CODEWITHSUNDEEP
phpregexpreg-replacepreg-match
Ilia Ross
Ilia Ross

Reputation: 13412

Regex for validating numbers preceding with two dashes (hyphens)

I got stuck with regexp to validate only numbers from 1-10 that could have two dashes(hyphens) before, for example:

--9

or

--10

or

--1

but not

--11 or not --0

I tried like seems to me everything, example:

/(-\-\[1-10])/

What is wrong?

EDIT 1:

Thanks a lot for so many working examples!!

What if I also wanted to validate to numbers before all of this, example:

8--10 but not 0--10 or not 11--11

I tried this but it didn't work:

/--([1-9]|10:[1-9]|10)\b/

EDIT 2:

Oh, this one works, finally:

/^(10|[1-9])--(10|[1-9])$/

Upvotes: 1

Views: 295

Answers (5)

Toto
Toto

Reputation: 91518

Have a try with:

/\b(?:[1-9]|10)--(?:[1-9]|10)\b/

Change according to OP's edit.

Explanation:

The regular expression:

(?-imsx:\b(?:[1-9]|10)--(?:[1-9]|10)\b)

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
----------------------------------------------------------------------
  (?:                      group, but do not capture:
----------------------------------------------------------------------
    [1-9]                    any character of: '1' to '9'
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    10                       '10'
----------------------------------------------------------------------
  )                        end of grouping
----------------------------------------------------------------------
  --                       '--'
----------------------------------------------------------------------
  (?:                      group, but do not capture:
----------------------------------------------------------------------
    [1-9]                    any character of: '1' to '9'
----------------------------------------------------------------------
   |                        OR
----------------------------------------------------------------------
    10                       '10'
----------------------------------------------------------------------
  )                        end of grouping
----------------------------------------------------------------------
  \b                       the boundary between a word char (\w) and
                           something that is not a word char
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

Upvotes: 3

Ravi K Thapliyal
Ravi K Thapliyal

Reputation: 51721

The correct regex is

/\b--([1-9]|10)\b/

You're incorrectly escaping the first [ of your character class as \[. The character class used is incorrect as well. It would be treated as a character class with members 1 to 1 and a 0 i.e. [10] which means it matches either 0 or 1.

Also, the hyphens - don't need to be escaped outside a character class []. To validate the numbers that come before the hyphens as well use

/\b([1-9]|10)--([1-9]|10)\b/

Upvotes: 2

ProgramFOX
ProgramFOX

Reputation: 6390

Outside a character class, you don't need to escape hyphens. Also, your character class [1-10] will only match 1 and 0, because [1-10] is equal to [10] and that will only match 1 and 0. Try this regex:

/^--(10|[1-9])$/

Upvotes: 2

vdubus
vdubus

Reputation: 456

When you write [1-10], it mean characters 1 to 1 + the 0 character. It as if you had write [0-1].

In fact, in your case, it would be better to test cases --1 to --9 and case --10 separately with something like : /^(--10)|(--[1-9])$/

You can test your regex on http://myregexp.com/

Upvotes: 1

Alma Do
Alma Do

Reputation: 37365

I guess this will fit

/\-\-([1-9]|10)\b/

if you don't want to capture your number, add ?: :

/\-\-(?:[1-9]|10)\b/

Upvotes: 2

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