Regexp only integer issue

Question

I found this regexp for integers from range -2147483648 to 2147483647.

(0|[1-9]{1}[0-9]{0,8}|[1]{1}[0-9]{1,9}|[-]{1}[2]{1}([0]{1}[0-9]{8}|[1]{1}([0-3]{1}[0-9]{7}|[4]{1}([0-6]{1}[0-9]{6}|[7]{1}([0-3]{1}[0-9]{5}|[4]{1}([0-7]{1}[0-9]{4}|[8]{1}([0-2]{1}[0-9]{3}|[3]{1}([0-5]{1}[0-9]{2}|[6]{1}([0-3]{1}[0-9]{1}|[4]{1}[0-8]{1}))))))))|(\+)?[2]{1}([0]{1}[0-9]{8}|[1]{1}([0-3]{1}[0-9]{7}|[4]{1}([0-6]{1}[0-9]{6}|[7]{1}([0-3]{1}[0-9]{5}|[4]{1}([0-7]{1}[0-9]{4}|[8]{1}([0-2]{1}[0-9]{3}|[3]{1}([0-5]{1}[0-9]{2}|[6]{1}([0-3]{1}[0-9]{1}|[4]{1}[0-7]{1})))))))))

Works for -2147483648 but not working for 2147483647, the last digit is problem no matter what number is.. 214748364 is valid...

I'm sure there are easier ways to validate this than a regex. — Oliver Charlesworth
– Oliver Charlesworth, Commented Dec 22, 2013 at 21:06
If someone writes a regex that uses {1} or [-], that's a clear sign that they don't know what they are doing. Avoid. — Tim Pietzcker
– Tim Pietzcker, Commented Dec 22, 2013 at 21:09
@milandjukic88 What language are you using? We’ll give you a better way than regular expressions. — poke
– poke, Commented Dec 22, 2013 at 21:10
@milandjukic88 Well, just set min="-2147..." and max="2147...". If you need to support older browsers, then parseInt(str, 10) the input value and compare it to your limits. — ComFreek
– ComFreek, Commented Dec 22, 2013 at 21:11

Vasili Syrakis · Accepted Answer · 2013-12-23 00:53:01Z

***************

Regexp is not made for matching arbitrary range numbers.

***************

This 'only' matches 0 - 2147483647.

First, break into equal length ranges:

0 - 9

10 - 99

100 - 999

1000 - 9999

10000 - 99999

100000 - 999999

1000000 - 9999999

10000000 - 99999999

100000000 - 999999999

1000000000 - 2147483647

Second, break into ranges that yield simple regexes:

0 - 9

10 - 99

100 - 999

1000 - 9999

10000 - 99999

100000 - 999999

1000000 - 9999999

10000000 - 99999999

100000000 - 999999999

1000000000 - 1999999999

2000000000 - 2099999999

2100000000 - 2139999999

2140000000 - 2146999999

2147000000 - 2147399999

2147400000 - 2147479999

2147480000 - 2147482999

2147483000 - 2147483599

2147483600 - 2147483639

2147483640 - 2147483647

Turn each range into a regex:

[0-9]

[1-9][0-9]

[1-9][0-9]{2}

[1-9][0-9]{3}

[1-9][0-9]{4}

[1-9][0-9]{5}

[1-9][0-9]{6}

[1-9][0-9]{7}

[1-9][0-9]{8}

1[0-9]{9}

20[0-9]{8}

21[0-3][0-9]{7}

214[0-6][0-9]{6}

2147[0-3][0-9]{5}

21474[0-7][0-9]{4}

214748[0-2][0-9]{3}

2147483[0-5][0-9]{2}

21474836[0-3][0-9]

214748364[0-7]

Collapse adjacent powers of 10:

[0-9]{1,9}

1[0-9]{9}

20[0-9]{8}

21[0-3][0-9]{7}

214[0-6][0-9]{6}

2147[0-3][0-9]{5}

21474[0-7][0-9]{4}

214748[0-2][0-9]{3}

2147483[0-5][0-9]{2}

21474836[0-3][0-9]

214748364[0-7]

Combining the regexes above yields:

([0-9]{1,9}|1[0-9]{9}|20[0-9]{8}|21[0-3][0-9]{7}|214[0-6][0-9]{6}|2147[0-3][0-9] {5}|21474[0-7][0-9]{4}|214748[0-2][0-9]{3}|2147483[0-5][0-9]{2}|21474836[0-3][0- 9]|214748364[0-7])

Next we'll try factoring out common prefixes using a tree:

Parse into tree based on regex prefixes:

. [0-9]{1,9}

1 [0-9]{9}
2 0 [0-9]{8}
- 1 [0-3] [0-9]{7}
  - 4 [0-6] [0-9]{6}
  - 7 [0-3] [0-9]{5}
    - 4 [0-7] [0-9]{4}
    - 8 [0-2] [0-9]{3}
      - 3 [0-5] [0-9]{2}
      - 6 [0-3] [0-9]
        
        4 [0-7]

Turning the parse tree into a regex yields:

([0-9]{1,9}|1[0-9]{9}|2(0[0-9]{8}|1([0-3][0-9]{7}|4([0-6][0-9]{6}|7([0-3][0-9]{5}|4([0-7] [0-9]{4}|8([0-2][0-9]{3}|3([0-5][0-9]{2}|6([0-3][0-9]|4[0-7])))))))))

We choose the shorter one as our result.

