From 880528e5ca93da0159a3591582c7c125d461d19b Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Fri, 18 Oct 2019 22:34:43 +0200
Subject: [PATCH] Compile-time performance of printing a prefix improved

---
 src/include/units/format.h | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/include/units/format.h b/src/include/units/format.h
index 4fde18a3..6728eeb3 100644
--- a/src/include/units/format.h
+++ b/src/include/units/format.h
@@ -47,16 +47,17 @@ namespace units {
     void print_prefix_or_ratio(std::basic_ostream<CharT, Traits>& os)
     {
       if constexpr(Ratio::num != 1 || Ratio::den != 1) {
-        using prefix = downcast_target<detail::prefix_base<PrefixType, Ratio>>;
+        if(!std::same_as<PrefixType, no_prefix>) {
+          using prefix = downcast_target<detail::prefix_base<PrefixType, Ratio>>;
 
-        if constexpr(!std::same_as<prefix, prefix_base<PrefixType, Ratio>>) {
-          // print as a prefixed unit
-          os << prefix::symbol;
-        }
-        else {
-          // print as a ratio of the coherent unit
-          print_ratio<Ratio>(os);
+          if constexpr(!std::same_as<prefix, prefix_base<PrefixType, Ratio>>) {
+            // print as a prefixed unit
+            os << prefix::symbol;
+            return;
+          }
         }
+        // print as a ratio of the coherent unit
+        print_ratio<Ratio>(os);
       }
     }