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Lists in Tcl - fundamentals in a commented source code example

When I'm writing code demonstrations during class, they usually start off tidy and then get a bit scruffy as I add things in to answer delegate questions. For once last week, a Tcl list demonstration didn't get too untidy, so I give it you here with comments about what each few lines does.

  # different ways of setting up a list
  # (each of these contains three members)
  
  set party "{Ann Marie} Brenda Charles"
  set party "\"Ann Marie\" Brenda Charles"
  set party {"Ann Marie" Brenda Charles}
  set party "Ann\\ Marie Brenda Charles"
  set party {Ann\ Marie Brenda Charles}
  set party [list "Ann Marie" Brucella Charlie]
  
  # Append adds a string (so no space)
  # but lappend adds a list member (so spaced and protected)
  lappend party Brown
  lappend party Douggie
  
  puts $party
  # That prints:
  # {Ann Marie} Brucella CharlieBrown Douggie
  
  # How long is the "party" variable?
  puts [string length $party]
  puts [llength $party]
  # It's one list. Or a list with 4 indexed members. Or a string of 42 characters
  
  # What's the first item?
  set first [lindex $party 0]
  puts $first
  
  # What's the last item?
  set last [lindex $party [expr [llength $party] -1 ]]
  puts $last
  # surely there must be an easier way of doing that!
  set last [lindex $party end]
  puts $last
  
  # Here we are looping through each item of the list
  #[82] in this example, we do NOT want to keep track of the position number
  foreach person $party {
    puts "Invite $person to the party"
    }
  
  # Here we are looping through each item of the list
  #[82] in this example, we DO want to keep track of the position number
  for {set count 0} {$count < [llength $party]} {incr count} {
    set name [lindex $party $count]
    puts "I expect person $count will come (that's $name )"
    }


You can see sample output on the end of the code [here], and of course you can come on one of our courses to learn it yourself from me!
(written 2013-11-16, updated 2013-11-19)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
T206 - Tcl/Tk - Lists
  [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11)
  [4454] Everything is a string - even a list - (2015-03-11)
  [3618] lists and struct::list in Tcl - Introduction to struct::list and examples - (2012-02-18)
  [3583] Expanding a list of parameters in Tcl - {*} and eval - (2012-01-17)
  [3582] Tcl collections - lists, dicts and array - (2012-01-16)
  [3415] User defined sorting and other uses of callbacks in Tcl and Tk - (2011-09-02)
  [3394] The difference between lists and strings - Tcl - (2011-08-16)
  [3285] Extracting data from a string / line from file - Tcl - (2011-05-10)
  [2472] split and join in tcl and expect - (2009-10-23)
  [2468] What are Tcl lists? - (2009-10-22)
  [1601] Replacing the last comma with an and - (2008-04-04)
  [1405] Sorting in Tcl - lists and arrays - (2007-10-24)
  [1402] Tcl - append v lappend v concat - (2007-10-23)
  [1334] Stable sorting - Tcl, Perl and others - (2007-09-06)
  [1283] Generating traffic for network testing - (2007-07-29)
  [1282] Stringing together Tcl scripts - (2007-07-29)
  [781] Tcl - lappend v concat - (2006-06-27)
  [463] Splitting the difference - (2005-10-13)
  [144] Tcl sandwich - lists in Tcl - (2004-12-08)


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