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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.
Lua - Table elements v table as a whole

Lua ... If you refer to a table name WITHOUT square brackets, you are referring to (and will effect) the whole table ... but if you refer to a table name and put something thereafter in square brackets, you are referring to just one element of the table. Actually, an almost identical story applies to other languages!

-- Whole table - no square brackets
 
people = {"Graham","Sadhana","Damien",'Ricardo',"Vanessa",'Thom'}
 
-- Just individual elements - with square brackets
 
people[7] = "Mandy"
people["Builder"] = "Bob"


Also in Lua ... if you use a for loop up to #people, or the ipairs function, you'll only loop through the consecutive elements of a table that are numbered from 1. If you use pairs instead, you'll select ALL the elements (and you can also do that with the next iterator.

print ("** This will list out until a missing index")
for k=1,#people do
  print (people[k])
end
  
print ("** print out all pairs")
for ping,pong in pairs(people) do
  print (pong,ping)
end
  
print ("** print out indexed pairs")
print ("** so it misses out named ones!")
print ("** Only gives the ones with index no.s!")
for ping,pong in ipairs(people) do
  print (pong,ping)
end


Here are the outputs from those two pieces of simple Lua code using tables run straight after each other:

** This will list out until a missing index
Graham
Sadhana
Damien
Ricardo
Vanessa
Thom
Mandy
** print out all pairs
Graham 1
Sadhana 2
Damien 3
Ricardo 4
Vanessa 5
Thom 6
Mandy 7
Bob Builder
** print out indexed pairs
** so it misses out named ones!
** Only gives the ones with index no.s!
Graham 1
Sadhana 2
Damien 3
Ricardo 4
Vanessa 5
Thom 6
Mandy 7
[trainee@easterton al]$


See here for more Lua resources - the page is a description of our course and if you click on the individual module details you'll be taken to resources specific to that particular modules - lots more examples, short articles such as this indexed by topic, etc
(written 2008-08-07)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
U105 - Lua - Tables and the table library.
  [1697] Sorting in lua - specifying your own sort routine - (2008-07-05)
  [2346] The indexed and hashed parts of a Lua table - (2009-08-10)
  [2499] ourdog is Greyhound, Staffie and Ginger Cake - (2009-11-09)
  [2699] Lua tables - they are everything - (2010-03-30)
  [2703] Lua Metatables - (2010-04-02)
  [3694] Special __ methods you can use in Lua metatables - (2012-04-12)
  [3725] Lua Tables - (2012-05-10)
  [4248] Metatables, Metamethods, classes and objects in Lua - (2014-03-18)
  [4273] Dot or Colon separator between table name and member in Lua - what is the difference? - (2014-05-06)
  [4571] Lua - using modules to add your own utilities - (2015-11-04)


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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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