xo-unit ++ docs ++ quantity arithmetic + example

example/ex_qty/ex_qty.cpp

@@ -0,0 +1,18 @@
+/* @file ex_qty.cpp */
+
+#include "xo/unit/quantity.hpp"
+#include "xo/unit/quantity_iostream.hpp"
+
+using namespace std;
+
+int
+main() {
+    using namespace xo::qty;
+    namespace u = xo::qty::u;
+
+    static_assert(u::meter.n_bpu() == 1);
+
+    //constexpr auto q = qty::meters(2) + u::meter;
+}
+
+/* end ex_qty.cpp */