fuzzy floating point comparison with optional

include/xlnt/utils/optional.hpp

@@ -25,6 +25,7 @@
 
 #include <xlnt/xlnt_config.hpp>
 #include <xlnt/utils/exceptions.hpp>
+#include <detail/numeric_utils.hpp>
 #include <type_traits>
 
 namespace xlnt {
@@ -49,6 +50,23 @@ class optional
     using set_move_noexcept_t = typename std::conditional<std::is_nothrow_move_constructible<T>{} && std::is_nothrow_move_assignable<T>{}, std::true_type, std::false_type>::type;
     using clear_noexcept_t = typename std::conditional<std::is_nothrow_destructible<T>{}, std::true_type, std::false_type>::type;
 #endif
+    /// <summary>
+    /// Default equality operation, just uses operator==
+    /// </summary>
+    template <typename T, typename std::enable_if<!std::is_floating_point_v<T>>::type * = nullptr>
+    constexpr bool compare_equal(const T &lhs, const T &rhs) const
+    {
+        return lhs == rhs;
+    }
+
+    /// <summary>
+    /// equality operation for floating point numbers. Provides "fuzzy" equality
+    /// </summary>
+    template <typename T, typename std::enable_if<std::is_floating_point_v<T>>::type * = nullptr>
+    constexpr bool compare_equal(const T &lhs, const T &rhs) const
+    {
+        return detail::float_equals(lhs, rhs);
+    }
 
 public:
     /// <summary>
@@ -281,7 +299,8 @@ public:
         {
             return true;
         }
-        return value_ref() == other.value_ref();
+        // equality is overloaded to provide fuzzy equality when T is a fp number
+        return compare_equal(value_ref(), other.value_ref());
     }
 
     /// <summary>