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

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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 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, 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 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.

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

       lappend(n), lindex(n), linsert(n), list(n), llength(n), lrange(n), lreplace(n), lsearch(n)

KEYWORDS

       element, list, order, sort

Tcl									8.3								  lsort(n)