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Tcl - nice and nasty

Tcl is a lovely engineers language ... but goodness you can do some nasty things with it, and write some unmaintainable code.

set count 1
foreach type {if while} {
  $type {$count < 5} {
    puts "yay $type $count"
    incr count
  }
}


Which runs as follows:

earth-wind-and-fire:~ grahamellis$ tclsh tty
yay if 1
yay while 2
yay while 3
yay while 4
earth-wind-and-fire:~


A sign of a pure interpretative language ... the code changing from an if to a while as it runs. Is this:
a) An example of how you should NOT write code
b) An example of polymorphism when you least expect it
c) A feature looking for a benefit
d) All three of the above
And the answer is, of course, (d)
(written 2009-06-29, updated 2009-06-30)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
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)
  [2681] Tcl - a great engineering language - (2010-03-17)
  [2471] A short form of if ... then ... else - (2009-10-23)
  [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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