[ColorForth] Circle Primitive, happy for response

["Jimmy Söderman" <hiraganagos@xxxxxxxxxxx>]

Nice indeed, and that AT & COLOR would make it blend in perfectly into the 
environement (would work as global variables/functions anyway, right?).
Btw I´ll post my algorithm in pseudocode (its 100% tested and works like a 
charm) as Its the fastest & shortest circle algo ive had thru my years, if 
nothing else would be great fun see it in CF

Cheers.

CIRCLE(r)
a=r
c=-r
b=0
Repeat
symmetric(b,a)
symmetricplot(a,b)
b=b+1:c=c+b
If c=>0 Then a=a-1:c=c-a
Until a<b

symmetricplot(x,y)
Plot ATX+x,ATY+y
Plot ATX+x,ATY-y
Plot ATX-x,ATY+y
Plot ATX-x,ATY-y

> From: Mark Slicker <maslicke@xxxxxxxxxxx>
> Reply-To: ColorForth@xxxxxxxxxxxxxxxxxx
> To: "ColorForth List Member"  <ColorForth@xxxxxxxxxxxxxxxxxx>
> Subject: [ColorForth] Circle Primitive,  happy for response
> Date: Sat, 15 Jun 2002 23:50:54 -0400 (EDT)
>
> Hello,
>
> Here is my take. It was easier to just write this since yours was
> untested, and there were some misunderstandings of the colorForth
> vocabulary. However it uses the ideas of your implementation, and the
> bresenham algorithm from a book of mine.
>
> circle takes (radius x y color), though it might be better though to use
> the colorForth words 'at' and 'color', to define the position and color,
> to fit in with the other drawing functions. Just thought of this now.
>
> Mark
>
> ( Circle ) empt macro
> : 2! [a!] 28966 3, [drop] ; forth variable b variable c variable d
> variable de variable se
> : point2 1024 * over negate + 2* b @ + c @ over 2! swap 4 * + c @ swap
> 2! ;
> : 2over over over ;
> : points 2over point2 2over negate point2 2over swap 2over negate point2
> point2 ;
> : d? d @ 0 less drop if de @ + d ! 2 de +! 2 se +! ; then se @ + d ! 2 de
> +! 4 se +! -1 + ;
> : circle c ! 1024 * + 2* 1e80000 + b ! 0 swap points dup - 2 + d ! dup -2
> * 5 + se ! 3 de !
> : n less if d? points 1 u+ n ; then drop drop ;
> : ok show black screen 100 400 400 ffff circle keyboard ;
> ------------------------
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