Lianja

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

Lianja

llSuccess = .F.

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

loSb = createobject("CkStringBuilder")
loSb.Append(lcSubject)

loJson = createobject("CkJsonObject")
loJson.EmitCompact = .F.

lnTimeoutMs = 2000
lnNumMatches = loSb.RegexMatch(lcPattern,loJson,lnTimeoutMs)
if (lnNumMatches < 0) then
    // Probably an error in the regular expression.
    // Suggestion: Use AI to help create and/or diagnose regular expressions.
    ? loSb.LastErrorText
    release loSb
    release loJson
    return
endif

// Examine the matches:
? loJson.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 $$$$

lnFirstNameIdx = loJson.IntOf("named.first")
lnLastNameIdx = loJson.IntOf("named.last")

loSbTemp = createobject("CkStringBuilder")

i = 0
lnNumMatches = loJson.SizeOfArray("match")
do while i < lnNumMatches

    loJson.I = i

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

    // Append "on" to the last name.
    loJson.J = lnLastNameIdx
    loSbTemp.Clear()
    loJson.StringOfSb("match[i].group[j].cap",loSbTemp)
    loSbTemp.Append("on")
    loJson.UpdateSb("match[i].group[j].rep",loSbTemp)

    i = i + 1
enddo

// The JSON now has replacement strings:
? loJson.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.
llSuccess = loSb.RegexReplace(loJson)
if (llSuccess = .F.) then
    ? loSb.LastErrorText
    release loSb
    release loJson
    release loSbTemp
    return
endif

? "Result after doing replacements:"
? loSb.GetAsString()

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


release loSb
release loJson
release loSbTemp