Add Axis2d.intersectionPoint, Axis2d.fromLineSegment, and QuadraticSpline2d.nearestPoint

[MartinSStewart]

I've added Axis2d.intersectionPoint, Axis2d.fromLineSegment, and QuadraticSpline2d.nearestPoint. I've only written tests for Axis2d.intersectionPoint. I don't think Axis2d.fromLineSegment needs any. QuadraticSpline2d.nearestPoint definately does but I ran out of energy before I got that far 😅.

[LegenDAirie]

The Axis2d.intersectionPoint is something I would like to use for my project. How might I be able to help this PR along?

[MartinSStewart]

If you'd like to help this PR along then QuadraticSpline2d.nearestPoint still needs some tests to make sure it works correctly. If you just want Axis2d.intersectionPoint then I recommend just copy pasting that code into your project for now.

[ianmackenzie]

OK I think everything in this MR has been merged in, one way or another:

• I added Axis2d.fromLineSegment as LineSegment2d.axis (seemed consistent with LineSegment2d.direction)
• I added Axis2d.intersectionPoint although with a different implementation (when I tried adding some fuzz testing for the implementation in this MR it seemed to have some numerical stability issues, possibly for nearly-vertical axes?)
• I've moved QuadraticSpline2d.nearestPoint into the quadraticspline2d-nearestpoint branch of https://github.com/ianmackenzie/elm-geometry-extra, although when I added a simple test for it I got a bunch of failures so those will need investigating

So I think this MR can now be closed - @MartinSStewart sound good?

[ianmackenzie]

...I'm an idiot, the test I added was dumb and didn't consider the case that the nearest point on the spline might be an endpoint! I'll try a better version and see what happens.

[MartinSStewart]

Sound good! Though I guess this PR will stay open until new tests are made for QuadraticSpline2d.nearestPoint?

[ianmackenzie]

OK just fixed the test for QuadraticSpline2d.nearestPoint and everything seems good now, so I think we can close this MR :slightly_smiling_face: