From 5a01e6c93947d86e0a7021ae596530a31ba9bb92 Mon Sep 17 00:00:00 2001
From: James Goppert <james.goppert@gmail.com>
Date: Tue, 16 Feb 2016 12:22:08 -0500
Subject: [PATCH] Added slice function for matrix.

---
 README.md           | 16 ++++++++++++++++
 matrix/Matrix.hpp   |  7 +++++++
 test/CMakeLists.txt |  3 ++-
 test/slice.cpp      | 25 +++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 test/slice.cpp

diff --git a/README.md b/README.md
index 3da2001634..cf5c05c62c 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,8 @@ A simple and efficient template based matrix library.
 
 ## Example
 
+See the test directory for detailed examples. Some simple examples are included below:
+
 ```c++
 	// define an euler angle (Body 3(yaw)-2(pitch)-1(roll) rotation)
 	float roll = 0.1f;
@@ -91,4 +93,18 @@ A simple and efficient template based matrix library.
 	// correction
 	x += K*r;
 
+	// slicing
+    float data[9] = {0, 2, 3,
+                     4, 5, 6,
+                     7, 8, 10
+                    };
+    SquareMatrix<float, 3> A(data);
+
+	// Slice a 3,3 matrix starting at row 1, col 0,
+	// with size 2 x 3, warning, no size checking
+    Matrix<float, 2, 3> B(A.slice<2, 3>(1, 0));
+
+	// this results in:
+	// 4, 5, 6
+	// 7, 8, 10
 ```
diff --git a/matrix/Matrix.hpp b/matrix/Matrix.hpp
index dedd2065a7..4991002fd3 100644
--- a/matrix/Matrix.hpp
+++ b/matrix/Matrix.hpp
@@ -317,6 +317,13 @@ public:
         return transpose();
     }
 
+    template<size_t P, size_t Q>
+    Matrix<Type, P, Q> slice(size_t x0, size_t y0) const
+    {
+        Matrix<Type, P, Q> res(&(_data[x0][y0]));
+        return res;
+    }
+
     void setZero()
     {
         memset(_data, 0, sizeof(_data));
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 28c55533de..2cff34c3ac 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,6 +1,7 @@
 set(tests
 	setIdentity
 	inverse
+	slice
 	matrixMult
 	vectorAssignment
 	matrixAssignment
@@ -33,4 +34,4 @@ if (${CMAKE_BUILD_TYPE} STREQUAL "Profile")
 		WORKING_DIRECTORY ${CMAKE_BUILD_DIR}
 		DEPENDS test_build
 		)
-endif()
\ No newline at end of file
+endif()
diff --git a/test/slice.cpp b/test/slice.cpp
new file mode 100644
index 0000000000..1f0bf99819
--- /dev/null
+++ b/test/slice.cpp
@@ -0,0 +1,25 @@
+#include <stdio.h>
+
+#include <matrix/math.hpp>
+#include "test_macros.hpp"
+
+using namespace matrix;
+
+int main()
+{
+    float data[9] = {0, 2, 3,
+                     4, 5, 6,
+                     7, 8, 10
+                    };
+    float data_check[6] = {
+        4, 5, 6,
+        7, 8, 10
+    };
+    SquareMatrix<float, 3> A(data);
+    Matrix<float, 2, 3> B_check(data_check);
+    Matrix<float, 2, 3> B(A.slice<2, 3>(1, 0));
+    TEST(isEqual(B, B_check));
+    return 0;
+}
+
+/* vim: set et fenc=utf-8 ff=unix sts=0 sw=4 ts=4 : */