Internal classes for constructing circles tangent to circles and lines.

[EarlinLutz]

Class ImplicitCurve2d is an abstract class for curves which have a function f(x,y) which is zero for all points on the curve (and nonzero elsewhere). Although most common curves (circles, lines, hyperbola, ellipse) can satisfy this implicit f(x,y)=0 condition AND have a parametric form (x,y,) = g(t) for a parameter t, the parametric form is NOT universal, and the "implicit curve" category warrants distinct implementations for some constructions.

The following concrete implementations are included in this category:

• UnboundedCircle2d -- circle defined by center and radius
• UnboundedLine2d -- line defined by any point on the line and a normal vector.
• UnboundedHyperbola2d - a hyperbola with implicit form u^2-v^2=1 in a (possibly skewed) local coordinate system
• UnboundedEllipse2d - an ellipse with implicit form u^2+v^2=1 in a (possibly skewed) local coordinate system
• ConstructionConstraint -- a curve reference and constraint type such as tangentTo, perpendicularTo, or fixedRadius
• ConstraintSet -- an array of ConstructionConstraints, with methods to examine the constraints (e.g. 2 for a line or 3 for a circle) and dispatch to specific computation to produce geometry satisfying the constraints.

The class ConstrainedConstruction contains static methods for common circle constructions. Each of these is a specific method to encapsulate the construction. They may be called directly if caller has identified the combination. If caller has varied construction constraints, they may be passed as an array to the to dispatch logic noted further below.

• circles
  • tangent to 3 lines
  • tangent to 2 lines and one circle
  • tangent to a line and 2 circles
  • tangent to 3 circles
  • tangent to 2 circles and with given radius
  • tangent to 2 lines and with given radius
  • tangent to a line and a circle and with given radius
• lines:
  • tangent to 2 circles
  • perpendicular to a line and a circle
  • perpendicular to 2 circles
  • perpendicular to a line and tangent to a circle.
  • perpendicular to a circle and tangent to a circle

The following methods on ConstructionSet have logic to examine 2 or 3 constraints and dispatch to an appropriate method in the lists above:

• constructConstrainedCircles -- array of 3 constraints dispatched to appropriate circle logic
• constructConstrainedLines -- array of 2 constraints dispatched to appropriate line logic

(In the tangency constructions, the input circles may be zero radius, i.e. act as isolated points.)

[dassaf4]

Just a reminder to update NextVersion.md with a nice example of the API: code and image output. You can even scrape this from the tests. This will help users see what the API does, and how to use it.