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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.
Comparing loop commands in Tcl

Tcl offers you three different loop commands - here they are generating the same output:

while A condition is tested, and if true the commands in a loop are performed. The condition is then retested (provided that you have passed the test into while as a deferred block)

  set month 1
  while {$month <= 12} {
    puts "2. This is for month $month"
    incr month
    }


for A prettified version of while - it takes two extra parameters which are normally used to initialise a variable, and to increment that variable before the test is redone.

  for {set month 1} {$month <= 12} {incr month} {
    puts "1. This is for month $month"
    }


foreach Run a block of code (a loop) for each value in a list.

  foreach month {1 2 3 4 5 6 7 8 9 10 11 12} {
    puts "3. This is for month $month"
    }


The latter is significantly different in its use and intent.

See full program [here].

All loops taught / covered / compared on our Tcl and Tcl/Tk courses.
(written 2012-01-06)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
T203 - Tcl/Tk - Conditionals and Loops
  [210] Joining lists in Tcl. Indirect variables in Tcl. - (2005-02-12)
  [1401] Tcl - using [] or {} for conditions in an if (and while) - (2007-10-23)
  [1477] Decisions - small ones, or big ones? - (2007-12-18)
  [1696] Saying NOT in Perl, PHP, Python, Lua ... - (2008-07-04)
  [2261] Tcl - nice and nasty - (2009-06-29)
  [2471] A short form of if ... then ... else - (2009-10-23)
  [2681] Tcl - a great engineering language - (2010-03-17)
  [3189] Tcl - the danger of square brackets in a while command - (2011-03-02)
  [3397] Does a for loop evaluate its end condition once, or on every iteration? - (2011-08-18)
  [3570] Trapping errors in Tcl - the safety net that catch provides - (2012-01-06)
  [4322] Learning to Program - the conditional statement (if) - (2014-11-21)
  [4323] Learning to program - Loop statements such as while - (2014-11-22)
  [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11)


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Perl functions such as chop change their input parameters
New in Java 7 - and why we are not running public Java 7 courses
Adding Expect on top of Tcl - what is it and where can I get a training course to learn about it?
Comparing loop commands in Tcl
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First of the year
Initial thoughts - response to GW Rail Franchise Consultation for Wiltshire
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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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