Fix fast comparison of zero

mborland · mborland · commit 8a49018933d4 · 2025-06-30T09:52:14.000-04:00
diff --git a/include/boost/decimal/detail/comparison.hpp b/include/boost/decimal/detail/comparison.hpp
@@ -101,6 +101,12 @@ BOOST_DECIMAL_FORCE_INLINE constexpr auto equality_impl(DecimalType lhs, Decimal
 template <BOOST_DECIMAL_FAST_DECIMAL_FLOATING_TYPE DecimalType>
 BOOST_DECIMAL_FORCE_INLINE constexpr auto fast_equality_impl(const DecimalType& lhs, const DecimalType& rhs) noexcept -> bool
 {
+    if (lhs.significand_ == 0U && rhs.significand_ == 0U)
+    {
+        // -0 == +0
+        return true;
+    }
+
     if (lhs.exponent_ != rhs.exponent_)
     {
         return false;
@@ -117,11 +123,6 @@ BOOST_DECIMAL_FORCE_INLINE constexpr auto fast_equality_impl(const DecimalType&
     }
     #endif
 
-    if (lhs.significand_ == 0U)
-    {
-        return true; // -0 == +0
-    }
-
     return lhs.sign_ == rhs.sign_;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -101,6 +101,12 @@ BOOST_DECIMAL_FORCE_INLINE constexpr auto equality_impl(DecimalType lhs, Decimal`
`101`	`101`	`template <BOOST_DECIMAL_FAST_DECIMAL_FLOATING_TYPE DecimalType>`
`102`	`102`	`BOOST_DECIMAL_FORCE_INLINE constexpr auto fast_equality_impl(const DecimalType& lhs, const DecimalType& rhs) noexcept -> bool`
`103`	`103`	`{`
	`104`	`+ if (lhs.significand_ == 0U && rhs.significand_ == 0U)`
	`105`	`+ {`
	`106`	`+ // -0 == +0`
	`107`	`+ return true;`
	`108`	`+ }`
	`109`	`+`
`104`	`110`	`if (lhs.exponent_ != rhs.exponent_)`
`105`	`111`	`{`
`106`	`112`	`return false;`
`@@ -117,11 +123,6 @@ BOOST_DECIMAL_FORCE_INLINE constexpr auto fast_equality_impl(const DecimalType&`
`117`	`123`	`}`
`118`	`124`	`#endif`
`119`	`125`
`120`		`- if (lhs.significand_ == 0U)`
`121`		`- {`
`122`		`- return true; // -0 == +0`
`123`		`- }`
`124`		`-`
`125`	`126`	`return lhs.sign_ == rhs.sign_;`
`126`	`127`	`}`
`127`	`128`