public static double AreaSwitch(this TagShape s)
{
switch (s.Tag)
{
case ShapeCase.Circle:
return(Math.PI * s.Radius * s.Radius);
case ShapeCase.EquilateralTriangle:
return(Math.Sqrt(3.0) / 4.0 * s.SideLen * s.SideLen);
case ShapeCase.Rectangle:
return(s.Height * s.Width);
default:
throw new InvalidOperationException();
}
}
public static TagShape ToTagShape(this Shape s) =>
s.Match(
circle => TagShape.Circle(circle.Radius),
triangle => TagShape.EquilateralTriangle(triangle.SideLen),
rectangle => TagShape.Rectangle(rectangle.Height, rectangle.Width));
public static double AreaMatch(this TagShape s) =>
s.Match(
radius => Math.PI * radius * radius,
sideLen => Math.Sqrt(3.0) / 4.0 * sideLen * sideLen,
(height, width) => height * width);