lsort

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)  perfor-
       mance 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, 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 argu-
                           ments.  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 key-
                           word 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}