[cairo] Spirolaterals

[Lawrence D'Oliveiro]

I’ve been enhancing my curve script
<https://lists.cairographics.org/archives/cairo/2016-May/027422.html>
to draw spirolaterals
<http://www.mi.sanu.ac.rs/vismath/krawczyk/spdesc00.htm>. Has anyone
else looked at these?

All the examples I have tried work fine--except for those with
reversing turns. My conclusion is that many of the examples shown here
<http://www.mi.sanu.ac.rs/vismath/krawczyk/spdesc03.htm> are mixed up
or just plain mislabelled. For example, in figure 6, the one labelled
(substituting slashes for subscripts) “9/90/1,2,3,4” should actually be
“9/90/1,2,3,9”, “9/90/2,3,4” should be “9/90/1,2,9” and “9/90/2,3,4,5”
should actually be “9/90/1,2,3,4”.

If there were a bug in my code, then for example I wouldn’t get
“9/90/1,2,3” correct--the errors would be more systematic.