Just another update

Task/Sorting-algorithms-Merge-sort/REXX/sorting-algorithms-merge-sort.rexx

@@ -1,63 +1,57 @@
-/*REXX program sorts a  (stemmed) array  using the  merge-sort  method. */
-call gen@                              /*generate the array elements.   */
-call show@ 'before sort'               /*show the before array elements.*/
-call mergeSort highItem                /*invoke the merge sort for array*/
-call show@ ' after sort'               /*show the  after array elements.*/
+/*REXX program sorts a (stemmed) array using the  merge─sort  algorithm.*/
+call gen@;             w=length(#)     /*generate an array (@.) of items*/
+call show@     'before sort'           /*show the before array elements.*/
+call mergeSort  #                      /*invoke the merge sort for array*/
+call show@     ' after sort'           /*show the  after array elements.*/
 exit                                   /*stick a fork in it, we're done.*/
 /*──────────────────────────────────GEN@ subroutine─────────────────────*/
-gen@:   @.=                            /*assign default value for @ stem*/
-@.1='---The seven deadly sins---'      /*everybody:  pick your favorite.*/
-@.2='==========================='
-@.3='pride'
-@.4='avarice'
-@.5='wrath'
-@.6='envy'
-@.7='gluttony'
-@.8='sloth'
-@.9='lust'
-           do highItem=1 while @.highItem\==''  /*find number of entries*/
-           end
-highItem=highItem-1                             /*adjust highItem by -1.*/
-return
-/*──────────────────────────────────MERGETO@ subroutine─────────────────*/
-mergeTo@: procedure expose @. !.;  parse arg L,n; if n==1 then return
-if n==2 then do;              h=L+1
-             if @.L>@.h  then do;   _=@.h;   @.h=@.L;   @.L=_;   end
-             return
-             end
-m=n%2
-call mergeTo@ L+m,n-m
-call mergeTo! L,m,1
-i=1;   j=L+m;         do k=L  while k<j
-                      if j==L+n | !.i<=@.j  then do;  @.k=!.i;  i=i+1; end
-                                            else do;  @.k=@.j;  j=j+1; end
-                      end   /*k*/
+gen@:           @.  =                  /*assign default value for @ stem*/
+                @.1 = '---The seven deadly sins---'   /*pick a favorite.*/
+                @.2 = '==========================='
+                @.3 = 'pride'
+                @.4 = 'avarice'
+                @.5 = 'wrath'
+                @.6 = 'envy'
+                @.7 = 'gluttony'
+                @.8 = 'sloth'
+                @.9 = 'lust'
+  do #=1  while @.#\==''; end;   #=#-1 /*find the number of entries in @*/
 return
 /*──────────────────────────────────MERGESORT subroutine────────────────*/
-mergeSort:  procedure expose @.;    call mergeTo@ 1,arg(1)
+mergeSort:  procedure expose @.;    call mergeTo@ 1,arg(1);         return
+/*──────────────────────────────────MERGETO@ subroutine─────────────────*/
+mergeTo@: procedure expose @. !.;   parse arg L,n ;   if n==1  then return
+if n==2  then do;   h=L+1              /*handle special case of 2 items.*/
+              if @.L>@.h  then do;   _=@.h;   @.h=@.L;   @.L=_;   end
+              return
+              end
+m=n%2                                  /*cut  N  in half  (integer div.)*/
+call mergeTo@ L+m,n-m                  /*divide items  to the left   ···*/
+call mergeTo! L,m,1                    /*   "     "     "  "  right  ···*/
+i=1;   j=L+m;           do k=L  while k<j     /*whilst items on right···*/
+                        if j==L+n | !.i<=@.j  then do; @.k=!.i; i=i+1; end
+                                              else do; @.k=@.j; j=j+1; end
+                        end   /*k*/
 return
 /*──────────────────────────────────MERGETO! subroutine─────────────────*/
-mergeTo!:   procedure expose @. !.;     parse arg L,n,_
-if n==1 then do;   !._=@.L;   return;   end
-if n==2 then do
-             h=L+1;      q=1+_
-             if @.L>@.h  then     do;   q=_;   _=q+1;   end
-             !._=@.L;    !.q=@.h
-             return
-             end
-m=n%2
-call mergeTo@ L,m
-call mergeTo! L+m,n-m,m+_
-i=L;   j=m+_
-                   do k=_  while k<j
-                   if j==n+_ | @.i<=!.j   then do;  !.k=@.i;  i=i+1;  end
-                                          else do;  !.k=!.j;  j=j+1;  end
-                   end   /*k*/
+mergeTo!:   procedure expose @. !.;      parse arg L,n,_
+if n==1  then do; !._=@.L; return; end /*handle special case of 1 item. */
+if n==2  then do                       /*   "      "      "   " 2 items.*/
+              h=L+1;      q=1+_
+              if @.L>@.h  then  do;   q=_;   _=q+1;   end
+              !._=@.L;    !.q=@.h
+              return                   /*done with special case of  N=2.*/
+              end
+m=n%2                                  /*cut  N  in half  (integer div).*/
+call mergeTo@ L,m                      /*divide items  to the left   ···*/
+call mergeTo! L+m,n-m,m+_              /*   "     "     "  "  right  ···*/
+i=L;   j=m+_;           do k=_  while k<j     /*whilst items on left ···*/
+                        if j==_+n | @.i<=!.j  then do; !.k=@.i; i=i+1; end
+                                              else do; !.k=!.j; j=j+1; end
+                        end   /*k*/
 return
 /*──────────────────────────────────SHOW@ subroutine────────────────────*/
-show@: widthH=length(highItem)         /*maximum the width of any line. */
-                      do j=1 for highItem
-                      say 'element' right(j,widthH) arg(1)':' @.j
-                      end   /*j*/
-say copies('─',60)                     /*show a seperator line (fence). */
+show@: say copies('▒',70);    do j=1  for #;  pad=left('',10)  /*indent.*/
+                              say pad  'element'  right(j,w) arg(1)':' @.j
+                              end   /*j*/
 return