Path: utzoo!mnetor!uunet!mcvax!diku!seindal
From: seindal@diku.dk (Rene' Seindal)
Newsgroups: comp.unix.questions
Subject: A (silly) plot(5) question.
Message-ID: <3696@diku.dk>
Date: 2 Mar 88 21:55:50 GMT
Organization: DIKU, U of Copenhagen, DK
Lines: 31


I have been reading the man page for plot(5) a few times recently,
since I was supposed to write a plot to PostScript filter.  The
problem is the specification for "arc" command.  I quote from the
manual: 

	"arc: The first four bytes give the center, the
	next four give the starting point, and the last
	four give the end point of a circular arc.  The
	least significant coordinate of the end point is
	used only to determine the quadrant.  The arc is
	drawn counter-clockwise."

My question: What is the least significant coordinate of a point?  Even
with my best will, this sentence is nonsenses.

Those plot filters that implements this function assumes that the end
point lies on the circle given by the first two points (but doesn't
bother to check it).   Given other points, they will draw various
strange circular arcs.  Points on the tangent at the starting point is
especially amusing. 

I can make the specification make sense if the offending sentence is
removed.  It is then clear that the end-point *must* be on the circle.

If anybody can help clarify this, I am greateful.


Rene' Seindal, DIKU, U. of Copenhagen. (seindal@diku.dk)

			"Parentheses is (not) of much use."