Reduce language requirement for constexpr BID conversions

doc/decimal/conversions.adoc

@@ -29,27 +29,54 @@ struct uint128
 
 // ----- BID Conversions -----
 
-BOOST_DECIMAL_CXX20_CONSTEXPR std::uint32_t to_bid_d32(decimal32 val) noexcept;
+constexpr std::uint32_t to_bid_d32(decimal32 val) noexcept;
 
-BOOST_DECIMAL_CXX20_CONSTEXPR std::uint32_t to_bid_d32f(decimal32_fast val) noexcept;
+constexpr decimal32 from_bid_d32(std::uint32_t bits) noexcept;
 
-BOOST_DECIMAL_CXX20_CONSTEXPR std::uint64_t to_bid_d64(decimal64 val) noexcept;
+constexpr std::uint32_t to_bid_d32f(decimal32_fast val) noexcept;
 
-BOOST_DECIMAL_CXX20_CONSTEXPR std::uint64_t to_bid_d64f(decimal64_fast val) noexcept;
+constexpr decimal32_fast from_bid_d32f(std::uint32_t bits) noexcept;
 
-BOOST_DECIMAL_CXX20_CONSTEXPR detail::uint128 to_bid_d128(decimal128 val) noexcept;
+constexpr std::uint64_t to_bid_d64(decimal64 val) noexcept;
+
+constexpr decimal64 from_bid_d64(std::uint64_t bits) noexcept;
+
+constexpr std::uint64_t to_bid_d64f(decimal64_fast val) noexcept;
+
+constexpr decimal64_fast from_bid_d64f(std::uint64_t bits) noexcept;
+
+constexpr detail::uint128 to_bid_d128(decimal128 val) noexcept;
+
+constexpr decimal128 from_bid_d128(detail::uint128 bits) noexcept;
+
+// Automatic detection if your platform has built-in unsigned __int128 or not to enable/disable the overload
+#ifdef BOOST_DECIMAL_HAS_INT128
+
+constexpr decimal128 from_bid_d128(unsigned __int128 bits) noexcept;
+
+#endif // BOOST_DECIMAL_HAS_INT128
+
+constexpr detail::uint128 to_bid_d128f(decimal128_fast val) noexcept;
+
+constexpr decimal128 from_bid_d128f(detail::uint128 bits) noexcept;
+
+#ifdef BOOST_DECIMAL_HAS_INT128
+
+constexpr decimal128 from_bid_d128f(unsigned __int128 bits) noexcept;
+
+#endif // BOOST_DECIMAL_HAS_INT128
 
 template <typename T>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(T val) noexcept;
+constexpr auto to_bid(T val) noexcept;
 
 template <typename T = decimal32_fast>
-BOOST_DECIMAL_CXX20_CONSTEXPR T from_bid(std::uint32_t bits) noexcept;
+constexpr T from_bid(std::uint32_t bits) noexcept;
 
 template <typename T = decimal64_fast>
-BOOST_DECIMAL_CXX20_CONSTEXPR T from_bid(std::uint64_t bits) noexcept;
+constexpr T from_bid(std::uint64_t bits) noexcept;
 
 template <typename T = decimal128>
-BOOST_DECIMAL_CXX20_CONSTEXPR T from_bid(detail::uint128 bits) noexcept;
+constexpr T from_bid(detail::uint128 bits) noexcept;
 
