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Tcl - a great engineering language

tcl course, February 2011It might be a little old and out of fashion - but Tcl is still very much in use, we use it and we can offer you a learning to program in Tcl training course if you're new to programming, or a Tcl Programming course if you've programmed in another language before. We also offer a two day Tk course as a follow up if you're going to be using that GUI.

Tcl is a very stable language that's great for engineers and we quietly get a lot of web site traffic looking at the examples on our web site. It's because one of those examples bubbles up to over 50 accesses per day that I've been reminded just how important the language remains.

Here's part of that popular page: [full example]

if [expr $cost > 100] {
   set cost [expr $cost * 0.8]
   puts "SPECIAL Group ticket at $cost"
} elseif [expr $cost > 20] {
   set cost [expr $cost * 0.9]
   puts "Group ticket at $cost"
} else {
   puts "Total Price will be $cost"
   }


Although the code looks fairly conventional, Tcl is actually a command base language rather than an operator based one. And that means that in the code above, spaces and line breaks are significant. if is a command. It takes a minimum of two space separated parameters - in this case there's one in square brackets, and one in curly braces. The curly brace parameter lasts severla lines ...

There are five more parameters to if in this particular example - "elseif", a "[]" condition, a "{}" block, "else" and finally another "{}" block. You'll note that only the "{}" blocks carry on from line to line - normally a new line is teh end of a Tcl command, and that means that placing the "{" on the end of the first line (and preceded by a space) is vital.

I really enjoy working with Tcl / giving courses in the language. For sure, I do more training on the likes of Lua, Python, Ruby and PHP these days, but please get follow the course links or get in touch if you would like a Tcl course!

(written 2010-03-17, updated 2011-03-01)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
T050 - Tcl/Tk - Tcl, Tcl/Tk and Expect - General
  [4616] Still teaching Tcl in 2016? - (2016-01-06)
  [4460] Using Object Oriented Tcl and the Tk toolkit together - real life example - (2015-03-12)
  [4434] Public training courses - upcoming dates - (2015-02-21)
  [4206] Writing the perfect program in Tcl? - (2013-11-13)
  [3286] Should we cover expect and/or Tk on our public Tcl courses? - (2011-05-11)
  [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04)
  [2504] Learning to program in ... - (2009-11-15)
  [2474] Using Tcl and Expect to automate repetitive jobs - (2009-10-24)
  [2429] Tcl scripts / processes on a web server via CGI - (2009-09-27)

T203 - Tcl/Tk - Conditionals and Loops
  [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11)
  [4323] Learning to program - Loop statements such as while - (2014-11-22)
  [4322] Learning to Program - the conditional statement (if) - (2014-11-21)
  [3571] Comparing loop commands in Tcl - (2012-01-06)
  [3570] Trapping errors in Tcl - the safety net that catch provides - (2012-01-06)
  [3397] Does a for loop evaluate its end condition once, or on every iteration? - (2011-08-18)
  [3189] Tcl - the danger of square brackets in a while command - (2011-03-02)
  [2471] A short form of if ... then ... else - (2009-10-23)
  [2261] Tcl - nice and nasty - (2009-06-29)
  [1696] Saying NOT in Perl, PHP, Python, Lua ... - (2008-07-04)
  [1477] Decisions - small ones, or big ones? - (2007-12-18)
  [1401] Tcl - using [] or {} for conditions in an if (and while) - (2007-10-23)
  [210] Joining lists in Tcl. Indirect variables in Tcl. - (2005-02-12)


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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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