Xbase++ Requires Chilkat v11.1.0+

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Xbase++

LOCAL nSuccess
LOCAL cSubject
LOCAL cPattern
LOCAL oSb
LOCAL oJson
LOCAL nTimeoutMs
LOCAL nNumMatches
LOCAL nFirstNameIdx
LOCAL nLastNameIdx
LOCAL oSbTemp
LOCAL i

nSuccess := 0

cSubject := "John Anders, +_+_+ Mary Robins $$$$"
cPattern := "(?<first>\w+)\s+(?<last>\w+)"

oSb := CreateObject("Chilkat.StringBuilder")
oSb:Append(cSubject)

oJson := CreateObject("Chilkat.JsonObject")
oJson:EmitCompact := 0

nTimeoutMs := 2000
nNumMatches := oSb:RegexMatch(cPattern, oJson, nTimeoutMs)
IF (nNumMatches < 0)
    //  Probably an error in the regular expression.
    //  Suggestion: Use AI to help create and/or diagnose regular expressions.
    ? oSb:LastErrorText
    oSb:destroy()
    oJson:destroy()
    RETURN
ENDIF

//  Examine the matches:
? oJson:Emit()

//  There are 2 matches:

//  {
//    "named": {
//      "first": 1,
//      "last": 2
//    },
//    "match": [
//      {
//        "group": [
//          {
//            "cap": "John Anders",
//            "idx": 0,
//            "len": 11
//          },
//          {
//            "cap": "John",
//            "idx": 0,
//            "len": 4
//          },
//          {
//            "cap": "Anders",
//            "idx": 5,
//            "len": 6
//          }
//        ]
//      },
//      {
//        "group": [
//          {
//            "cap": "Mary Robins",
//            "idx": 19,
//            "len": 11
//          },
//          {
//            "cap": "Mary",
//            "idx": 19,
//            "len": 4
//          },
//          {
//            "cap": "Robins",
//            "idx": 24,
//            "len": 6
//          }
//        ]
//      }
//    ]
//  }

//  To replace capture groups, write code to examine each capture group within
//  each match, and provide a replacement string.
//  Then call RegexReplace.

//  For example, let's capitalize the first names, and add append "on" to the last name.
//  After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

nFirstNameIdx := oJson:IntOf("named.first")
nLastNameIdx := oJson:IntOf("named.last")

oSbTemp := CreateObject("Chilkat.StringBuilder")

i := 0
nNumMatches := oJson:SizeOfArray("match")
DO WHILE i < nNumMatches

    oJson:I := i

    //  The replacement string for the first name will be all uppercase.
    oJson:J := nFirstNameIdx
    oSbTemp:Clear()
    oJson:StringOfSb("match[i].group[j].cap", oSbTemp)
    oSbTemp:ToUppercase()
    oJson:UpdateSb("match[i].group[j].rep", oSbTemp)

    //  Append "on" to the last name.
    oJson:J := nLastNameIdx
    oSbTemp:Clear()
    oJson:StringOfSb("match[i].group[j].cap", oSbTemp)
    oSbTemp:Append("on")
    oJson:UpdateSb("match[i].group[j].rep", oSbTemp)

    i := i + 1
ENDDO

//  The JSON now has replacement strings:
? oJson:Emit()

//  {
//    "named": {
//      "first": 1,
//      "last": 2
//    },
//    "match": [
//      {
//        "group": [
//          {
//            "cap": "John Anders",
//            "idx": 0,
//            "len": 11
//          },
//          {
//            "cap": "John",
//            "idx": 0,
//            "len": 4,
//            "rep": "JOHN"
//          },
//          {
//            "cap": "Anders",
//            "idx": 5,
//            "len": 6,
//            "rep": "Anderson"
//          }
//        ]
//      },
//      {
//        "group": [
//          {
//            "cap": "Mary Robins",
//            "idx": 19,
//            "len": 11
//          },
//          {
//            "cap": "Mary",
//            "idx": 19,
//            "len": 4,
//            "rep": "MARY"
//          },
//          {
//            "cap": "Robins",
//            "idx": 24,
//            "len": 6,
//            "rep": "Robinson"
//          }
//        ]
//      }
//    ]
//  }

//  Call RegexReplace to update the StringBuilder with the replacements.
nSuccess := oSb:RegexReplace(oJson)
IF (nSuccess == 0)
    ? oSb:LastErrorText
    oSb:destroy()
    oJson:destroy()
    oSbTemp:destroy()
    RETURN
ENDIF

? "Result after doing replacements:"
? oSb:GetAsString()

//  Result after doing replacements:
//  JOHN Anderson, +_+_+ MARY Robinson $$$$

oSb:destroy()
oJson:destroy()
oSbTemp:destroy()