43 lines
4.0 KiB
Rexx
43 lines
4.0 KiB
Rexx
/*REXX program plots three circles using midpoint/Bresenham's circle algorithm. */
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@.= '·' /*fill the array with middle─dots char.*/
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minX=0; maxX=0; minY=0; maxY=0 /*initialize the minimums and maximums.*/
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call drawCircle 0, 0, 8, '#' /*plot 1st circle with pound character.*/
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call drawCircle 0, 0, 11, '$' /* " 2nd " " dollar " */
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call drawCircle 0, 0, 19, '@' /* " 3rd " " commercial at. */
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border=2 /*BORDER: shows N extra grid points.*/
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minX=minX-border*2; maxX=maxX+border*2 /*adjust min and max X to show border*/
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minY=minY-border ; maxY=maxY+border /* " " " " Y " " " */
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if @.0.0==@. then @.0.0='┼' /*maybe define the plot's axis origin. */
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/*define the plot's horizontal grid──┐ */
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do h=minX to maxX; if @.h.0==@. then @.h.0='─'; end /* ◄───────────┘ */
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do v=minY to maxY; if @.0.v==@. then @.0.v='│'; end /* ◄──────────┐ */
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/*define the plot's vertical grid───┘ */
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do y=maxY by -1 to minY; _= /* [↓] draw grid from top ──► bottom.*/
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do x=minX to maxX; _=_ || @.x.y /* ◄─── " " " left ──► right. */
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end /*x*/ /* [↑] a grid row should be finished. */
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say _ /*display a single row of the grid. */
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end /*y*/
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exit /*stick a fork in it, we're all done. */
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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drawCircle: procedure expose @. minX maxX minY maxY
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parse arg xx,yy,r 1 y,plotChar; fx=1; fy=-2*r /*get X,Y coördinates*/
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f=1-r
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do x=0 while x<y /*▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒*/
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if f>=0 then do; y=y-1; fy=fy+2; f=f+fy; end /*▒*/
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fx=fx+2; f=f+fx /*▒*/
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call plotPoint xx+x, yy+y /*▒*/
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call plotPoint xx+y, yy+x /*▒*/
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call plotPoint xx+y, yy-x /*▒*/
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call plotPoint xx+x, yy-y /*▒*/
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call plotPoint xx-y, yy+x /*▒*/
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call plotPoint xx-x, yy+y /*▒*/
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call plotPoint xx-x, yy-y /*▒*/
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call plotPoint xx-y, yy-x /*▒*/
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end /*x*/ /* [↑] place plot points ══► plot.▒▒▒▒▒▒▒▒▒▒▒▒▒*/
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return
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/*──────────────────────────────────────────────────────────────────────────────────────*/
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plotPoint: parse arg c,r; @.c.r=plotChar /*assign a character to be plotted. */
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minX=min(minX,c); maxX=max(maxX,c) /*determine the minimum and maximum X.*/
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minY=min(minY,r); maxY=max(maxY,r) /* " " " " " Y.*/
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return
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