new values calculated from the (match * int).

So the string input looks like:

500g Flour
14g Salt
7g Dry yeast
45ml Olive oil
309ml Water

And the result should look like this:

1000g Flour
28g Salt
14g Dry yeast
90ml Olive oil
618 ml Water

row["ingredients"] is a DataRow.

This is where I'm at:

System.Text.RegularExpressions.
        Regex.Replace(row["ingredients"].ToString(), 
                      @"[^/d]", Delegate(Match match) { return match * 2; },
                      RegexOptions.Multiline);

Any solution is greatly appreciated.

Possibly a silly question, but is there a reason why you don't double the salt along with the other ingredients? — dash
– dash, Commented Sep 14, 2012 at 21:33
does the 500g Flour 14g should be changed to 1000g Flour 28g Salt? if not , i think all the answers must be considered that. — Hamed
– Hamed, Commented Sep 14, 2012 at 21:36
Are you ever expecting fractions? You wouldn't want to "double" 1/4 liter to 2/8 liter. Same for decimal numbers (0.5 tablespoons doubled isn't 0.10 tablespoons)... — Tim Pietzcker
– Tim Pietzcker, Commented Sep 14, 2012 at 21:42
@James edited to avoid ambiguity, although it rather removes the context of my comment! — dash
– dash, Commented Sep 14, 2012 at 21:43

CaffGeek · Accepted Answer · 2014-11-19 14:32:33Z

4

The first problem is that your regex is only matching characters that are not a digit.

Correction: It is using forward slashes instead of a backslash, so it's matching anything that is not a slash or a d

Change your regex to @"\b(\d+)"

Here's a working example on dotnetfiddle.net

using System;
using System.Text.RegularExpressions;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var string1 = "500g Flour 14g Salt 7g Dry yeast 45ml Olive oil 309ml Water";

            var result = Regex.Replace(string1, @"\b(\d+)", Doubler, RegexOptions.Multiline);

            Console.WriteLine(result);

            Console.ReadKey();
        }

        private static string Doubler(Match match)
        {
            return (Convert.ToInt32(match.Value)*2).ToString();
        }
    }
}

edited Nov 19, 2014 at 14:32

answered Sep 14, 2012 at 21:32

CaffGeek

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6 Comments

Tim Pietzcker Over a year ago

Not by me, but your regex matches the literal string /w/, followed by one or more ds.

CaffGeek Over a year ago

@TimPietzcker, typo, those should have been backslashes, fixed

Tim Pietzcker Over a year ago

I still don't get the \w. Why do you want to match A380?

CaffGeek Over a year ago

Because I am losing my mind. Was thinking \w was for word boundary, it should have been \b

CaffGeek Over a year ago

@TimPietzcker, fixed, except the salt isn't doubling and I have to run, not sure what I missed...

|

Tim Pietzcker · Accepted Answer · 2012-09-14 21:34:25Z

1

[^/d] means "any character except slash or the letter d".

To match a number, use \d+.

answered Sep 14, 2012 at 21:34

Tim Pietzcker

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Comments

Mykola Kushnir · Accepted Answer · 2012-09-14 22:28:28Z

0

Hold different type of data into datarow is not good practice. In your sample: "500g Flour" - here you have ingredientValue, measureType, ingredientName. I would recommend create small data class which will represent this row, and all type of data it will be properties of this class.
Benefits are oblivious:
- No needs to replace with regex magic
- Easy to extend and modify

All what you need with regex is to create correct parser of provided data row. But for sure it's more easy then tricks with replace.

answered Sep 14, 2012 at 22:28

Mykola Kushnir

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Comments

Nick · Accepted Answer · 2012-09-15 17:05:50Z

0

void Main()
{
  string ingredients =
@"500g Flour
0.5g Salt
7g Dry yeast
45ml Olive oil
309ml Water";

  string pattern = @"(?:[0-9]+\.?[0-9]*|\.[0-9]+)";

  int multiple = 2;

  Regex.Replace(ingredients, pattern, m => (Convert.ToDecimal(m.Value)*multiple).ToString()).Dump();
}

I did this in LINQPad so don't worry about the Dump() that's just to output the result. And I changed salt to 0.5 just to show that it works with non integers. That pattern is the best I could come up with for matching integers and decimals (with or without any number before the decimal) so it'll match 17, 3.141592, or .5

answered Sep 15, 2012 at 17:05

Nick

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