For 2023 (and 2024 ...) - we are now fully retired from IT training. We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!
I am also active in many other area and still look after a lot of web sites - you can find an index ((here)) |
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
#[83] •[9a] in this example, we do NOT want to keep track of the position number
foreach person $party {
puts "Invite $person to the party"
}
# Here we are looping through each item of the list
#[83] •[9a] in this example, we DO want to keep track of the position number
for {set count 0} {$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 [144] Tcl sandwich - lists in Tcl - (2004-12-08) [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) [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)
Some other Articles
Formatting options in PythonPython functions - an introduction to how they workHandling JSON in Python (and a csv, marshall and pickle comparison)If elif elif elif - multiway selection in PythonLists in Tcl - fundamentals in a commented source code exampleTcl + Tk (Wish) - an introduction and revision exampleException handling in TclWriting the perfect program in Tcl?Regular Expression Substitution - TclWith the Shpigs and Donkeys
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This is a page archived from The Horse's Mouth at
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