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Re: Circles

From: Jean Abou Samra
Subject: Re: Circles
Date: Thu, 11 Aug 2022 08:03:32 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0

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
} 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:

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


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