From ffb043ce670d733decc03c6e4240a4e6d980caec Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 13 Nov 2014 23:18:47 +0200
Subject: [PATCH] Clearer API for slicing and dicing vectors, and also matrices

---
 source/linal/matrix.h | 14 +++++++++++++
 source/linal/vector.h | 47 ++++++++++++++++++++++++++++++++-----------
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/source/linal/matrix.h b/source/linal/matrix.h
index f18eb2f..929c482 100644
--- a/source/linal/matrix.h
+++ b/source/linal/matrix.h
@@ -30,6 +30,9 @@ public:
 	T &operator()(unsigned i, unsigned j) { return element(i, j); }
 	const T &operator()(unsigned i, unsigned j) const { return element(i, j); }
 
+	template<unsigned P, unsigned Q>
+	Matrix<T, P, Q> block(unsigned, unsigned) const;
+
 	Matrix &operator*=(T);
 	Matrix &operator/=(T);
 	Matrix &operator+=(const Matrix &);
@@ -81,6 +84,17 @@ inline Matrix<T, M, N> Matrix<T, M, N>::from_rows(const Vector<T, N> *v)
 	return m;
 }
 
+template<typename T, unsigned M, unsigned N>
+template<unsigned P, unsigned Q>
+inline Matrix<T, P, Q> Matrix<T, M, N>::block(unsigned y, unsigned x) const
+{
+	Matrix<T, P, Q> r;
+	for(unsigned j=0; j<P; ++j)
+		for(unsigned i=0; i<Q; ++i)
+			r(j, i) = element(y+j, x+i);
+	return r;
+}
+
 template<typename T, unsigned M, unsigned N>
 inline Matrix<T, M, N> &Matrix<T, M, N>::operator*=(T s)
 {
diff --git a/source/linal/vector.h b/source/linal/vector.h
index 9ef46fd..6dfe6ca 100644
--- a/source/linal/vector.h
+++ b/source/linal/vector.h
@@ -81,10 +81,9 @@ public:
 	Vector(T, T, T, T);
 	template<typename U>
 	Vector(const Vector<U, N> &);
-	template<typename U>
-	Vector(const Vector<U, N-1> &, U);
-	template<typename U>
-	explicit Vector(const Vector<U, N+1> &);
+
+	template<unsigned M>
+	Vector<T, M> slice(unsigned) const;
 
 	Vector &operator*=(T);
 	Vector &operator/=(T);
@@ -145,20 +144,44 @@ inline Vector<T, N>::Vector(const Vector<U, N> &v)
 }
 
 template<typename T, unsigned N>
-template<typename U>
-inline Vector<T, N>::Vector(const Vector<U, N-1> &v, U s)
+inline Vector<T, N+1> compose(const Vector<T, N> &v, T s)
 {
-	for(unsigned i=0; i<N-1; ++i)
-		(*this)[i] = v[i];
-	(*this)[N-1] = s;
+	Vector<T, N+1> r;
+	for(unsigned i=0; i<N; ++i)
+		r[i] = v[i];
+	r[N] = s;
+	return r;
 }
 
 template<typename T, unsigned N>
-template<typename U>
-inline Vector<T, N>::Vector(const Vector<U, N+1> &v)
+inline Vector<T, N+1> compose(T s, const Vector<T, N> &v)
 {
+	Vector<T, N+1> r;
 	for(unsigned i=0; i<N; ++i)
-		(*this)[i] = v[i];
+		r[i] = v[i];
+	r[N] = s;
+	return r;
+}
+
+template<typename T, unsigned N, unsigned M>
+inline Vector<T, N+M> compose(const Vector<T, N> &v1, const Vector<T, M> &v2)
+{
+	Vector<T, N+M> r;
+	for(unsigned i=0; i<N; ++i)
+		r[i] = v1[i];
+	for(unsigned i=0; i<M; ++i)
+		r[N+i] = v2[i];
+	return r;
+}
+
+template<typename T, unsigned N>
+template<unsigned M>
+inline Vector<T, M> Vector<T, N>::slice(unsigned j) const
+{
+	Vector<T, M> r;
+	for(unsigned i=0; i<M; ++i)
+		r[i] = (*this)[j+i];
+	return r;
 }
 
 template<typename T, unsigned N>
-- 
2.43.0