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huecker.com # Grundlagen der Programmierung | Tcl Tutorial. -- |
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Often you will want to loop through the contents of an associative array - without having to specify the elements explicitly. For this the array names and array get commands are very useful. With both you can give a (glob-style) pattern to select what elements you need: foreach name [array names mydata] {
# Get names and values directly foreach {name value} [array get mydata] {
Note, however, that the elements will not be returned in any predictable order: this has to do with the underlying "hash table". If you want a particular ordering (alphabetical for instance), use code like: foreach name [lsort [array names mydata]] {
While arrays are great as a storage facility for some purposes, they are a bit tricky when you pass them to a procedure: they are actually collections of variables. This will not work: proc print12 {a} {
set array(1) "A"
print12 $array The reason is very simple: an array does not have a value. Instead the above code should be: proc print12 {array} {
set array(1) "A"
print12 array So, instead of passing a "value" for the array, you pass the name. This gets aliased (via the upvar command) to a local variable (that behaves the as original array). You can make changes to the original array in this way too. -- . Example .
# The example of the previous lesson revisited - to get a
# more general "database".
proc addname {db first last} {
upvar $db name
# Create a new ID (stored in the name array too for easy access).
incr name(ID)
set id $name(ID)
set name($id,first) $first ;# The index is simply a string!
set name($id,last) $last ;# So we can use both fixed and
;# varying parts.
}
proc report {db} {
upvar $db name
# Loop over the last names: make a map from last name to ID.
foreach n [array names name "*,last"] {
# Split the name to get the ID - the first part of the name!
regexp {^[^,]+} $n id
# Store in a temporary array:
# an "inverse" map of last name to ID.
set last $name($n)
set tmp($last) $id
}
# Now we can easily print the names in the order we want!
foreach last [lsort [array names tmp]] {
set id $tmp($last)
puts "$name($id,first) $name($id,last)"
}
}
# Initialise the array and add a few names.
set fictional_name(ID) 0
set historical_name(ID) 0
addname fictional_name Mary Poppins
addname fictional_name Uriah Heep
addname fictional_name Frodo Baggins
addname historical_name Rene Descartes
addname historical_name Richard Lionheart
addname historical_name Leonardo "da Vinci"
addname historical_name Charles Baudelaire
addname historical_name Julius Caesar
# Some simple reporting
puts "Fictional characters:"
report fictional_name
puts "Historical characters:"
report historical_name
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