From 60caa19c84877c89d750140a90e5d891bce30ee7 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 13 Mar 2022 22:08:58 +0200
Subject: [PATCH] Remove SquareMatrix and instead use static_assert to check
 squareness

---
 source/geometry/affinetransformation.h | 10 ++--
 source/linal/dummy.cpp                 |  1 -
 source/linal/matrix.h                  | 39 +++++++++++++++
 source/linal/squarematrix.h            | 66 --------------------------
 4 files changed, 44 insertions(+), 72 deletions(-)
 delete mode 100644 source/linal/squarematrix.h

diff --git a/source/geometry/affinetransformation.h b/source/geometry/affinetransformation.h
index f01ac3a..e311b88 100644
--- a/source/geometry/affinetransformation.h
+++ b/source/geometry/affinetransformation.h
@@ -1,7 +1,7 @@
 #ifndef MSP_GEOMETRY_AFFINETRANSFORMATION_H_
 #define MSP_GEOMETRY_AFFINETRANSFORMATION_H_
 
-#include <msp/linal/squarematrix.h>
+#include <msp/linal/matrix.h>
 #include "angle.h"
 #include "boundingbox.h"
 #include "ray.h"
@@ -55,7 +55,7 @@ class AffineTransformation: public AffineTransformationOps<T, D>
 	friend class AffineTransformationOps<T, D>;
 
 private:
-	LinAl::SquareMatrix<T, D+1> matrix;
+	LinAl::Matrix<T, D+1, D+1> matrix;
 
 public:
 	AffineTransformation();
@@ -67,8 +67,8 @@ public:
 	AffineTransformation &operator*=(const AffineTransformation &);
 	AffineTransformation &invert();
 
-	const LinAl::SquareMatrix<T, D+1> &get_matrix() const { return matrix; }
-	operator const LinAl::SquareMatrix<T, D+1> &() const { return matrix; }
+	const LinAl::Matrix<T, D+1, D+1> &get_matrix() const { return matrix; }
+	operator const LinAl::Matrix<T, D+1, D+1> &() const { return matrix; }
 
 	LinAl::Vector<T, D> transform(const LinAl::Vector<T, D> &) const;
 	LinAl::Vector<T, D> transform_linear(const LinAl::Vector<T, D> &) const;
@@ -79,7 +79,7 @@ public:
 template<typename T, unsigned D>
 inline AffineTransformation<T, D>::AffineTransformation()
 {
-	this->matrix = LinAl::SquareMatrix<T, D+1>::identity();
+	this->matrix = LinAl::Matrix<T, D+1, D+1>::identity();
 }
 
 
diff --git a/source/linal/dummy.cpp b/source/linal/dummy.cpp
index 84d7395..74a8e44 100644
--- a/source/linal/dummy.cpp
+++ b/source/linal/dummy.cpp
@@ -1,6 +1,5 @@
 #include "vector.h"
 #include "matrix.h"
-#include "squarematrix.h"
 #include "dynamicvector.h"
 #include "dynamicmatrix.h"
 
diff --git a/source/linal/matrix.h b/source/linal/matrix.h
index bf21184..2ad0344 100644
--- a/source/linal/matrix.h
+++ b/source/linal/matrix.h
@@ -3,6 +3,7 @@
 
 #include <algorithm>
 #include <ostream>
+#include "matrixops.h"
 #include "vector.h"
 
 namespace Msp {
@@ -26,6 +27,7 @@ public:
 	template<typename U>
 	Matrix(const Matrix<U, M, N> &);
 
+	static Matrix identity();
 	static Matrix from_columns(const Vector<T, M> *);
 	static Matrix from_rows(const Vector<T, N> *);
 
@@ -47,10 +49,13 @@ public:
 	Matrix<T, P, Q> block(unsigned, unsigned) const;
 
 	Matrix &operator*=(T);
+	Matrix &operator*=(const Matrix &);
 	Matrix &operator/=(T);
 	Matrix &operator+=(const Matrix &);
 	Matrix &operator-=(const Matrix &);
 
+	Matrix &invert();
+
 	Matrix &exchange_columns(unsigned, unsigned);
 	Matrix &multiply_column(unsigned, T);
 	Matrix &add_column(unsigned, unsigned, T);
@@ -77,6 +82,16 @@ inline Matrix<T, M, N>::Matrix(const Matrix<U, M, N> &other)
 			element(i, j) = other(i, j);
 }
 
