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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]
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
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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.
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