Data commit

Task/Julia-set/REXX/julia-set.rexx

@@ -0,0 +1,21 @@
+/*REXX program  displays  an  ASCII plot   (character plot)   of a  Julia set.          */
+parse arg real imag fine .                       /*obtain optional arguments from the CL*/
+if real=='' | real==","  then real= -0.8         /*Not specified?  Then use the default.*/
+if imag=='' | imag==","  then imag=  0.156       /* "      "         "   "   "     "    */
+if fine=='' | fine==","  then fine= 50           /* "      "         "   "   "     "    */
+_=scrsize(); parse var _ sd sw; sd=sd-4; sw=sw-1 /*obtain useable area for the terminal.*/
+                                                 /*$:  the plot line that is constructed*/
+         do   v= -sd%2  to sd%2;     $=          /*step through  vertical   axis values.*/
+           do h= -sw%2  to sw%2                  /*  "     "    horizontal    "     "   */
+           x=h/sw*2                              /*calculate the initial   X   value.   */
+           y=v/sd*2                              /*    "      "     "      Y     "      */
+           @='■';    do fine                     /*FINE: is the "fineness" for the plot.*/
+                     zr=x*x - y*y + real         /*calculate a new   real   Julia point.*/
+                     zi=x*y*2     + imag         /*    "     "  "  imaginal   "     "   */
+                     if zr**2>10000  then do; @=' '; leave; end    /*is  ZR  too large? */
+                     x=zr;    y=zi                                 /*use this new point.*/
+                     end   /*50*/
+           $=$ || @                              /*append the plot char to the plot line*/
+           end            /*h*/
+         if $\=''  then say strip($, 'T')        /*only display a plot line if non-blank*/
+         end   /*v*/                             /*stick a fork in it,  we're all done. */