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Pattern matching in Lua (not Regular Expressions)
Pattern matching example from a Well House Consultants training course
More on Pattern matching [link]

This example is described in the following article(s):
   • Lua examples, Lua Courses - [link]

Source code: iiapc Module: U108
--[[

Lua does NOT support regular expressions - or so they
say in the documentation. But the string patterns that
it matches are pretty darned close to regular expressions.

Here's an example that uses patterns to make a British
Postcode (one or two letters, one or two digits, space,
a digit and two letters. And occasionally the 2nd digit
in the first group is replaced by a letter!

]]


print ("stuff ...")
stuff = io.read()

itsere,ithink,fib,sib = string.find(stuff,
        "((%a%a?)%d[%a%d]?)%s+%d%a%a")

--[[ string.find returns ...
1. The start point of the match (or nil if no match)
2. The end point of the match
3. The First caputured part of the incoming string
   (If there are round brackets in the expression)
4. The second capured part ... and so on
]]


--[[
%a a letter
%a? perhaps another letter
%d a digit
[%a%d]? perhaps another digit or letter
%s+ one or more spaces
%d a digit
%a%a two letters

(...) to indicate 'interesting bits'

We could also have used ...
^ starts with
$ Ends at this point
... if we wanted to match a string that was JUST a postcode
]]


print (itsere) -- starts at
print (ithink) -- ends at
print (fib) -- first interesting bit
print (sib) -- second interesting bit

--[[ ==== Sample Output ========

[trainee@easterton al]$ lua iiapc
stuff ...
SN12 7NY
1
8
SN12
SN
[trainee@easterton al]$ lua iiapc
stuff ...
404, The Spa, Melksham, SN12 6QL, UK
25
32
SN12
SN
[trainee@easterton al]$

]]

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Lua
 * Lua Programming
 * Lua Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Lua are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Pattern matching" training module. You'll find a description of the topic and some other closely related examples on the "Pattern matching" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Web site author
This web site is written and maintained by Well House Consultants.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

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