if 0 {
<<TOC>>
----

**Introduction**
[MiHa] 2015-06-13: 
HelloWorld-programs are supposed to be the most simple, working programs of a given language.

But I want to extend such a HelloWorld-program to a one-page - reference-card, <<br>>
where all the essential features of the language are shown. <<br>>
Several short programs would be ok, too. <<br>>
If possible, while doing something useful (and/or funny).

Tcl by itself (without Tk) is http://wiki.tcl.tk/10259%|%quite simple%|%, 
so an amount of code to fill about one printed page should be enough. <<br>>
(The layout may need to be tweaked, e.g. printing front and back, landscape, and in 2-4 columns:)

Basic [Tcl Commands] to cover:
   * http://wiki.tcl.tk/1669%|%Comments%|% / statements
   * Output: [puts] / -nonewline
   ** [format]
   * Numeric [variable]s: [set]
   * multiple statements / assignments in one line
   ** simple calculations: [incr] / [expr]
   * [proc] / [return] - for functions
   * basic flowcontrol:
   ** [if] / then / else / elseif / comparing
   ** [for] - loop,  maybe also the [while]-loop / [break] / [continue]
   * [foreach]
   * String variables / quoting 
   * [exit]

Advanced features (to include if space permits):
   * input: [gets], [eof], [scan] / checking the input <<br>>This is an important topic, but likely too much for one page.
   * [catch]
   * [global] / $::var
   * [string]-operations (e.g. find/extract/replace char in a string, append, delete/split ...)
   * [data structure]s: 
   ** [array] / [parray]
   ** [list] / [lassign], [lappend], [lset], [linsert], [lreplace] / [lindex], [llength] / [lrange], [lsearch], [lsort]
   ** [dict]
   * [file]-operations / [open], [close ] / [glob]

...

More features, to be left out, for a later lesson (too advanced, or too rarely needed for an introduction):
   * [upvar] / [uplevel]
   * [namespace]s
   * [eval]
   * [interp]
   * [lambda]
   * [regexp] - this is very likely too complex to cover as just one small example on a general introduction page.
   * [switch]
   * [unknown]
...

Things to be aware of:
   * comments are commands, so quotes and braces inside need to be balanced
   * when to use / not to use "$" with variablenames ( set i 1; puts $i; incr i $i )

Maybe there already are some programs here in the wiki 
that would qualify for such a refcard-program...

}
----
**Program 1**
======tcl
  # HelloWorld001.tcl - 2015-06-13 - http://wiki.tcl.tk/41268
  # Output string to terminal:

  puts "Hello, World!"

  ### EOF ###
======

Some ideas:
   * Table of primes
   * Dice-rolling
   ** with min/max/average
   * Calculate distance
   * Number of days between dates
...


**Program 2**
======tcl
 # HelloWorld002.tcl - MiHa - 2015-06-13
 # http://wiki.tcl.tk/41268

 # http://ideone.com/xxx
  puts "Demo:"
  set i 0
  foreach s { Hello , world ! }  { incr i; puts "$i $s" }
 ### EOF ###
======

----
**Output**
======none
Demo:
1 Hello
2 ,
3 World
4 !
======

----
**Remarks**
This is the Alpha-version, there ''will'' be bugs,
so use with caution <<br>>
...

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'''See also:'''
   * http://wiki.tcl.tk/41210%|%ClockDemo%|%
   * ...

   
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