/* REXX    DROPDUP    Eliminate duplicate lines in a dataset.
*/
address ISREDIT
'macro (parms)'
sw.0batch = Sysvar("SYSENV") = "BACK"
if sw.0batch then rc = Trace("R")
 
push parms; pull parms
sw.0quiet = Wordpos("QUIET",parms) > 0
sw.0disp  = Wordpos("DISP",parms) > 0
if sw.0disp then sw.0quiet = '1'
 
"(lmar rmar) = BOUNDS"
lp = Wordpos("LEN",parms); if lp > 0 then len = Word(parms,lp+1)
                                     else len = rmar
"F P'=' LAST"
"(lastline) = CURSOR"
"CURSOR = 1"
rc = 0
"(prev) = LINE 1"
do i = 1 to lastline-1
   j = i + 1
   if j > lastline then leave
   "(this) = LINE" j
   do while (Left(prev,len) = Left(this,len)) & rc = 0
      if sw.0disp then do; say "Nominally deleted: *"j"*" Strip(this)                  
         j = j + 1; i = i + 1; end
      else do
         "DELETE" j
         lastline = lastline - 1
         end
      if sw.0quiet      then nop; else,
         say "Deleted" j", Lastline now" lastline"."
      "(this) = LINE" j
   end
   prev = this
end /* i */
"CURSOR = 1 1"
if sw.0batch then "END"
exit                                   /*@ DROPDUP                   */