C++ Mathematical Expression Library (ExprTk)  https://www.partow.net/programming/exprtk/index.html
diff --git a/Makefile b/Makefile
index 4a1a20f..77422fd 100644
--- a/Makefile
+++ b/Makefile
@@ -42,6 +42,7 @@
 BUILD_LIST+=exprtk_simple_example_16
 BUILD_LIST+=exprtk_simple_example_17
 BUILD_LIST+=exprtk_simple_example_18
+BUILD_LIST+=exprtk_simple_example_19
 
 
 all: $(BUILD_LIST)