diff --git a/example/CMakeLists.txt b/example/CMakeLists.txt
index 06512248..7f8eb99d 100644
--- a/example/CMakeLists.txt
+++ b/example/CMakeLists.txt
@@ -10,6 +10,7 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON CACHE INTERNAL "")
 add_subdirectory(ex1)
 add_subdirectory(ex2)
 add_subdirectory(ex3)
+add_subdirectory(ex4)
 
 # ----------------------------------------------------------------
 # make standard directories for std:: includes explicit
diff --git a/example/ex4/CMakeLists.txt b/example/ex4/CMakeLists.txt
new file mode 100644
index 00000000..02c1f301
--- /dev/null
+++ b/example/ex4/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_executable(ex4 ex4.cpp)
+xo_include_options(ex4)
diff --git a/example/ex4/ex4.cpp b/example/ex4/ex4.cpp
new file mode 100644
index 00000000..82e361db
--- /dev/null
+++ b/example/ex4/ex4.cpp
@@ -0,0 +1,44 @@
+/* @file ex4.cpp */
+
+#include "indentlog/scope.hpp"
+
+using namespace xo;
+
+class Quadratic {
+public:
+    Quadratic(double a, double b, double c) : a_{a}, b_{b}, c_{c} {}
+
+    double operator() (double x) const {
+        scope log(XO_ENTER0(info), tag("a", a_), xtag("b", b_), xtag("c", c_), xtag("x", x));
+
+        double retval = (a_ * x * x) + (b_ * x) + c_;
+
+        log.end_scope("<-", xtag("retval", retval));
+
+        return retval;
+    }
+
+private:
+    double a_ = 0.0;;
+    double b_ = 0.0;
+    double c_ = 0.0;
+};
+
+int
+main(int argc, char ** argv) {
+    //log_config::style  = FS_Pretty;
+    log_config::style  = FS_Streamlined;
+    log_config::min_log_level = log_level::info;
+
+    scope log(XO_ENTER0(info));
+
+    Quadratic quadratic(2.0, -5.0, 7.0);
+
+    double x = 3.0;
+    double r = quadratic(3.0);
+
+    log && log(tag("x", x));
+    log && log("<-", xtag("quadratic(x)", r));
+}
+
+/* end ex4.cpp */