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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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))
Automatically initialising Lua variables the first time

In Lua, you need to initialise variables before you perform arithmetic on them, but you CAN test them (and if they don't exist, they will return false).

For example, this code initialises a variable to 0 if it doesn't exist, or takes its current value, then adds 1 to it straight away before saving it tack in the same variable.

callcounter = (callcounter or 0 ) +1

See that in use in full source code, within a function where it in effect becomes a static variable , here
(written 2009-08-10, updated 2009-08-12)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
U102 - Lua - Numbers and the Math library.
  [1699] If you are learning Lua, here are some more examples - (2008-07-06)
  [1744] Lua examples, Lua Courses - (2008-08-08)
  [2509] A life lesson from the accuracy of numbers in Excel and Lua - (2009-11-21)
  [3917] BODMAS - the order a computer evaluates arithmetic expressions - (2012-11-09)
  [4569] Lua - changes to how integers and floats are handled - 5.2 to 5.3 - (2015-11-02)


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Some other Articles
Businesses effected by road works in Melksham
Finding literals rather than patterns in Lua
Dot, dot, dot in Lua - variable length parameter lists
The indexed and hashed parts of a Lua table
Automatically initialising Lua variables the first time
Reading a data file and sensing EOF in Lua
World Flags in your PHP pages
Training Classes in other tongues
Koulutus, Open Source tietokone kielill[83][c2]ä
ldning, Open Source dator spr[83][c2]åk
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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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