Data commit

Task/Closest-pair-problem/REXX/closest-pair-problem.rexx

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+/*REXX program  solves the   closest pair   of  points  problem  (in two dimensions).   */
+parse arg N LO HI seed .                         /*obtain optional arguments from the CL*/
+if  N=='' |  N==","  then  N=   100              /*Not specified?  Then use the default.*/
+if LO=='' | LO==","  then LO=     0              /* "      "         "   "   "     "    */
+if HI=='' | HI==","  then HI= 20000              /* "      "         "   "   "     "    */
+if datatype(seed, 'W')   then call random ,,seed /*seed for RANDOM (BIF)  repeatability.*/
+w= length(HI);     w= w + (w//2==0)              /*W:   for aligning the output columns.*/
+
+   /*╔══════════════════════╗*/      do j=1  for N            /*generate N random points*/
+   /*║ generate  N  points. ║*/      @x.j= random(LO, HI)     /*    "    a    "     X   */
+   /*╚══════════════════════╝*/      @y.j= random(LO, HI)     /*    "    a    "     Y   */
+                                     end   /*j*/              /*X  &  Y  make the point.*/
+          A= 1;  B= 2                            /* [↓]  MIND  is actually the squared  */
+minD= (@x.A - @x.B)**2   +   (@y.A - @y.B)**2    /* distance between the 1st two points.*/
+                                                 /* [↓]  use of XJ & YJ speed things up.*/
+    do   j=1    for N-1;  xj= @x.j;   yj= @y.j   /*find min distance between a point ···*/
+      do k=j+1  for N-j-1                        /*  ··· and all other (higher) points. */
+      sd= (xj - @x.k)**2   +   (yj - @y.k)**2    /*compute squared distance from points.*/
+      if sd<minD  then parse  value     sd  j  k      with      minD  A  B
+      end   /*k*/                                /* [↑]  needn't take SQRT of SD  (yet).*/
+    end     /*j*/                                /* [↑]  when done, A & B are the points*/
+                 $= 'For '   N   " points, the minimum distance between the two points:  "
+say $ center("x", w, '═')" "     center('y', w, "═")     '  is: '     sqrt( abs(minD)) / 1
+say left('', length($) - 1)      "["right(@x.A, w)','           right(@y.A, w)"]"
+say left('', length($) - 1)      "["right(@x.B, w)','           right(@y.B, w)"]"
+exit 0                                           /*stick a fork in it,  we're all done. */
+/*──────────────────────────────────────────────────────────────────────────────────────*/
+sqrt: procedure; parse arg x; if x=0  then return 0; d=digits(); m.=9; numeric form; h=d+6
+      numeric digits;  parse value format(x,2,1,,0) 'E0' with g 'E' _ .;  g= g *.5'e'_ % 2
+        do j=0  while h>9;      m.j= h;              h= h % 2  +  1;  end  /*j*/
+        do k=j+5  to 0  by -1;  numeric digits m.k;  g= (g+x/g)*.5;   end  /*k*/; return g