CODEWITHSUNDEEP
regexnsregularexpression
digitalmasters
digitalmasters

Reputation: 68

Regular Expression. Find integers only

Find only the integers in a math equation...

5 + 5.5 + 6 / 2.0

I want to find the 5 and the 6 not the 5.5 or the 2.0 To find decimals I use \d+(.\d{1,})

I've tried \b\d+\b but that finds all the digits

Upvotes: 1

Views: 10425

Answers (3)

crowebird
crowebird

Reputation: 2586

Could try this:

/(?:^|[^\.])(\d+)(?:\s+|$)/

Make sure a digit(s) does not start with a dot, or is the beginning of the string, and makes sure the digit(s) are followed by a space, or the end of the string.

Here is a PHP example in action:

preg_match_all('/(?:^|[^\.])(\d+)(?:\s+|$)/', '5 + 5.5 + 6 / 2.0 + 33 * 16', $matches);
var_dump($matches);
/* Var Dump:
array (size=2)
  0 => 
    array (size=4)
      0 => string '5 ' (length=2)
      1 => string ' 6 ' (length=3)
      2 => string ' 33 ' (length=4)
      3 => string ' 16' (length=3)
  1 => 
    array (size=4)
      0 => string '5' (length=1)
      1 => string '6' (length=1)
      2 => string '33' (length=2)
      3 => string '16' (length=2)
*/

So what was captured was 5, 6, 33, and 16 (I added some longer digits to ensure it works)

Upvotes: 0

Gareth Bowen
Gareth Bowen

Reputation: 949

You could try to look for all digits, that don't have a "." in front, and have whitespace afterwards, like so:

[^\.]([0-9]+)\s

Upvotes: 0

Joni
Joni

Reputation: 111219

You can use negative lookbehind and lookahead, if that's supported by your regular expression engine. The regular expression would be:

(?<!\.)\d+(?!\.)

The lookbehind ensures that the string of digits does not begin with a ., so that something like .5 won't be matched. The lookahead ensures that the string of digits does not end with a ., so that 5. won't be matched.

Upvotes: 4

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