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For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Lua Regular Expressions

OK - don't believe the headline - Lua doesn't support "Regular expressions" but it does have pattern matching. Why? Because Lua is designed to have a small footprint, and a conventional Regular Expression library would be 'bloat' - the pattern matching that's provided looks similar, and offers 80% of the facilities in 20% of the code. (See the 80 / 20 rule).

You'll find an example of Lua pattern matching here in our courseware examples. A Lua pattern is a string that may include:

• Literal Characters to match exactly - e.g.
Letters, digits and many special chars match exactly
%% means really match a % character (similar for other specials)

• Character groups to match any one character from a group - e.g.
[aeiou] for a lower case vowel
%d means a digit
%a for a letter
%u for an upper case letter
%l for a lower case letter
%s for a space
%S for a non-space (and other capitalisations for opposite groups)

• Anchors to say if you're looking at the start or end of a string - e.g.
^ means "starting with"
$ means "ending with"

• Counts to say how many times to match the previous character - e.g.
+ means one or more of the previous item
? means zero or 0ne character
* means 0 or more or the previous item
- also means 0 or more of the previous item but is SPARSE

• Capture parenthesis to indicate interesting bits to save

There are some examples of iterating through a string to match patterns in Lua here.

Lua's pattern matching is covered on both our Learning to Program in Lua and Lua Programming courses. Illustration - on a private Lua course

(written 2009-08-28, updated 2010-06-19)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
U108 - Lua - Pattern matching
  [1744] Lua examples, Lua Courses - (2008-08-08)
  [1847] Lua - IAQ (Infrequently Answered Questions) - (2008-10-18)
  [2702] First and last match with Regular Expressions - (2010-04-02)
  [2727] Making a Lua program run more than 10 times faster - (2010-04-16)
  [3687] Binary / bitwise operations in Lua with the standard bit32 library - (2012-04-06)
  [4366] Changing what operators do on objects - a comparison across different programming languages - (2014-12-26)


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