Geometer

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New Features
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- Added Tensor.dtype property
- Added parameters to Tensor class to control ndarray creation (e.g. for setting the dtype)
- Quadrics can now be normalized using their (pseudo-) determinant to reduce numerical errors
- The underlying arrays of tensors are copied less often (controlled by copy parameter)
- Implemented addition/subtraction of points to a quadric
- Transformations can be applied to any object of type Tensor
- More robust algorithm for calculating the intersection of conics
- Added a determinant function that is faster for matrices in dimension 2 and 3
- Updated dependencies (up to NumPy 1.19 and SymPy 1.6 now supported)

Bug fixes
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- Fixed error that was raised when integer arrays are normalized in the join/meet function
- Fixed issues caused by an array not being converted to a Point object in Line.base_point and Line.directions
- Correct handling of special cases in the calculation of the crossing number in Polygon.contains
- Trying to raise an arbitrary tensor to power zero now correctly raises an NotImplementedError
- Equality of polytopes is determined correctly even if the vertices are in a different order

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New Features
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- New adjugate function in utils.math
- New algorithms for Segment.contains, Conic.intersect & Conic.from_crossratio

Bug fixes
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- Fixed an issue with numerical stability when intersecting transformed polytopes (issue 24)
- Conic.components uses a better algorithm that should give correct results in all cases
- Quadric.intersect no longer throws a ValueError when a 3D line has only a single point of intersection
- Line.base_point will now try to always return finite points and Line.direction a point at infinity
- Arrays with small component values are handled correctly by the is_multiple function
- Fixed an issue with Polygon.contains that caused the direction used in the method to be close to zero (issue 25)
- Transformation of line in 3D now works correctly
- The functions null_space and orth now use the same threshold values as Matlab for truncating the singular values

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New Features
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- Added properties shape, rank and T to Tensor class
- Tensor instances can be raised to an arbitrary positive power
- Dynamic calculation of center and radius attributes of RegularPolygon instances
- Added RegularPolygon.inradius property
- Polytope is now a subclass of Tensor
- Added functions for generating transforms that perform scaling and reflections
- Added Polygon.centroid property
- Updated numpy to version 1.18

Bug fixes
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- Transformations are now applied correctly to quadrics and conics
- Fixed bug that made transformation of Cuboid & RegularPolygon fail (issue 23)
- Raising transformations to a power (other than 1) is calculated correctly
- Tolerance parameters are correctly used in Tensor.__eq__
- Scalar multiplication with Points is calculated correctly using normalized_array
- Fixed copy method Tensor subclasses
- Return real angles instead of angles with complex type
- Fixed init method of regular polygons that aren't centered at the origin
- Indices passed to Tensor constructor are validated and negative indices converted
- Fixed init method of Cone & Cylinder classes

Deprecations
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- Deprecated AlgebraicCurve, Subspace.polygons, Plane.polygon, Quadric.polygon and the
module utils.polynomial in preparation of removal of sympy as dependency

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New Features
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- New shapes module that implements line segments, polygons and general polytopes
- New Sphere class (a subclass of Quadric) that works in any dimension
- New classes representing a cone and a cylinder in 3D
- Tensor has a new tensor_product method to calculate the tensor product with another tensor
- Ellipse class that constructs a conic from center and radius
- Added Conic.foci and Conic.polar
- Construct a conic from its focal points, using a tangent line or a cross ratio
- Faster and more general intersect method for quadrics
- Refactored & documented the code for calculation of tensor diagrams
- New KroneckerDelta tensor
- TensorDiagram calculates results differently, using free indices from front to back
- New method TensorDiagram.add_node to add tensors without edge to the diagram
- Added Circle.intersection_angle to calculate the angle of intersection of two circles
- is_perpendicular now works with two planes
- New function is_multiple in utils module

Bug fixes
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- Plane.perpendicular now also works for points that lie on the plane
- Addition/Subtraction of subspaces and points works in more cases
- Adding a point at infinity to another point will give a finite point moved in that direction
- Globally accessible tolerance parameters to avoid inaccurate calculations (issue 22)
- Fixed Transformation.from_points

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New Features
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- Optimized performance of Conic, LeviCivitaTensor and TensorDiagram
- More operations are now compatible with higher-dimensional objects
- New Subspace class that can be used to represent subspaces of any dimension
- New repr and copy methods of Tensor
- scipy is no longer a dependency

Bug fixes
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- Rotation in 3D now returns the correct transformation if the axis is not a normalized vector
- Line.perpendicular now also works for points tha lie on the line

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