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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.
Clean code, jump free (Example in Lua)

The "goto" statement - in languages that still support it - is regarded with disdain by Computer Scientists as it makes for spaghetti code - hard to follow and going all over the place!

In some ways, loop controls "break" and "continue" ("last", "next" and "redo" in Perl; "next", "redo", "retry" and "break" in Ruby) are also forms of the goto. They are not as bad in that they only jump within a limited area, but on the other hand many forms don't involve labels so that there's no clue at the destination point in your code that it's an arrival point.

Having slagged off these statements (and in reality I'm being a pedantic computer scientist by doing so - I use them personally from time to time!) I had better off you the alternative. Written on yesterday's Lua course as a demonstration - here's a while loop that has an ugly break in it ...

j=14
while 1 do
  print (j)
  if j > 20 then break end
  j = j + 1
end
print ("done")


... and here's the alternative using a control variable. ...

j=14
running = true
while running do
  print (j)
  if j > 20 then
    running = false
  else
    j = j + 1
  end
end
print ("done")


That code being longer, but purer and easier to maintain.
(written 2008-08-06, updated 2008-08-07)

 
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)
  [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)
  [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)

R104 - Ruby - Control Structures
  [960] 1st, 2nd, 3rd revisited in Ruby - (2006-12-02)
  [962] Breaking a loop - Ruby and other languages - (2006-12-03)
  [985] Equality in Ruby - == eql? and equal? - (2006-12-14)
  [995] Ruby's case - no break - (2006-12-17)
  [1163] A better alternative to cutting and pasting code - (2007-04-26)
  [1220] for loop - how it works (Perl, PHP, Java, C, etc) - (2007-06-06)
  [1582] Ruby, C, Java and more - getting out of loops - (2008-03-19)
  [1587] Some Ruby programming examples from our course - (2008-03-21)
  [1870] What to do with a huge crop of apples - (2008-11-04)
  [1887] Ruby Programming Course - Saturday and Sunday - (2008-11-16)
  [1891] Ruby to access web services - (2008-11-16)
  [1904] Ruby, Perl, Linux, MySQL - some training notes - (2008-11-23)
  [2287] Learning to program in Ruby - examples of the programming basics - (2009-07-15)
  [2471] A short form of if ... then ... else - (2009-10-23)
  [2619] Passing code to procedures and yield in Ruby - (2010-02-02)
  [2711] For loop - checked once, or evety time? Ruby v Perl comparison and contrast - (2010-04-07)
  [2892] Alternative loops and conditionals in Ruby and Perl - (2010-07-28)
  [2975] Why do I need brackets in Ruby ... or Perl, Python, C or Java - (2010-09-29)
  [3156] Splitting data reading code from data processing code - Ruby - (2011-02-04)
  [3158] Ruby training - some fresh examples for string handling applications - (2011-02-05)
  [3159] Returning multiple values from a function call in various languages - a comparison - (2011-02-06)
  [3200] How a for loop works Java, Perl and other languages - (2011-03-12)
  [3253] Is this number between? Does this list include? - Ruby - (2011-04-18)
  [3254] Multiple inputs, multiple out, ruby functions - (2011-04-19)
  [3422] Assigning values to variables within other statements - Ruby - (2011-09-07)
  [3619] Ruby v Perl - a comparison example - (2012-02-21)
  [3620] Finding the total, average, minimum and maximum in a program - (2012-02-22)
  [3769] Muttable v immutable and implications - Ruby - (2012-06-20)
  [4370] Conditionals, loops and methods in Ruby - a primer with simple examples - (2014-12-29)
  [4402] Finding sum, minimum, maximum and average in Python (and Ruby) - (2015-01-19)
  [4503] Separating your code for easier testing, understanding and re-use; example in Ruby - (2015-06-02)
  [4504] Where does Ruby load modules from, and how to load from current directory - (2015-06-03)
  [4674] Alternating valuses / flip-flop / toggle - example in Ruby - (2016-05-17)


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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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