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lsort(n)		     Tcl Built-In Commands		      lsort(n)

______________________________________________________________________________

NAME
       lsort - Sort the elements of a list

SYNOPSIS
       lsort ?options? list
_________________________________________________________________

DESCRIPTION
       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 char‐
       acteristics.

       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 col‐
			   lation order (the name is for  backward-compatabil‐
			   ity 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, not char‐
			   acters.   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 addi‐
			   tional 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,  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 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 rel‐
			   ative  to the comparison used in the sort.  Thus if
			   -index 0 is used, {1 a} and {1 b} would be  consid‐
			   ered 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.

EXAMPLES
       Sorting a list using ASCII sorting:
	      % lsort {a10 B2 b1 a1 a2}
	      B2 a1 a10 a2 b1

       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(n), lappend(n),  lindex(n),	 linsert(n),  llength(n),  lsearch(n), │
       lset(n), lrange(n), lreplace(n)

KEYWORDS
       element, list, order, sort

Tcl				      8.3			      lsort(n)
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