From a11f5a92b6b5f914b35192abb233ee7edd256843 Mon Sep 17 00:00:00 2001
From: Jan Sende <44576417+jansende@users.noreply.github.com>
Date: Mon, 30 Sep 2019 23:38:33 +0200
Subject: [PATCH] Optimized floating point unit conversions

- Divisions are now made at compile time.
- Only runtime multiplications are left.
---
 src/include/units/quantity.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index 3c5a803a..beb137cb 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -89,6 +89,14 @@ namespace units {
     template<typename To, typename CR, typename CRep, bool NumIsOne = false, bool DenIsOne = false>
     struct quantity_cast_impl {
       template<typename Q>
+      requires treat_as_floating_point<CRep>
+      static constexpr To cast(const Q& q)
+      {
+        return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * (static_cast<CRep>(CR::num) /
+                                       static_cast<CRep>(CR::den))));
+      }
+      template<typename Q>
+      requires !treat_as_floating_point<CRep>
       static constexpr To cast(const Q& q)
       {
         return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CR::num) /
@@ -108,6 +116,13 @@ namespace units {
     template<typename To, typename CR, typename CRep>
     struct quantity_cast_impl<To, CR, CRep, true, false> {
       template<Quantity Q>
+      requires treat_as_floating_point<CRep>
+      static constexpr To cast(const Q& q)
+      {
+        return To(static_cast<To::rep>(static_cast<CRep>(q.count()) * (CRep{1} / static_cast<CRep>(CR::den))));
+      }
+      template<Quantity Q>
+      requires !treat_as_floating_point<CRep>
       static constexpr To cast(const Q& q)
       {
         return To(static_cast<To::rep>(static_cast<CRep>(q.count()) / static_cast<CRep>(CR::den)));