added small eigen example

CMakeLists.txt

@@ -2,6 +2,14 @@ cmake_minimum_required(VERSION 3.10)
 
 project(Geometry)
 
+set(CMAKE_CXX_STANDARD 17)
+
 include_directories(${PROJECT_SOURCE_DIR}/include)
 
+add_subdirectory(lib/eigen)
+
 add_executable(Geometry main.cpp)
+
+target_link_libraries(Geometry PUBLIC Eigen3::Eigen)
+
+target_include_directories(Geometry PUBLIC "${PROJECT_BINARY_DIR}" "${PROJECT_SOURCE_DIR}/lib/eigen/Eigen")

include/main.h

@@ -6,9 +6,12 @@
 #define GEOMETRY_MAIN_H
 
 #include <iostream>
+#include <Dense>
 
 using namespace std;
 
+void eigenExample();
+
 int main();
 
 #endif //GEOMETRY_MAIN_H

main.cpp

@@ -1,6 +1,15 @@
 #include "main.h"
 
 int main(){
-    cout<<"Hello World";
+    cout<<"Hello World"<<endl;
+    eigenExample();
     return 0;
 }
+
+void eigenExample(){
+    Eigen::MatrixXd m(2,2);
+    m(1,0) = 2.5;
+    m(0,1) = -1;
+    m(1,1) = m(1,0) + m(0,1);
+    cout << m << endl;
+}