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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