refactor: More stream-specific implementation moved to quantity_io.h

src/include/units/bits/unit_text.h

@@ -26,7 +26,6 @@
 #include <units/bits/external/text_tools.h>
 #include <units/prefix.h>
 #include <units/derived_dimension.h>
-#include <sstream>
 
 namespace units::detail {
 
@@ -178,14 +177,4 @@ constexpr auto unit_text()
   }
 }
 
-template<typename CharT, class Traits, typename D, typename U, typename Rep>
-void to_stream(std::basic_ostream<CharT, Traits>& os, const quantity<D, U, Rep>& q)
-{
-  os << q.count();
-  constexpr auto symbol = detail::unit_text<D, U>();
-  if constexpr (symbol.standard().size()) {
-    os << " " << symbol.standard();
-  }
-}
-
 }  // namespace units::detail

src/include/units/quantity.h

@@ -30,7 +30,6 @@
 #include <units/generic/dimensionless.h>
 #include <units/quantity_cast.h>
 #include <compare>
-#include <ostream>
 
 namespace units {
 

src/include/units/quantity_io.h

@@ -25,9 +25,24 @@
 
 #include <units/bits/external/fixed_string_io.h>
 #include <units/quantity.h>
+#include <sstream>
 
 namespace units {
 
+namespace detail {
+
+template<typename CharT, class Traits, typename D, typename U, typename Rep>
+void to_stream(std::basic_ostream<CharT, Traits>& os, const quantity<D, U, Rep>& q)
+{
+  os << q.count();
+  constexpr auto symbol = detail::unit_text<D, U>();
+  if constexpr (symbol.standard().size()) {
+    os << " " << symbol.standard();
+  }
+}
+
+} //  namespace detail
+
 template<typename CharT, typename Traits, typename D, typename U, typename Rep>
 std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os, const quantity<D, U, Rep>& q)
   requires requires { os << q.count(); }