Visual FoxPro

Regular Expression with Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups.

See the sample code below.

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

In PCRE2, named capture groups allow you to assign a name to a capturing group, making it easier to reference by name instead of number.

Syntax

(?<name>pattern)

or

(?'name'pattern)

Example

(?<first>\w+)\s+(?<last>\w+)

Applied to:

"John Smith"

Produces:

• first: John
• last: Smith

Visual FoxPro

LOCAL lnSuccess
LOCAL lcSubject
LOCAL lcPattern
LOCAL loSb
LOCAL loJson
LOCAL lnTimeoutMs
LOCAL lnNumMatches

lnSuccess = 0

lcSubject = "John Smith"
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()

* Here is the JSON showing the matches.
* Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

* {
*   "named": {
*     "first": 1,
*     "last": 2
*   },
*   "match": [
*     {
*       "group": [
*         {
*           "cap": "John Smith",
*           "idx": 0,
*           "len": 10
*         },
*         {
*           "cap": "John",
*           "idx": 0,
*           "len": 4
*         },
*         {
*           "cap": "Smith",
*           "idx": 5,
*           "len": 5
*         }
*       ]
*     }
*   ]
* }

* The capture group index is obtained by looking up the name in the JSON result.
* For example:

loJson.I = loJson.IntOf("named.first")
? "first: " + loJson.StringOf("match[0].group[i].cap")

loJson.I = loJson.IntOf("named.last")
? "last: " + loJson.StringOf("match[0].group[i].cap")

* Output is: 

* first: John
* last: Smith

RELEASE loSb
RELEASE loJson