[libcxx-commits] [libcxx] [libc++] simplify the midpoint function (PR #81717)

[via libcxx-commits]

https://github.com/rilysh updated https://github.com/llvm/llvm-project/pull/81717

>From 6f38fc2c896a14db13ae440d48ec3dc114ae9faf Mon Sep 17 00:00:00 2001
From: rilysh <nightquick at proton.me>
Date: Wed, 14 Feb 2024 14:57:11 +0530
Subject: [PATCH 1/2] [libc++] simplify the midpoint function

Right now we've a nested ternary for the midpoint function, but this
can be simplified a bit more, using if..else. This also slightly
increases the readability of that function.
---
 libcxx/include/__numeric/midpoint.h | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/libcxx/include/__numeric/midpoint.h b/libcxx/include/__numeric/midpoint.h
index 5d715c21d8eaca..4232610ce27be4 100644
--- a/libcxx/include/__numeric/midpoint.h
+++ b/libcxx/include/__numeric/midpoint.h
@@ -67,14 +67,16 @@ template <class _Fp>
 _LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_floating_point_v<_Fp>, _Fp> midpoint(_Fp __a, _Fp __b) noexcept {
   constexpr _Fp __lo = numeric_limits<_Fp>::min() * 2;
   constexpr _Fp __hi = numeric_limits<_Fp>::max() / 2;
-  return std::__fp_abs(__a) <= __hi && std::__fp_abs(__b) <= __hi
-           ? // typical case: overflow is impossible
-             (__a + __b) / 2
-           :                                             // always correctly rounded
-             std::__fp_abs(__a) < __lo ? __a + __b / 2 : // not safe to halve a
-                 std::__fp_abs(__b) < __lo ? __a / 2 + __b
-                                           : // not safe to halve b
-                 __a / 2 + __b / 2;          // otherwise correctly rounded
+
+  // typical case: overflow is impossible
+  if (std::__fp_abs(__a) <= __hi && std::__fp_abs(__b) <= __hi)
+    return (__a + __b) / 2; // always correctly rounded
+  else if (std::__fp_abs(__a) < __lo)
+    return __a + __b / 2; // not safe to halve a
+  else if (std::__fp_abs(__b) < __lo)
+    return __a / 2 + __b; // not safe to halve b
+  else
+    return __a / 2 + __b / 2; // otherwise correctly rounded
 }
 
 #endif // _LIBCPP_STD_VER >= 20

>From 366b1d82c6370f77aa02356ed037e23f0a53ecb9 Mon Sep 17 00:00:00 2001
From: rilysh <nightquick at proton.me>
Date: Fri, 16 Feb 2024 00:47:51 +0530
Subject: [PATCH 2/2] [libc++] midpoint.h: use LLVM style condition block

---
 libcxx/include/__numeric/midpoint.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libcxx/include/__numeric/midpoint.h b/libcxx/include/__numeric/midpoint.h
index 4232610ce27be4..5ef30d4ec50f5a 100644
--- a/libcxx/include/__numeric/midpoint.h
+++ b/libcxx/include/__numeric/midpoint.h
@@ -71,12 +71,12 @@ _LIBCPP_HIDE_FROM_ABI constexpr enable_if_t<is_floating_point_v<_Fp>, _Fp> midpo
   // typical case: overflow is impossible
   if (std::__fp_abs(__a) <= __hi && std::__fp_abs(__b) <= __hi)
     return (__a + __b) / 2; // always correctly rounded
-  else if (std::__fp_abs(__a) < __lo)
+  if (std::__fp_abs(__a) < __lo)
     return __a + __b / 2; // not safe to halve a
-  else if (std::__fp_abs(__b) < __lo)
+  if (std::__fp_abs(__b) < __lo)
     return __a / 2 + __b; // not safe to halve b
-  else
-    return __a / 2 + __b / 2; // otherwise correctly rounded
+
+  return __a / 2 + __b / 2; // otherwise correctly rounded
 }
 
 #endif // _LIBCPP_STD_VER >= 20