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For 2023 - 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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))
Checking if the user has entered a number (Lua)

In Lua, there's a difference between 0 and nil - and that means that you can easily code to ask your user to enter a number, testing the result and allowing him to enter zero as a legitimate value. That may sound like it's no big deal, but you don't want a loop to exit on a premature 0.

Here's code to ask for a numeric response:
io.write("Please enter the age of your dog: ")
stuff = tonumber (io.read())
if stuff then

and you can be assured that the chunk will run even if a zero was entered, but will not run if a non-numeric value is given. [full source code]

That extends very easily into a loop if you need to keep asking until you get a number:
while not stuff do
  io.write("Please enter the age of your dog: ")
  stuff = tonumber (io.read())
  if not stuff then print ("Duh!") end

with this code relying on the non-existent variable stuff returning a false at initial entry to the loop. [full source of example]
(written 2009-08-13, updated 2009-08-14)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
U104 - Lua - Strings and the String library.
  [1744] Lua examples, Lua Courses - (2008-08-08)
  [2348] Finding literals rather than patterns in Lua - (2009-08-11)
  [2500] Dynamically formatting your results (Lua) - (2009-11-10)
  [4274] String formatting in Lua - string.format as a wrapper for sprintf - (2014-05-07)

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Geocoding - converting address to latitude / Longitude with PHP via Google
Error Handling in Lua with assert and pcall
A fresh example - objects the Lua way
Encapsulating shared code in a Lua module
Checking if the user has entered a number (Lua)
Passing multiple results back from a function - Lua, Python, etc
See this page in French
Training, Open Source computer languages
All change - Wiltshire Parliamentary
Printed Directories - the start of the updating season
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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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