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       lsort - Sort the elements of a list


       lsort ?options? list


       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  Unicode  code-point collation order (the name is for
              backward-compatibility reasons.)  This is the default.

              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.

              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.

              Sort the list in increasing order (“smallest”items first).  This is the default.

              Sort the list in decreasing order (“largest”items first).

              Return  a  list  of  indices  into  list  in  sorted  order  instead  of the values

       -index indexList
              If this option is specified, each of the elements of list must itself be  a  proper
              Tcl  sublist (unless -stride is used).  Instead of sorting based on whole sublists,
              lsort will extract the indexList'th element from each sublist (as  if  the  overall
              element  and  the  indexList  were  passed  to  lindex) and sort based on the given
              element.  For example,

                     lsort -integer -index 1 \
                           {{First 24} {Second 18} {Third 30}}

              returns {Second 18} {First 24} {Third 30},

                     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}, and

                     lsort -index {0 1} {
                         {{b i g} 12345}
                         {{d e m o} 34512}
                         {{c o d e} 54321}

              returns {{d e m o} 34512} {{b i g} 12345} {{c o d e} 54321} (because e sorts before
              i which sorts before o.)  This option is much more efficient than using -command to
              achieve the same effect.

       -stride strideLength
              If this option is specified, the  list  is  treated  as  consisting  of  groups  of
              strideLength  elements  and the groups are sorted by either their first element or,
              if the -index option is used, by the element within each group given by  the  first
              index passed to -index (which is then ignored by -index). Elements always remain in
              the same position within their group.

              The list length must be an integer multiple of strideLength, which in turn must  be
              at least 2.

              For example,

                     lsort -stride 2 {carrot 10 apple 50 banana 25}

              returns “apple 50 banana 25 carrot 10”, and

                     lsort -stride 2 -index 1 -integer {carrot 10 apple 50 banana 25}

              returns “carrot 10 banana 25 apple 50”.

              Causes  comparisons  to  be handled in a case-insensitive manner.  Has no effect if
              combined with the -dictionary, -integer, or -real options.

              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.


       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.


       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}

       Sorting a dictionary:                                                                      │

              % set d [dict create c d a b h i f g c e]                                           │
              c e a b h i f g                                                                     │
              % lsort -stride 2 $d                                                                │
              a b c e f g h i                                                                     │

       Sorting using striding and multiple indices:                                               │

              % # Note the first index value is relative to the group                             │
              % lsort -stride 3 -index {0 1} \                                                    │
                   {{Bob Smith} 25 Audi {Jane Doe} 40 Ford}                                       │
              {{Jane Doe} 40 Ford {Bob Smith} 25 Audi}                                            │

       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}


       list(3tcl),  lappend(3tcl),  lindex(3tcl),  linsert(3tcl),  llength(3tcl),  lsearch(3tcl),
       lset(3tcl), lrange(3tcl), lreplace(3tcl)


       element, list, order, sort