+template<typename T, unsigned M, unsigned N>
+inline Matrix<T, M, N> Matrix<T, M, N>::identity()
+{
+	static_assert(M==N, "An identity matrix must be square");
+	Matrix<T, M, N> m;
+	for(unsigned i=0; i<M; ++i)
+		m(i, i) = T(1);
+	return m;
+}
+
 template<typename T, unsigned M, unsigned N>
 inline Matrix<T, M, N> Matrix<T, M, N>::from_columns(const Vector<T, M> *v)
 {
@@ -127,6 +142,13 @@ inline Matrix<T, M, N> &Matrix<T, M, N>::operator*=(T s)
 	return *this;
 }
 
+template<typename T, unsigned M, unsigned N>
+inline Matrix<T, M, N> &Matrix<T, M, N>::operator*=(const Matrix<T, M, N> &m)
+{
+	static_assert(M==N, "Multiplication-assignment is only possible on square matrices");
+	return *this = *this*m;
+}
+
 template<typename T, unsigned M, unsigned N>
 inline Matrix<T, M, N> operator*(const Matrix<T, M, N> &m, T s)
 {
@@ -216,6 +238,23 @@ inline Matrix<T, M, N> operator-(const Matrix<T, M, N> &m1, const Matrix<T, M, N
 	return r -= m2;
 }
 
+template<typename T, unsigned M, unsigned N>
+inline Matrix<T, M, N>& Matrix<T, M, N>::invert()
+{
+	static_assert(M==N, "Inversion is only possible on square matrices");
+	Matrix<T, M, N> r = identity();
+	gauss_jordan(*this, r);
+	return *this = r;
+}
+
+template<typename T, unsigned S>
+inline Matrix<T, S, S> invert(const Matrix<T, S, S> &m)
+{
+	Matrix<T, S, S> temp = m;
+	Matrix<T, S, S> r = Matrix<T, S, S>::identity();
+	return gauss_jordan(temp, r);
+}
+
 template<typename T, unsigned M, unsigned N>
 inline bool operator==(const Matrix<T, M, N> &a, const Matrix<T, M, N> &b)
 {
diff --git a/source/linal/squarematrix.h b/source/linal/squarematrix.h
deleted file mode 100644
index 5b9415a..0000000
--- a/source/linal/squarematrix.h
+++ /dev/null
@@ -1,66 +0,0 @@
-#ifndef MSP_LINAL_SQUAREMATRIX_H_
-#define MSP_LINAL_SQUAREMATRIX_H_
-
-#include <cmath>
-#include "matrix.h"
-#include "matrixops.h"
-
-namespace Msp {
-namespace LinAl {
-
-/**
-A mathematical matrix with S rows and columns.  Some operations are provided
-here that are only possible for square matrices.
-*/
-template<typename T, unsigned S>
-class SquareMatrix: public Matrix<T, S, S>
-{
-public:
-	SquareMatrix() { }
-	SquareMatrix(const T *d): Matrix<T, S, S>(d) { }
-	template<typename U>
-	SquareMatrix(const Matrix<U, S, S> &m): Matrix<T, S, S>(m) { }
-
-	static SquareMatrix identity();
-
-	SquareMatrix &operator*=(const SquareMatrix &);
-	using Matrix<T, S, S>::operator*=;
-
-	SquareMatrix &invert();
-};
-
-template<typename T, unsigned S>
-inline SquareMatrix<T, S> SquareMatrix<T, S>::identity()
-{
-	SquareMatrix<T, S> m;
-	for(unsigned i=0; i<S; ++i)
-		m(i, i) = T(1);
-	return m;
-}
-
-template<typename T, unsigned S>
-SquareMatrix<T, S> &SquareMatrix<T, S>::operator*=(const SquareMatrix<T, S> &m)
-{
-	return *this = *this*m;
-}
-
-template<typename T, unsigned S>
-SquareMatrix<T, S> &SquareMatrix<T, S>::invert()
-{
-	SquareMatrix<T, S> r = identity();
-	gauss_jordan(*this, r);
-	return *this = r;
-}
-
-template<typename T, unsigned S>
-inline SquareMatrix<T, S> invert(const SquareMatrix<T, S> &m)
-{
-	SquareMatrix<T, S> temp = m;
-	SquareMatrix<T, S> r = SquareMatrix<T, S>::identity();
-	return gauss_jordan(temp, r);
-}
-
-} // namespace LinAl
-} // namespace Msp
-
-#endif
-- 
2.43.0