Re: Circles

[Jean Abou Samra]

Le 11/08/2022 à 06:14, Andrew Bernard a écrit :
> Ah yes it is in the postscript area of the source code.
>
> /draw_circle % filled? radius thickness draw_circle
> {
>         setlinewidth    % f? r
>         currentpoint    % f? r x0 y0
>         3 2 roll        % f? x0 y0 r
>         dup 0 rmoveto
>         0 360 arc closepath
>         stroke_and_fill?
> } bind def
>
> Simple use of 360 degree arc. Answers what I wanted to know.


OK. Out of curiosity, what was the context?

> There's a lot of oldish webpages with complex Bezier curve 
> constructions for circles.

Those must be approximate constructions. It is not mathematically 
possible to construct a Bézier curve which is at the same time an exact 
circle.


> Perhaps a version earlier than Postscript 3 did not have the arc 
> operator. Otherwise I don't know why you would bother.

I see arc in the PostScript level 2 manual:

https://www.os2site.com/sw/dev/openwatcom/docs/postscript_level_2_reference_manual.pdf

and given it's such a fundamental command, I am pretty sure it has been 
there from the beginning.

Best,
Jean