Emulating advanced regex features using Lua patterns and pure Lua code
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- Subject: Emulating advanced regex features using Lua patterns and pure Lua code
- From: Lorenzo Donati <lorenzodonatibz@...>
- Date: 2011年6月20日 12:12:32 +0200
Hi all!
A recent thread about Lua patterns not being regexes induced me to start
this thread.
I wonder if there are ways to EASILY emulate some advanced regex
features, usually found in PCRE-like packages, without resorting to LPEG
or C bindings to external libs.
For example, some uses of regex alternation can be emulated using
multiple calls to string.match and using logical operators, that is:
-- sort of pseudocode
local pcre = require 'pcre'
if pcre.match( haystack, "^foo|bar$" ) then ...
may be rewritten in pure Lua as:
if haystack:match "^foo$" or haystack:match "^bar$" then ...
Are there common Lua idioms to emulate advanced regex features as:
- Alternation (I don't know if the example above is universally applicable)
- Positive/Negative look-ahead/-behind
- Quantification/capture of complex patterns (as in pcre's "((?:foo)+)").
If there were a sort of one-to-one (almost boilerplate) translation
between those PCRE features and Lua idioms, it would very useful.
In particular, for my typical use case, I could reuse my knowledge of
PCRE without resorting to heavy external bindings or LPEG (I'm lazy,
I've got little time lately and it is still on my TODO list: "learn
LPEG" :-)
Thanks in advance for any suggestion/pointer or contribute to the
discussion (if the list find it worthwhile :-)
Cheers.
-- Lorenzo