Added optional type.

Author: 5cript

CMakeLists.txt

@@ -6,6 +6,12 @@ project(interval-tree)
 
 add_library(interval-tree INTERFACE)
 
+if(INT_TREE_USE_OPTIONAL_POLYFILL)
+    target_compile_definitions(interval-tree INTERFACE
+        -DINTERVAL_TREE_USE_OPTIONAL_POLYFILL
+    )
+endif()
+
 target_include_directories(interval-tree INTERFACE ./include)
 
 if(INT_TREE_DRAW_EXAMPLES)

cmake/options.cmake

@@ -1,2 +1,4 @@
 option(INT_TREE_DRAW_EXAMPLES "Draws some examples in a subdirectory. run make_drawable.sh before this" OFF)
-option(INT_TREE_ENABLE_TESTS "Enable tests?" OFF)
+option(INT_TREE_ENABLE_TESTS "Enable tests?" OFF)
+# You generally do not want to turn this on, unless you are testing the library.
+option(INT_TREE_USE_OPTIONAL_POLYFILL "Use optional polyfill?" OFF)