Visual FoxPro

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

Visual FoxPro

LOCAL lnSuccess
LOCAL lcSubject
LOCAL lcPattern
LOCAL loSb
LOCAL loJson
LOCAL lnTimeoutMs
LOCAL lnNumMatches
LOCAL lnFirstNameIdx
LOCAL lnLastNameIdx
LOCAL loSbTemp
LOCAL i

lnSuccess = 0

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

loSb = CreateObject('Chilkat.StringBuilder')
loSb.Append(lcSubject)

loJson = CreateObject('Chilkat.JsonObject')
loJson.EmitCompact = 0

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
    CANCEL
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('Chilkat.StringBuilder')

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.
lnSuccess = loSb.RegexReplace(loJson)
IF (lnSuccess = 0) THEN
    ? loSb.LastErrorText
    RELEASE loSb
    RELEASE loJson
    RELEASE loSbTemp
    CANCEL
ENDIF

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

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

RELEASE loSb
RELEASE loJson
RELEASE loSbTemp