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Groups > comp.lang.forth > #135646

General routine for a polyline or a polygon

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Can be used with any LINE command, as long as it draws a line between 
two absolute coordinates. ( x1 y1 x2 y2 --):

: line cr rot >r -rot r> rot 0 .r ." ," . 0 .r ." ," . ;   \ dummy line word

variable 'lineto                                           \ stores 
address of (lineto)

[: drop drop drop drop ;]         constant (cancel)        ( x1 y1 x2 y2 --)
[: 2dup 2>r line 2r> 'lineto @ ;] constant (lineto)        ( x1 y1 x2 y2 
-- x2 y2 xt)
[: 2dup (lineto) ;]               constant (moveto)        ( x y -- x y 
x y xt)
: polygon[ ['] line (moveto) ;                             ( -- xt1 xt2)
: polyline[ (cancel) (moveto) ;                            ( -- xt1 xt2)
: +point rot execute ;                                     ( x1 y1 xt x2 
y2 -- x2 y2 xt)
: ]poly drop 2>r rot 2r> +point ;                          ( xt1 x1 y1 
x2 y2 xt2 --)

(lineto) 'lineto !

This is a sample application:

polygon[                               \ start a polygon
    75 300 +point                       \ now issue all the points
   161 329 +point
   161 419 +point
   215 347 +point
   301 373 +point
   250 300 +point
   301 227 +point
   215 253 +point
   161 181 +point
   161 271 +point
]poly                                  \ close the polygon

All the points should be listed now (filtered output):

75,300 161,329  ok 6
161,329 161,419  ok 6
161,419 215,347  ok 6
215,347 301,373  ok 6
301,373 250,300  ok 6
250,300 301,227  ok 6
301,227 215,253  ok 6
215,253 161,181  ok 6
161,181 161,271  ok 6
75,300 161,271  ok

Hans Bezemer

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General routine for a polyline or a polygon Hans Bezemer <the.beez.speaks@gmail.com> - 2026-09-10 12:46 +0200
  Re: General routine for a polyline or a polygon dxf <dxforth@gmail.com> - 2026-09-10 23:33 +1000
    Re: General routine for a polyline or a polygon Hans Bezemer <the.beez.speaks@gmail.com> - 2026-09-10 19:22 +0200
      Re: General routine for a polyline or a polygon Hans Bezemer <the.beez.speaks@gmail.com> - 2026-09-11 13:30 +0200
        Re: General routine for a polyline or a polygon dxf <dxforth@gmail.com> - 2026-09-12 01:04 +1000
          Re: General routine for a polyline or a polygon dxf <dxforth@gmail.com> - 2026-09-12 02:34 +1000
            Re: General routine for a polyline or a polygon Hans Bezemer <the.beez.speaks@gmail.com> - 2026-09-11 19:22 +0200

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