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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
For loops in Lua

As an old Fortran programmer, I remember that a for loop was given a start point, an end point and a step ... and they had to be whole numbers (integers). Lua's for loops can be used that way, but they can be used a lot more flexibly too.

From, to, step for loops

Th egood news is that Lua works in double precision floats throughout, so your from, to and step can be anything you like ... and the step can go forwards or backwards. There's an example here where I report Celsius to Fahrenheit conversions - any step you like. You'll also notice that I have specified whole numbers for the conversion factors and they work ... 9 / 5 gives a result of 1.8 in Lua, not an integer result of 1.

If you're a C, Perl, PHP or Java programmer, you'll be used to for loops where the condition (end point) is checked every time around ... so that if the end condition is chanced within the loop, it effects the number of times that the loop runs. That's not the case with Lua which, like Fortran, decides the number of times the loop will run even before the first iteration is started. See here for an example.

in for loops

If you use an in style for loop, you're looping through an iteration (a set) of values or value pairs. Commonly used functions to generate these iterations are pairs which goes thought EVERY pair of values in a table, ipairs which only goes through the INDEXED pairs (i.e. it starts at element one, then gives elements 2, 3, etc until it finds a missing index at which point in stops, ignoring names elements and elements which are numbered but not in sequence from the start) and string.gmatch which goes though all strings that match a pattern within an incoming longer string.

See here for examples of pairs and ipairs, and here for an example of string.gfind
(written 2009-10-14, updated 2009-10-17)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
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)
  [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)
  [3686] The goto statement in Lua - (2012-04-06)
  [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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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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