if 0 {[Richard Suchenwirth] 2004-08-27 - In the [Tcl chatroom], [JPS] discussed an extension to [lsort] which returns a list of indices in sorted order. This will go into a TIP, but for now here's a pure-Tcl implementation as proposed by James:
}
 proc lsort-indices list {
    if [llength $list] {
       set i -1
       foreach e $list {lappend tmp [list [incr i] $e]}
       foreach e [lsort -index 1 $tmp] {lappend res [lindex $e 0]}
       set res
    }
 }
if 0 {Testing:

 % lsort-indices {c b a}
 2 1 0
 % lsort-indices {}

 % lsort-indices {a a a}
 0 1 2

[RS] removed the initialisations of ''tmp'' and ''res'', but then had to guard the body with a one-armed [if] - it implies "else {}", which is the correct return value for an empty list.
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[Additional list functions] | [Arts and crafts of Tcl-Tk programming]
}