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Regex match for negative and positive numbers

hi:
  I am looking to check if the input string is a negative number or a positive number. How can I do this using Regex i.e I am looking for the pattern string to match all inputs against?

Thanks
0
LuckyLucks
Asked:
LuckyLucks
3 Solutions
 
Ravi SinghSenior Software EngineerCommented:
Hi, try the following regex, it should match both negative and positive numbers:

(-|\+)?\d+(\.\d+)?

Example:

using System.Text.RegularExpressions;
...
      string data = "-10";
      string regex = @"(-|\+)?\d+(\.\d+)?";

      Match m = Regex.Match(data, regex);

      if (m.Success)
      {
            MessageBox.Show("Matched: " + m.Value);
      }

is that what you were after?
0
 
der_jthCommented:
You should add a ^ in front and a $ to the end of Zephyr's regex. Other than that, it'll probably work okay. Without the string terminators (^ and $) it'll match anything that contains the appropriate number ("foo3", "a-5-b" etc. would all match).
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andrewjbCommented:
Do you want to accept .3 and -.3 (i.e. no leading '0' before the dot?)

In which case, change the middle \d+ to \d*

(Argh.. though that then accepts blank strings, so you might want to check against that, too!)
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LuckyLucksAuthor Commented:
Hi Zep,
Could u illuminate me on what the | and the \ geanerally mean and wr.t to the first bracket contents? thx
0
 
Ravi SinghSenior Software EngineerCommented:
Hi,

The | symbol allows you to match alternative tokens e.g. "cat|dog" will match either cat or dog. In our case we wanted to match either a minus or a plus sign at the beginning. (question mark is explained below)

The backslash \ character is used to escape characters that have special meaning in regular expressions. I escaped the + sign so that the regex engine takes it as a character plus symbol rather than its special meaning "one or more" in regular expressions.

The question mark symbol means "zero or none" of the previous symbol.... "\d" is short hand for any digit in the range 0-9. Finally, the dot was escaped using the backslash as it has a special meaning in regex's but we wanted it to simply mean a dot (decimal point in the input number).
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