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Reduce postcode regex length for United Kingdom (GB)

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
58/100
Issue type
Refactor
Clarity
Clearly specified
Activity status
Stale
Tech stack
cpp

Research direction

Search the repository for the GB postcode regex shown in the issue and read the surrounding address-validation code. Compare the existing and modified area groups, then run the nearest postcode or address-validation tests if available; done means the shorter expression preserves the existing accepted and rejected postcode cases.

Written by the indexing model from the issue text.

Description

The group that matches the postcode area can be grouped, reducing the overall regex length:

Original

Whole regex: GIR ?0AA|(?:(?:AB|AL|B|BA|BB|BD|BF|BH|BL|BN|BR|BS|BT|BX|CA|CB|CF|CH|CM|CO|CR|CT|CV|CW|DA|DD|DE|DG|DH|DL|DN|DT|DY|E|EC|EH|EN|EX|FK|FY|G|GL|GY|GU|HA|HD|HG|HP|HR|HS|HU|HX|IG|IM|IP|IV|JE|KA|KT|KW|KY|L|LA|LD|LE|LL|LN|LS|LU|M|ME|MK|ML|N|NE|NG|NN|NP|NR|NW|OL|OX|PA|PE|PH|PL|PO|PR|RG|RH|RM|S|SA|SE|SG|SK|SL|SM|SN|SO|SP|SR|SS|ST|SW|SY|TA|TD|TF|TN|TQ|TR|TS|TW|UB|W|WA|WC|WD|WF|WN|WR|WS|WV|YO|ZE)(?:\d[\dA-Z]? ?\d[ABD-HJLN-UW-Z]{2}))|BFPO ?\d{1,4}

Area group: (?:(?:AB|AL|B|BA|BB|BD|BF|BH|BL|BN|BR|BS|BT|BX|CA|CB|CF|CH|CM|CO|CR|CT|CV|CW|DA|DD|DE|DG|DH|DL|DN|DT|DY|E|EC|EH|EN|EX|FK|FY|G|GL|GY|GU|HA|HD|HG|HP|HR|HS|HU|HX|IG|IM|IP|IV|JE|KA|KT|KW|KY|L|LA|LD|LE|LL|LN|LS|LU|M|ME|MK|ML|N|NE|NG|NN|NP|NR|NW|OL|OX|PA|PE|PH|PL|PO|PR|RG|RH|RM|S|SA|SE|SG|SK|SL|SM|SN|SO|SP|SR|SS|ST|SW|SY|TA|TD|TF|TN|TQ|TR|TS|TW|UB|W|WA|WC|WD|WF|WN|WR|WS|WV|YO|ZE)

Modified regex

Whole regex: GIR ?0AA|(?:(?:A[BL]|B[ABDFHLNRSTX]?|C[ABFHMORTVW]|D[ADEGHLNTY]|E[CHNX]?|F[KY]|G[LYU]?|H[ADGPRSUX]|I[GMPV]|JE|K[ATWY]|L[ADELNSU]?|M[EKL]?|N[EGNPRW]?|O[LX]|P[AEHLOR]|R[GHM]|S[AEGK-PRSTWY]?|T[ADFNQRSW]|UB|W[ACDFNRSV]?|YO|ZE)(?:\d[\dA-Z]? ?\d[ABD-HJLN-UW-Z]{2}))|BFPO ?\d{1,4}

Area group: (?:A[BL]|B[ABDFHLNRSTX]?|C[ABFHMORTVW]|D[ADEGHLNTY]|E[CHNX]?|F[KY]|G[LYU]?|H[ADGPRSUX]|I[GMPV]|JE|K[ATWY]|L[ADELNSU]?|M[EKL]?|N[EGNPRW]?|O[LX]|P[AEHLOR]|R[GHM]|S[AEGK-PRSTWY]?|T[ADFNQRSW]|UB|W[ACDFNRSV]?|YO|ZE)

Dominant language
C++
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Forks
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