From 2feea51b078cc53663e411bf80e35044c1ef4a07 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 9 Nov 2017 12:45:59 +0200
Subject: [PATCH] Add row and column accessors to Matrix

---
 source/linal/matrix.h |  3 +++
 source/linal/vector.h | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/source/linal/matrix.h b/source/linal/matrix.h
index 1c831be..daf9cb8 100644
--- a/source/linal/matrix.h
+++ b/source/linal/matrix.h
@@ -36,6 +36,9 @@ public:
 	T &operator()(unsigned i, unsigned j) { return element(i, j); }
 	const T &operator()(unsigned i, unsigned j) const { return element(i, j); }
 
+	Vector<T, M> column(unsigned i) const { return Vector<T, M>(data+M*i); }
+	Vector<T, N> row(unsigned i) const { return Vector<T, N>(data+i, M); }
+
 	template<unsigned P, unsigned Q>
 	Matrix<T, P, Q> select(const Vector<unsigned, P> &, const Vector<unsigned, Q> &) const;
 
diff --git a/source/linal/vector.h b/source/linal/vector.h
index 152c26e..9a9d028 100644
--- a/source/linal/vector.h
+++ b/source/linal/vector.h
@@ -78,6 +78,11 @@ public:
 
 	Vector();
 	Vector(const T *);
+
+	/** Constructs a vector from an array of interleaved values.  Intended for
+	use by Matrix row accessor. */
+	Vector(const T *, unsigned);
+
 	Vector(T, T);
 	Vector(T, T, T);
 	Vector(T, T, T, T);
@@ -113,6 +118,13 @@ inline Vector<T, N>::Vector(const T *d)
 		(*this)[i] = d[i];
 }
 
+template<typename T, unsigned N>
+inline Vector<T, N>::Vector(const T *d, unsigned stride)
+{
+	for(unsigned i=0; i<N; ++i)
+		(*this)[i] = d[i*stride];
+}
+
 /* The compiler won't instantiate these unless they are used.  Trying to use
 them on the wrong class results in an error. */
 template<typename T, unsigned N>
-- 
2.43.0