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Fork of Lua 5.3's pattern matching library with some added features.


luarocks install matchext


The complete pattern-matching facilities are not described here; for that, see the official Lua 5.3 reference manual "String Manipulation" section, specifically the functions find, match, gmatch, and gsub, and the "Patterns" sub-section. This library provides those same four functions with the same signatures and with all of the same behavior except for the added feature(s) listed below; additionally, the library provides extra functions, which are described in full below.

Additional features in the four basic functions

Balanced pattern with escape (%Bxyz)

The pattern token %Bxyz acts like the stock %bxz, matching a balanced pair of the opening character x and the closing character z, but adds the feature of the middle character y acting as an escape character, where each instance of y in the source string causes the next character in the source string to be skipped. Thus, %B(%) will match (foo%)bar) in test(foo%)bar)baz. As seen in this example, all three arguments to the %B token are interpreted raw; that is, all three represent themselves and do not carry any of the special meanings normally associated with them in pattern matching. (The same is true of the two arguments to the stock %b token.)

Extra functions

matchext.tmatch(s, pattern [, init])

Behaves the same as matchext.match(), but on a successful match, returns a table. This table contains any captures as a sequence (each at the index matching the order of returns from the stock match()), plus the entire match at index 0. Fields startpos and endpos are each a subtable containing the start and end positions, respectively, for each capture (the start and end position for a position capture is simply the value of that capture), as well as for the entire match at index 0. The table also contains the fields source, which contains the string over which the match was performed, and pattern, which contains the pattern used to perform the match. The table has one method, :expand(repl), which performs gsub-style expansion of repl (which must be a string) based on the captures in the table.

matchext.tgmatch(s, pattern)

Behaves the same as matchext.gmatch(), but on each iteration, produces a single table, which is the same as the table described for matchext.tmatch() above.

matchext.tgsub(s, pattern, repl [, n])

Behaves the same as matchext.gsub() unless repl is a function. In that case, the repl function receives just a single argument, which is the table described for matchext.tmatch() above. If repl is a string or table, then it behaves exactly the same as matchext.gsub(), and you should probably use that instead.


Given a string s, returns a new string that is a copy of s, but with all ASCII characters that are not alphanumeric and are not control codes escaped. The returned string can be plugged into any pattern and will match exactly s.


require 'matchext' does not touch the standard library's string table; it simply returns a table of its own functions, like a well-behaved Lua library should. For those who want to use this library's functions as methods of strings, or who otherwise want to get their hands dirty, running monkeypatch will take all of this library's functions except itself and insert them into the string table. It will also create a subtable at string.original, into which the stock find, match, gmatch, and gsub functions will be moved to preserve them (although they will no longer be usable as methods).


As a fork of the MIT-licensed Lua core, this library is also licensed under the MIT license. See the LICENSE file for more details.


Fork of Lua 5.3 pattern matching with added features







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