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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 Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own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))
The goto statement in Lua

In the past there was considerable debate in academia and industry on the merits of the use of goto statements, and indeed Lua didn't have them until release 5.2. Well used in Lua, they can provide an escape from inner loops, jumping to a label using a ::label:: format. For example:

  for z=1,10 do
     for y=1,10 do
        for x=1,10 do
           if x^2 + y^2 == z^2 then
              print('found a Pythagorean triple:', x, y, z)
              goto done
           end
        end
     end
  end
  ::done::


You cannot jump into an inner scope which includes local variables, and there are some further (sensible) limitations. This use of the goto to get out of multiple nested loops save you a whole series of nested checks or booleans.

There's a complete example showing sample output too [here].
(written 2012-04-06, updated 2012-04-07)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
U198 - New in Lua 5.2
  [3683] Weak references in Lua - what are they, and why use them? - (2012-04-04)
  [3687] Binary / bitwise operations in Lua with the standard bit32 library - (2012-04-06)
  [3690] Changes in Lua 5.2 - Garbage Collection - (2012-04-08)

U103 - Lua - Conditionals and loops
  [1685] Short circuit evaluation (lazy operator) in Lua - (2008-06-22)
  [1696] Saying NOT in Perl, PHP, Python, Lua ... - (2008-07-04)
  [1738] Clean code, jump free (Example in Lua) - (2008-08-06)
  [2351] Ternary operators alternatives - Perl and Lua lazy operators - (2009-08-12)
  [2454] For loops in Lua - (2009-10-14)
  [2455] Lua examples - coroutines, error handling, objects, etc - (2009-10-15)
  [3397] Does a for loop evaluate its end condition once, or on every iteration? - (2011-08-18)
  [3558] Python or Lua - which should I use / learn? - (2011-12-21)
  [4272] Lazy operators in Lua - what they mean, and examples - (2014-05-05)
  [4322] Learning to Program - the conditional statement (if) - (2014-11-21)
  [4323] Learning to program - Loop statements such as while - (2014-11-22)
  [4574] repeat until in Lua - a one or more rather than a zero or more loop - (2015-11-05)


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The goto statement in Lua
Programming Standards in Lua
Once upon a Maundy Thursday
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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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