Re: Regex - Ensure 0,1 occurrences from a list of possibilities

There are only 64 permutations. Not a pretty regex though:

"D-(1234|1243|1324|1342|1423|1432|2134|2143|2314|2341|2413|2431|
3124|3142|3214|3241|3412|3421|4123|4132|4213|4231|4312|4321|123|
124|132|134|142|143|213|214|231|234|241|243|312|314|321|324|341|342|
412|413|421|423|431|432|12|13|14|21|23|24|31|32|34|41|42|43|1|2|3|4)$"

-Mark

<nospam@invegat> wrote in message news:vb20t4pe3tgjj7gm8igql0dcl9ec36e52p@xxxxxxxxxx
By my calculation there are 504 possibilities, I wouldn't call that
"only a few". If I were doing it these way I would generate the
matching strings with a 1 time use program.

On Sun, 29 Mar 2009 23:33:45 +0000 (UTC), Jesse Houwing
<jesse.houwing@xxxxxxxxxxxxxxxx> wrote:

Hello Byron,

I'm looking for an expression that checks that within a string only
certain characters appear, and that they appear at most 1 time. For
example, a string can have up to 4 unique digits between 1 and 4.

The following strings should pass:
D-1
D-14
D-1234
D-41
The following should fail:
D- (no digit)
D-0 (out of range)
D-5 (out of range)
D-11 (repeated digit)
D-1 2 (embedded space)
D-12345 (out of range and too long)
The expression "D-[1234]{1,4}" comes close, but it matches even when a
digit is repeated within the string.

Any help would be greatly appreciated.

As there's only a few possibilities, you could write them out like this:

(1234|1324|1342|1423|1432|....4321)

And do the same with the other options.

A better wat woukd be to check the general format with a regex, and then
later (if you're using asp.net validators) check the other requirement.

There are other possibilities (as invegat pointed out), but those aren't
supported by clientside Javascript , which would require a serverside check
anyway.

.

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