:TITLE: More list commands - lsearch, lsort, lrange
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;# RCSID: $Header: /cvsroot/tcl/tcltutorial/original/Tcl16.lsn,v 1.1 2004/11/04 16:01:13 davidw Exp $
;# Copyright (c) 1995 Clif Flynt
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;# Dexter, MI 48130
;# clif@cflynt.com
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:LESSON_TEXT_START_LEVEL 0:
Lists can be searched with the lsearch command,
sorted with the lsort command, and a range of list entries can be
extracted with the lrange command.
- lsearch
list pattern
- searches list for an entry that matches pattern, and returns
the index for the first match, or a -1 if there is no match.
- lsort
list
- sorts list and returns a new list in the sorted order. By default,
it sorts the list into alphabetic order.
- lrange
list first last
- returns a list composed of the first through last entries
in the list. If first is less than or equal to 0, it is treated as the
first list element. If last is end or a value greater than the
number of elements in the list, it is treated as the end. If first is
greater than last then an empty list is returned.
By default, lsearch uses the globbing method of finding a match.
Globbing is the wildcarding technique that the shell uses.
:TEXT_END:
:LESSON_TEXT_START_LEVEL 1:
Lists can be searched with the lsearch command,
sorted with the lsort command, and a range of list entries can be
extracted with the lrange command.
- lsearch
list pattern
- searches list for an entry that matches pattern, and returns
the index for the first match, or a -1 if there is no match.
- lsort
list
- sorts list and returns a new list in the sorted order. By default,
it sorts the list into alphabetic order.
- lrange
list first last
- returns a list composed of the first through last entries
in the list. If first is less than or equal to 0, it is treated as the
first list element. If last is end or a value greater than the
number of elements in the list, it is treated as the end. If first is
greater than last then an empty list is returned.
By default, lsearch uses the globbing method of finding a match.
Globbing is the wildcarding technique that the shell uses.
globbing wildcards are:
- *
- Matches any quantity of any character
- ?
- Matches one occurrence of any character
- \X
- The backslash escapes a special character in globbing
just the way it does in Tcl substitutions. Using the backslash lets you use
glob to match a * or ?.
- [...]
- Matches one occurrence of any character within the brackets.
A range of characters can be matched by using a range between the brackets.
For example, [a-z] will match any lower case letter.
:TEXT_END:
:LESSON_TEXT_START_LEVEL 2:
There are several other operations which can be performed on a list.
Lists can be
- searched with the
lsearch command,
- sorted with the
lsort command,
- a range of list entries can be extracted with the
lrange command.
- lsearch
list pattern
- searches list for an entry that matches pattern, and returns
the index for the first match, or a -1 if there is no match.
- lsort
list
- sorts list and returns a new list in the sorted order. By default,
it sorts the list into alphabetic order.
- lrange
list first last
- returns a list composed of the first through last entries
in the list. If first is less than or equal to 0, it is treated as the
first list element. If last is end or a value greater than the
number of elements in the list, it is treated as the end. If first is
greater than last then an empty list is returned.
By default, lsearch uses the globbing method of finding a match.
Globbing is the wildcarding technique that the shell uses. The
globbing wildcards are:
- *
- Matches any quantity of any character
lsearch $list a* would return the index of the first
listitem that started with the letter 'a', regardless of what followed.
- ?
- Matches one occurrence of any character
lsearch $list a? would return the index of the first
listitem that started with the letter 'a', and had only one character
after the a.
- \X
- The backslash escapes a special character in globbing
just the way it does in Tcl substitutions. Using the backslash lets you use
glob to match a * or ?.
lsearch $list a\* would return the index of the first listitem that
started with the letter 'a', and had an asterisk after the 'a'.
- [...]
- Matches one occurrence of any character within the brackets.
A range of characters can be matched by using a range between the brackets.
For example, [a-z] will match any lower case letter.
lsearch $list [a-e]* would return the index of the
first listitem that started with a letter between 'a' and 'e'.
Run the example code. Try removing the * in the lsearch commands, and see
how that affects the output.
:TEXT_END:
:CODE_START:
set list [list {Washington 1789} {Adams 1797} {Jefferson 1801} \
{Madison 1809} {Monroe 1817} {Adams 1825} ]
set x [lsearch $list Washington*];
set y [lsearch $list Madison*];
incr x; incr y -1; ;# Set range to be not-inclusive
set subsetlist [lrange $list $x $y]
puts "The following presidents served between Washington and Madison"
foreach item $subsetlist {
puts "Starting in [lindex $item 1]: President [lindex $item 0] "
}
set x [lsearch $list Madison*]
set srtlist [lsort $list];
set y [lsearch $srtlist Madison*];
puts "\n$x Presidents came before Madison chronologically"
puts "$y Presidents came before Madison alphabetically"
:TEXT_END: