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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.
Tcl sandwich - lists in Tcl

In Tcl, a list is simply a string that's held in the same format (i.e. with the same delimiters and protection) as a series of parameters to a Tcl command. The split command (which does a great deal in languages such as Perl and PHP) really does little more than change the delimiters if need be, and add protective \ { and } characters - again only if need be.

Here's an example where we're splitting and manipulating the contents of a sandwich.

tcl>set sarnie "cheese, marmite, onion, pickle"
tcl>set d4 [split $sarnie ,]
tcl>set d4
cheese { marmite} { onion} { pickle}

At this point, the braces have been added to protect the space character which is part of the individual ingredient

tcl>foreach ingrid $d4 {
=>puts [string trim $ingrid]
=>}
cheese
marmite
onion
pickle

I used string trim to remove the space before printing each element out

Let's rejoin the ingredients into a string using the word "and" as the glue

tcl>set d5 [join $d4 " and "]
tcl>set d5
cheese and marmite and onion and pickle

or as an alternative, print it out sorted into the order of ingedients with my favourite first ;-)

tcl>lsort $d4
{ marmite} { onion} { pickle} cheese
tcl>
(written 2004-12-08, updated 2006-06-05)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
T206 - Tcl/Tk - Lists
  [463] Splitting the difference - (2005-10-13)
  [781] Tcl - lappend v concat - (2006-06-27)
  [1282] Stringing together Tcl scripts - (2007-07-29)
  [1283] Generating traffic for network testing - (2007-07-29)
  [1334] Stable sorting - Tcl, Perl and others - (2007-09-06)
  [1402] Tcl - append v lappend v concat - (2007-10-23)
  [1405] Sorting in Tcl - lists and arrays - (2007-10-24)
  [1601] Replacing the last comma with an and - (2008-04-04)
  [2468] What are Tcl lists? - (2009-10-22)
  [2472] split and join in tcl and expect - (2009-10-23)
  [3285] Extracting data from a string / line from file - Tcl - (2011-05-10)
  [3394] The difference between lists and strings - Tcl - (2011-08-16)
  [3415] User defined sorting and other uses of callbacks in Tcl and Tk - (2011-09-02)
  [3582] Tcl collections - lists, dicts and array - (2012-01-16)
  [3583] Expanding a list of parameters in Tcl - {*} and eval - (2012-01-17)
  [3618] lists and struct::list in Tcl - Introduction to struct::list and examples - (2012-02-18)
  [4209] Lists in Tcl - fundamentals in a commented source code example - (2013-11-16)
  [4454] Everything is a string - even a list - (2015-03-11)
  [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11)


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