\b([0-9]{1,9}|1[0-9]{9}|2(0[0-9]{8}|1([0-3][0-9]{7}|4([0-6][0-9]{6}|7([0-3][0-9]{5}|4([0-7] [0-9]{4}|8([0-2][0-9]{3}|3([0-5][0-9]{2}|6([0-3][0-9]|4[0-7])))))))))\b

Tim Pietzcker · Accepted Answer · 2013-12-22 21:21:01Z

1

I'm answering this question not because I think it's a good idea to do this with a regex but because I may have uncovered a bug in RegexMagic while having it construct this monster for me:

^(?:-?(?:214748364[0-7]|21474836[0-3][0-9]|2147483[0-5][0-9]{2}|214748[0-2][0-9]{3}|21474[0-7][0-9]{4}|2147[0-3][0-9]{5}|214[0-6][0-9]{6}|21[0-3][0-9]{7}|20[0-9]{8}|1[0-9]{9}|[1-9][0-9]{1,8}|[0-9])|-2147483648)$

or, broken down for "legibility":

^
(?:
 -?
 (?:
  214748364[0-7]
 |
  21474836[0-3][0-9]
 |
  2147483[0-5][0-9]{2}
 |
  214748[0-2][0-9]{3}
 |
  21474[0-7][0-9]{4}
 |
  2147[0-3][0-9]{5}
 |
  214[0-6][0-9]{6}
 |
  21[0-3][0-9]{7}
 |
  20[0-9]{8}
 |
  1[0-9]{9}
 |
  [1-9][0-9]{1,8}
 |
  [0-9]
 )
|
 -2147483648
)
$

answered Dec 22, 2013 at 21:21

Tim Pietzcker

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Comments

brandonscript · Accepted Answer · 2013-12-22 23:26:06Z

1

You can solve this with regex, but it's really not the right thing to do. Something like this will be infinitely more efficient:

function isValid(num)
{
    if (num >= -2147483648 && num <= 2147483647)
        return true;
    else
        return false
}

isValid(2147483646); //true
isValid(-2147483649); //false

edited Dec 22, 2013 at 23:26

answered Dec 22, 2013 at 21:20

brandonscript

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Comments

Pi Marillion · Accepted Answer · 2013-12-24 00:09:44Z

0

Using few groups for readability:

(?:(?:-|\b)(?:1?[0-9]{1,9}|20[0-9]{8}|21[0-3][0-9]{7}|214[0-6][0-9]{6}|2147[0-3][0-9]{5}|21474[0-7][0-9]{4}|214748[0-2][0-9]{3}|2147483[0-5][0-9]{2}|21474836[0-3][0-9]|214748364[0-7])|-2147483648)\b

Using groups like a tree-list to speed up searching:

(?:(?:-|\b)(?:1?[0-9]{1,9}|20[0-9]{8}|21(?:[0-3][0-9]{7}|4(?:[0-6][0-9]{6}|7(?:[0-3][0-9]{5}|4(?:[0-7][0-9]{4}|8(?:[0-2][0-9]{3}|3(?:[0-5][0-9]{2}|6(?:[0-3][0-9]|4[0-7]))))))))|-2147483648)\b

Obviously, it's most efficient to use (?:-|\b)[0-9]{0,10}\b and then attempt to parse the result as an int32, but you may not always have access to a parser (example text editor search/replace).

edited Dec 24, 2013 at 0:09

answered Dec 22, 2013 at 21:34

Pi Marillion

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2 Comments

Alan Moore Over a year ago

It's probably just a typo, but your last, "quick and dirty" regex starts with (?:-?|\b), which effectively makes both the minus sign and the word boundary optional. It should be either (?:-|\b) like in the first two regexes, or -?\b.

Pi Marillion Over a year ago

Right you are. Thanks for taking the time to read so thoroughly.

Collectives™ on Stack Overflow

Regexp only integer issue

4 Answers 4

***************

Regexp is not made for matching arbitrary range numbers.

***************

First, break into equal length ranges:

Second, break into ranges that yield simple regexes:

Turn each range into a regex:

Collapse adjacent powers of 10:

Combining the regexes above yields:

Next we'll try factoring out common prefixes using a tree:

Parse into tree based on regex prefixes:

Turning the parse tree into a regex yields:

We choose the shorter one as our result.

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Collectives™ on Stack Overflow

4 Answers 4

***************

Regexp is not made for matching arbitrary range numbers.

***************

First, break into equal length ranges:

Second, break into ranges that yield simple regexes:

Turn each range into a regex:

Collapse adjacent powers of 10:

Combining the regexes above yields:

Next we'll try factoring out common prefixes using a tree:

Parse into tree based on regex prefixes:

Turning the parse tree into a regex yields:

We choose the shorter one as our result.

Comments

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