This command sorts the elements of list, returning a new
list in sorted order. The implementation of the lsort command
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 ASCII collation order. 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,
not characters. 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.
-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 based on 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. For example,
returns {Second 18} {First 24} {Third 30}.
This option is much more efficient than 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. Thus if
-index 0 is used, {1 a} and {1 b} would be
considered duplicates and only the second element, {1 b}, would
be retained.
NOTES
The options to lsort only control what sort of comparison is
used, and do not necessarily constrain what the values themselves
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.