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Regex

The Regex module is available via require "pluto:regex" and provides Soup's flavor of the popular string matching language.

regex.new​

Parses a pattern and creates an instance for it.

Parameters​

  1. The regex to be compiled. Note that this must be a full pattern with a start and end delimiter (commonly /). Flags may optionally be present after the end delimiter.

Returns​

A pattern instance.

regex.match​

Attempts to match a pattern instance.

Parameters​

  1. The pattern instance.

Returns​

A table with an index/key for each matching group or nil if no matches.

pluto
local regex = require "pluto:regex"
local pattern = new regex [[/^the (?:(.+) )?one$/]]
print(dumpvar(pattern:match("the one")))
--> {
-->     [0] = string(7) "the one",
--> }
print(dumpvar(pattern:match("the chosen one")))
--> {
-->     [1] = string(6) "chosen",
-->     [0] = string(14) "the chosen one",
--> }
print(pattern:match("not the one"))
--> nil

The overall pattern match is in index 0, and in this case there is only the 1 capturing group, that being (.+).

Capture group names will be used if available:

pluto
local regex = require "pluto:regex"
local pattern = new regex [[/^the (?:(?'what'.+) )?one$/]]
print(dumpvar(pattern:match("the chosen one")))
--> {
-->     [0] = string(14) "the chosen one",
-->     ["what"] = string(6) "chosen",
--> }

regex.search​

Looks for a match of the regex in a string.

Parameters​

  1. The pattern instance.
  2. The string to search in.
  3. The offset to start searching at. Defaults to 1.

Returns​

On success:

  1. The start offset.
  2. The end offset.

On failure: Nil.

pluto
local regex = require "pluto:regex"
local pattern = new regex [[/[A-Z]/]]
print(pattern:search("Hello World")) -- 1, 2
print(pattern:search("Hello World", 2)) -- 7, 8
print(pattern:search("Hello World", 8)) -- nil

regex.replace​

Replaces the first or all matches in a string, depending on the 'g' flag.

Parameters​

  1. The pattern instance.
  2. The string to search in.
  3. The replacement string.

Returns​

The new string.

Replace first match
pluto
local regex = require "pluto:regex"
local r = new regex [[/[0-9]+/]]
print(r:replace("I have 3 apples and 5 bananas.", "2")) --> I have 2 apples and 5 bananas.
Replace all matches
pluto
local regex = require "pluto:regex"
local r = new regex [[/[0-9]+/g]]
print(r:replace("I have 3 apples and 5 bananas.", "2")) --> I have 2 apples and 2 bananas.

regex.substitute​

Substitutes the first or all matches in a string, depending on the 'g' flag.

Parameters​

  1. The pattern instance.
  2. The string to search in.
  3. The substitution string. The substitution can reference capturing groups by their index, e.g. $1 for capturing group 1. Use $$ to produce $.

Returns​

The new string.

pluto
local regex = require "pluto:regex"
local r = new regex [[/.+ (.+)/]]
print(r:substitute("hello earth", "welcome to $1")) --> welcome to earth