/// <inheritdoc/>
public override bool ValidateOldTheorem(ContextualPicture contextualPicture, Theorem oldTheorem)
{
// If we don't care whether the intersection point is outside or inside of the picture,
// then there is no reason to say a theorem is invalid
if (!ExpectAnyExternalIntersection)
{
return(true);
}
// Otherwise it might have happened that the new point is the one where the old theorem
// stated an intersection theorem. We need to check this. Let's take the new point
var newPoint = contextualPicture.NewPoints.FirstOrDefault();
// If the last object hasn't been a point, then nothing as explained could have happened
if (newPoint == null)
{
return(true);
}
// Otherwise we need to check whether the old theorem doesn't state that some objects
// have an intersection point equal to the new point
return(oldTheorem.InvolvedObjects
// We know the objects are with points
.Cast <TheoremObjectWithPoints>()
// For each we will find the corresponding geometric object definable by points
.Select(objectWithPoints =>
{
// If the object is defined explicitly, then we simply ask the picture to do the job
if (objectWithPoints.DefinedByExplicitObject)
{
return (DefinableByPoints)contextualPicture.GetGeometricObject(objectWithPoints.ConfigurationObject);
}
// Otherwise we need to find the inner points
var innerPoints = objectWithPoints.Points
// As geometric objects
.Select(contextualPicture.GetGeometricObject)
// They are points
.Cast <PointObject>()
// Enumerate
.ToArray();
// Base on the type of object we will take all lines / circles passing through the first point
return (objectWithPoints switch
{
// If we have a line, take lines
LineTheoremObject _ => innerPoints[0].Lines.Cast <DefinableByPoints>(),
// If we have a circle, take circles
CircleTheoremObject _ => innerPoints[0].Circles,
// Unhandled cases
_ => throw new TheoremFinderException($"Unhandled type of {nameof(TheoremObjectWithPoints)}: {objectWithPoints.GetType()}")
})
// Take the first line or circle that contains all the points
.First(lineOrCircle => lineOrCircle.ContainsAll(innerPoints));
})
/// <summary>
/// Finds all options for changing the definition of a given old theorem object based on the new (last)
/// configuration object, which might have geometric properties related to this old object (for example,
/// if the new object is a point and the old one is a line/circle, then it might lie on it). This includes
/// even an option of not changing the definition at all, i.e. returning the original old object.
/// </summary>
/// <param name="oldTheoremObject">The old theorem object for which we're looking for definition change options.</param>
/// <param name="contextualPicture">The contextual picture that represents the configuration.</param>
/// <returns>The enumeration of all possible definition changes, including no change.</returns>
private static IEnumerable <TheoremObject> FindDefinitionChangeOptions(TheoremObject oldTheoremObject, ContextualPicture contextualPicture)
{
// Find the new object of the configuration
var newConfigurationObject = contextualPicture.Pictures.Configuration.LastConstructedObject;
// Find its geometric version
var newGeometricObject = contextualPicture.GetGeometricObject(newConfigurationObject);
// Switch based on the type of old object
switch (oldTheoremObject)
{
// If we have a point or line segment (internally consisting of points...)
case PointTheoremObject _:
case LineSegmentTheoremObject _:
// Then there is no way to find a new definition of the object,
// i.e. we return the 'no change of definition' option
return(new[] { oldTheoremObject });
// If we have an object with points...
case TheoremObjectWithPoints objectWithPoints:
#region Find its geometric version
// We're going to find the corresponding geometric version
DefinableByPoints geometricObjectWithPoints = default;
// If our object is defined explicitly
if (objectWithPoints.DefinedByExplicitObject)
{
// Use the internal configuration object to get the definition directly
geometricObjectWithPoints = (DefinableByPoints)contextualPicture.GetGeometricObject(objectWithPoints.ConfigurationObject);
}
// Otherwise it's defined by points
else
{
// Get the points corresponding to its points
var geometricPoints = objectWithPoints.Points
// For each find the geometric point
.Select(contextualPicture.GetGeometricObject)
// We know they're points
.Cast <PointObject>()
// Enumerate
.ToArray();
// Find the right object based on the type of the theorem object with points
geometricObjectWithPoints = (objectWithPoints switch
{
// Looking for the line that contains our points
// It certainly passes through the first point
LineTheoremObject _ => geometricPoints[0].Lines.First(line => line.ContainsAll(geometricPoints)) as DefinableByPoints,
// Looking for the circle that contains our points
// It certainly passes through the first point
CircleTheoremObject _ => geometricPoints[0].Circles.First(circle => circle.ContainsAll(geometricPoints)),
// Unhandled cases
_ => throw new TheoremFinderException($"Unhandled type of {nameof(TheoremObjectWithPoints)}: {objectWithPoints.GetType()}")
});
}
