xo-unit: minor tweaks; add xo_ratio dep to build

CMakeLists.txt

@@ -51,7 +51,7 @@ xo_export_cmake_config(${PROJECT_NAME} ${PROJECT_VERSION} ${PROJECT_NAME}Targets
 # ----------------------------------------------------------------
 # dependencies
 
-#xo_headeronly_dependency(${SELF_LIB} randomgen)
+xo_headeronly_dependency(${SELF_LIB} xo_ratio)
 # etc..
 
 # end CMakeLists.txt

include/xo/unit/dim_util.hpp

@@ -2,12 +2,15 @@
 
 #pragma once
 
-
-#include "stringliteral.hpp"
+//#include "stringliteral.hpp"
+//#include "xo/flatstring/flatstring.hpp"
+#include <cstdint>
 
 namespace xo {
     namespace unit {
         enum class dim {
+            invalid = -1,
+
             /** weight.  native unit = 1 gram **/
             mass,
             /** distance.  native unit = 1 meter **/
@@ -23,8 +26,13 @@ namespace xo {
             currency,
             /** a screen price **/
             price,
+
+            /** comes last, counts entries **/
+            n_dim
         };
 
+        static constexpr std::size_t n_dim = static_cast<std::size_t>(dim::n_dim);
+
         enum class native_unit_id {
             gram,
             meter,
@@ -53,6 +61,7 @@ namespace xo {
 
         template <dim Dim>
         constexpr auto native_unit_for_v = native_unit_for<Dim>::value;
+
     } /*namespace unit*/
 } /*namespace xo*/