Lists in Tcl - fundamentals in a commented source code example
Archive - Originally posted on "The Horse's Mouth" - 2013-11-16 14:22:18 - Graham EllisWhen 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
#Â in this example, we do NOT want to keep track of the position number
foreach person $party {
puts "Invite $person to the party"
}
# Here we are looping through each item of the list
#Â in this example, we DO want to keep track of the position number
for {set count 0} {$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!