Re: [Boost-users] Regex failing to match postcodes

From: Joshua B. Smith (josh_at_[hidden])
Date: 2004-06-14 10:36:30

On Mon, Jun 14, 2004 at 10:00:55AM +0100, James Gunn wrote:
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> 
> 
> Hi all,
> 
> I'm having some difficulty getting my regular expression working.
> Basically, I need to make sure that a UK postcode is valid. 
> The postcode that is passed to my function sometimes has extra things with
> it such as:
> 
> Wakefield, WF1 3RD
> Shrewsbury SY2 5PT Shropshire

Given that you've got messy data, have you considered matching everything
that might be a valid post code and then checking that against a symbol
table? 

That would reduce the complexity of your regex a lot.

You could also Spirit, though the learning curve on that is a bit 
steep.

> It now seems to be failing to find the postcode in the above examples.
> Also, when I pass my function a postcode that I know is invalid, such as JG2
> 7L5 it matches it as G2 7L5 instead of failing to do the match.

However, part of the problem with your regex is that J only matches if it
is with JE (it's between I[GMPV] and K[ATWY])

Hope this helps.  Here is the changed regex:

--- cut ---
 
 (?:(?:(^|\s)+
 A[BL]|B[ABDHLNRST]?| C[ABFHMORTVW]|D[ADEGHLNTY]|E[CHNX]?|F[KY]|G[LUY]?|
 H[ADGPRSUX]|I[GMPV]|J[GE]|K[ATWY]|L[ADELNSU]?|M[EKL]?|
 N[EGNPRW]?|O[LX]|P[AEHLOR]|R[GHM]|S[AEGKLMNOPRSTWY]?|
 T[0ADFNQRSW]|UB|W[ACDFNRSV]?|YO|ZE)
 \d(?:\d|[A-Z])?\s+\d[A-Z]{2}($|\s)+)

--- cut ---

-jbs

> 
> The regular expression I'm using is below:
> 
> (?:(?:(^|\s)+
> A[BL]|B[ABDHLNRST]?| C[ABFHMORTVW]|D[ADEGHLNTY]|E[CHNX]?|F[KY]|G[LUY]?|
> H[ADGPRSUX]|I[GMPV]|JE|K[ATWY]|L[ADELNSU]?|M[EKL]?|
> N[EGNPRW]?|O[LX]|P[AEHLOR]|R[GHM]|S[AEGKLMNOPRSTWY]?|
> T[0ADFNQRSW]|UB|W[ACDFNRSV]?|YO|ZE)
> \d(?:\d|[A-Z])?\s+\d[A-Z]{2}($|\s)+)
> 
> Can anyone tell me whats wrong with my expression? 
> BTW I'm using boost 1.31.0 on VC++ 7.1, Windows XP.