Tcl Built-In Commands lsort(1T)
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NAME
lsort - Sort the elements of a list
SYNOPSIS
lsort ?options? list
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DESCRIPTION
This command sorts the elements of list, returning a newlist in sorted order. The implementation of the lsort com-
mand uses the merge-sort algorithm which is a stable sort
that has O(n log n) performance characteristics. By default ASCII sorting is used with the result returned in increasing order. However, any of the following options may be specified before list to control the sorting process (unique abbreviations are accepted):-ascii Use string comparison with Unicode
code-point collation order (the name is
for backward-compatibility reasons.)
This is the default.-dictionary Use dictionary-style comparison. This
is the same as -ascii except (a) case is
ignored except as a tie-breaker and (b)
if two strings contain embedded numbers, the numbers compare as integers, notcharacters. For example, in -dictionary
mode, bigBoy sorts between bigbang and bigboy, and x10y sorts between x9y and x11y.-integer Convert list elements to integers and
use integer comparison.-real Convert list elements to floating-point
values and use floating comparison.-command command Use command as a comparison command. To
compare two elements, evaluate a Tcl script consisting of command with the two elements appended as additional arguments. The script should return an integer less than, equal to, or greater than zero if the first element is to be considered less than, equal to, or greater than the second, respectively. Tcl Last change: 8.3 1Tcl Built-In Commands lsort(1T)
-increasing Sort the list in increasing order
(``smallest'' items first). This is the default.-decreasing Sort the list in decreasing order
(``largest'' items first).-index index If this option is specified, each of the
elements of list must itself be a proper Tcl sublist. Instead of sorting basedon whole sublists, lsort will extract
the index'th element from each sublist and sort based on the given element. The keyword end is allowed for the index to sort on the last sublist element, and |end-index sorts on a sublist element |
offset from the end. For example,lsort -integer -index 1 {{First 24} {Second 18} {Third 30}}
returns {Second 18} {First 24} {Third 30}, and |lsort -index end-1 {{a 1 e i} {b 2 3 f g} {c 4 5 6 d h}}|
returns {c 4 5 6 d h} {a 1 e i} {b 2 3 f | g}. This option is much more efficientthan using -command to achieve the same
effect.-unique If this option is specified, then only
the last set of duplicate elements found in the list will be retained. Note that duplicates are determined relative to the comparison used in the sort. Thusif -index 0 is used, {1 a} and {1 b}
would be considered duplicates and only the second element, {1 b}, would be retained. NOTESThe options to lsort only control what sort of comparison is
used, and do not necessarily constrain what the values them-
selves actually are. This distinction is only noticeable when the list to be sorted has fewer than two elements.The lsort command is reentrant, meaning it is safe to use as
part of the implementation of a command used in the -command
option.EXAMPLES
Sorting a list using ASCII sorting:% lsort {a10 B2 b1 a1 a2}
B2 a1 a10 a2 b1 Tcl Last change: 8.3 2Tcl Built-In Commands lsort(1T)
Sorting a list using Dictionary sorting:% lsort -dictionary {a10 B2 b1 a1 a2}
a1 a2 a10 b1 B2 Sorting lists of integers:% lsort -integer {5 3 1 2 11 4}
1 2 3 4 5 11% lsort -integer {1 2 0x5 7 0 4 -1}
-1 0 1 2 4 0x5 7
Sorting lists of floating-point numbers:
% lsort -real {5 3 1 2 11 4}
1 2 3 4 5 11% lsort -real {.5 0.07e1 0.4 6e-1}
0.4 .5 6e-1 0.07e1
Sorting using indices:% # Note the space character before the c
% lsort {{a 5} { c 3} {b 4} {e 1} {d 2}}
{ c 3} {a 5} {b 4} {d 2} {e 1}% lsort -index 0 {{a 5} { c 3} {b 4} {e 1} {d 2}}
{a 5} {b 4} { c 3} {d 2} {e 1}% lsort -index 1 {{a 5} { c 3} {b 4} {e 1} {d 2}}
{e 1} {d 2} { c 3} {b 4} {a 5} Stripping duplicate values using sorting:% lsort -unique {a b c a b c a b c}
a b c More complex sorting using a comparison function:% proc compare {a b} {
set a0 [lindex $a 0]
set b0 [lindex $b 0]
if {$a0 < $b0} {
return -1
} elseif {$a0 > $b0} {
return 1 }return [string compare [lindex $a 1] [lindex $b 1]]
}% lsort -command compare \
{{3 apple} {0x2 carrot} {1 dingo} {2 banana}} {1 dingo} {2 banana} {0x2 carrot} {3 apple}SEE ALSO
list(1T), lappend(1T), lindex(1T), linsert(1T), llength(1T), | lsearch(1T), lset(1T), lrange(1T), lreplace(1T) KEYWORDS element, list, order, sort Tcl Last change: 8.3 3Tcl Built-In Commands lsort(1T)
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:_______________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
|____________________|__________________|_
| Availability | runtime/tcl-8 |
|____________________|__________________|_
| Interface Stability| Uncommitted ||____________________|_________________|
NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.3 4