Lua Requires Chilkat v11.1.0+

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

Lua

local chilkat = require("chilkat")

local success = false

local subject = "John Smith"
local pattern = "(?<first>\\w+)\\s+(?<last>\\w+)"

local sb = chilkat.StringBuilder.new()
sb:append(subject)

local json = chilkat.JsonObject.new()
json.emit_compact = false

local timeoutMs = 2000
local numMatches = sb:regex_match(pattern, json, timeoutMs)
if numMatches < 0 then
    -- Probably an error in the regular expression.
    -- Suggestion: Use AI to help create and/or diagnose regular expressions.
    print(sb.last_error_text)
    return
end

-- Examine the matches:
print(json: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:

json.i = json:int_of("named.first")
print("first: " .. json:string_of("match[0].group[i].cap"))

json.i = json:int_of("named.last")
print("last: " .. json:string_of("match[0].group[i].cap"))

-- Output is:

-- first: John
-- last: Smith