[metapost] tangent

[Honza Prachar]

On Mon, 17 Jan 2005, Laurence Finston wrote:

> You'll have to be more specific.  For example, a `path' can represent
> a straight line segment, in which case the problem reduces to
> determining whether `z' lies on that line.  It could also represent an
> `ellipse', so if `z' is located at one of the corners of the
> surrounding rectangle, it lies on two tangents to the `path'.

I meant general curve. I found solution using loop to determine right
point, where tangent and curve have same direction. But I do not believe
it is the simpliest solution.

`Honza` Prachar