Prefixed units support redesigned

src/include/units/quantity.h

@@ -23,7 +23,8 @@
 #pragma once
 
 #include <units/bits/concepts.h>
-#include <units/prefix.h>
+#include <units/unit.h>
+#include <units/format.h>
 #include <limits>
 #include <ostream>
 
@@ -283,7 +284,7 @@ namespace units {
       os << q.count() << " ";
       if constexpr(!detail::is_unit<quantity::unit>) {
         // print user-defined unit
-        os << unit::symbol::c_str();
+        os << unit::symbol;
       }
       else {
         using ratio = quantity::unit::ratio;
@@ -291,8 +292,8 @@ namespace units {
         if constexpr(!detail::is_dimension<dim>) {
           // print as a prefix or ratio of a coherent unit symbol defined by the user
           using coherent_unit = downcast_target<units::unit<dim, units::ratio<1>>>;
-          detail::print_prefix_or_ratio<ratio, typename coherent_unit::prefix>(os);
-          os << coherent_unit::symbol::c_str();
+          detail::print_prefix_or_ratio<ratio, typename coherent_unit::prefix_type>(os);
+          os << coherent_unit::symbol;
         }
         else {
           // print as a ratio of a coherent unit