 // ----- DPD Conversions -----
 

include/boost/decimal/bid_conversion.hpp

@@ -20,149 +20,162 @@ namespace decimal {
 #  pragma GCC diagnostic ignored "-Wconversion"
 #endif
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid_d32(decimal32 val) noexcept -> std::uint32_t
+constexpr auto to_bid_d32(decimal32 val) noexcept -> std::uint32_t
 {
-    const auto bits {detail::bit_cast<std::uint32_t>(val)};
-    return bits;
+    return val.bits_;
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid_d32(std::uint32_t bits) noexcept -> decimal32
+constexpr auto from_bid_d32(std::uint32_t bits) noexcept -> decimal32
 {
-    const auto val {detail::bit_cast<decimal32>(bits)};
-    return val;
+    return from_bits(bits);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid_d32f(decimal32_fast val) noexcept -> std::uint32_t
+constexpr auto to_bid_d32f(decimal32_fast val) noexcept -> std::uint32_t
 {
     const decimal32 compliant_val {val};
-    const auto bits {detail::bit_cast<std::uint32_t>(compliant_val)};
-    return bits;
+    return to_bid_d32(compliant_val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid_d32f(std::uint32_t bits) noexcept -> decimal32_fast
+constexpr auto from_bid_d32f(std::uint32_t bits) noexcept -> decimal32_fast
 {
-    const auto compliant_val {detail::bit_cast<decimal32>(bits)};
+    const auto compliant_val {from_bid_d32(bits)};
     const decimal32_fast val {compliant_val};
     return val;
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid_d64(decimal64 val) noexcept -> std::uint64_t
+constexpr auto to_bid_d64(decimal64 val) noexcept -> std::uint64_t
 {
-    const auto bits {detail::bit_cast<std::uint64_t>(val)};
-    return bits;
+    return val.bits_;
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid_d64(std::uint64_t bits) noexcept -> decimal64
+constexpr auto from_bid_d64(std::uint64_t bits) noexcept -> decimal64
 {
-    const auto val {detail::bit_cast<decimal64>(bits)};
-    return val;
+    return from_bits(bits);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid_d64f(decimal64_fast val) noexcept -> std::uint64_t
+constexpr auto to_bid_d64f(decimal64_fast val) noexcept -> std::uint64_t
 {
     const decimal64 compliant_val {val};
-    const auto bits {detail::bit_cast<std::uint64_t>(compliant_val)};
-    return bits;
+    return to_bid_d64(compliant_val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid_d64f(std::uint64_t bits) noexcept -> decimal64_fast
+constexpr auto from_bid_d64f(std::uint64_t bits) noexcept -> decimal64_fast
 {
-    const auto compliant_val {detail::bit_cast<decimal64>(bits)};
+    const auto compliant_val {from_bid_d64(bits)};
     const decimal64_fast val {compliant_val};
     return val;
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid_d128(decimal128 val) noexcept -> detail::uint128
+constexpr auto to_bid_d128(decimal128 val) noexcept -> detail::uint128
 {
-    const auto bits {detail::bit_cast<detail::uint128>(val)};
-    return bits;
+    return val.bits_;
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid_d128(detail::uint128 bits) noexcept -> decimal128
+constexpr auto from_bid_d128(detail::uint128 bits) noexcept -> decimal128
 {
-    const auto val {detail::bit_cast<decimal128>(bits)};
-    return val;
+    return from_bits(bits);
+}
+
+#ifdef BOOST_DECIMAL_HAS_INT128
+constexpr auto from_bits_d128(detail::uint128_t bits) noexcept -> decimal128
+{
+    return from_bits(bits);
 }
+#endif
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid_d128f(decimal128_fast val) noexcept -> detail::uint128
+constexpr auto to_bid_d128f(decimal128_fast val) noexcept -> detail::uint128
 {
     const decimal128 compliant_val {val};
-    const auto bits {detail::bit_cast<detail::uint128>(compliant_val)};
-    return bits;
+    return to_bid_d128(compliant_val);
+}
+
+constexpr auto from_bid_d128f(detail::uint128 bits) noexcept -> decimal128_fast
+{
+    const auto compliant_val {from_bid_d128(bits)};
+    const decimal128_fast val {compliant_val};
+    return val;
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid_d128f(detail::uint128 bits) noexcept -> decimal128_fast
+#ifdef BOOST_DECIMAL_HAS_INT128
+constexpr auto from_bid_d128f(detail::uint128_t bits) noexcept -> decimal128_fast
 {
-    const auto compliant_val {detail::bit_cast<decimal128>(bits)};
+    const auto compliant_val {from_bid_d128(bits)};
     const decimal128_fast val {compliant_val};
     return val;
 }
+#endif
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(decimal32 val) noexcept -> std::uint32_t
+constexpr auto to_bid(decimal32 val) noexcept -> std::uint32_t
 {
     return to_bid_d32(val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(decimal32_fast val) noexcept -> std::uint32_t
+constexpr auto to_bid(decimal32_fast val) noexcept -> std::uint32_t
 {
     return to_bid_d32f(val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(decimal64 val) noexcept -> std::uint64_t
+constexpr auto to_bid(decimal64 val) noexcept -> std::uint64_t
 {
     return to_bid_d64(val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(decimal64_fast val) noexcept -> std::uint64_t
+constexpr auto to_bid(decimal64_fast val) noexcept -> std::uint64_t
 {
     return to_bid_d64f(val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(decimal128 val) noexcept -> detail::uint128
+constexpr auto to_bid(decimal128 val) noexcept -> detail::uint128
 {
     return to_bid_d128(val);
 }
 
-BOOST_DECIMAL_CXX20_CONSTEXPR auto to_bid(decimal128_fast val) noexcept -> detail::uint128
+constexpr auto to_bid(decimal128_fast val) noexcept -> detail::uint128
 {
     return to_bid_d128f(val);
 }
 
+template <typename T>
+constexpr auto to_bid(T val) noexcept
+{
+    return to_bid(val);
+}
+
 template <typename T = decimal32_fast>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid(std::uint32_t bits) noexcept
+constexpr auto from_bid(std::uint32_t bits) noexcept
     BOOST_DECIMAL_REQUIRES(detail::is_decimal_floating_point_v, T)
 {
     return from_bid_d32f(bits);
 }
 
 template <>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid<decimal32>(std::uint32_t bits) noexcept -> decimal32
+constexpr auto from_bid<decimal32>(std::uint32_t bits) noexcept -> decimal32
 {
     return from_bid_d32(bits);
 }
 
 template <typename T = decimal64_fast>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid(std::uint64_t bits) noexcept
+constexpr auto from_bid(std::uint64_t bits) noexcept
     BOOST_DECIMAL_REQUIRES(detail::is_decimal_floating_point_v, T)
 {
     return from_bid_d64f(bits);
 }
 
 template <>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid<decimal64>(std::uint64_t bits) noexcept -> decimal64
+constexpr auto from_bid<decimal64>(std::uint64_t bits) noexcept -> decimal64
 {
     return from_bid_d64(bits);
 }
 
 template <typename T = decimal128_fast>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid(detail::uint128 bits) noexcept
+constexpr auto from_bid(detail::uint128 bits) noexcept
     BOOST_DECIMAL_REQUIRES(detail::is_decimal_floating_point_v, T)
 {
     return from_bid_d128f(bits);
 }
 
 template <>
-BOOST_DECIMAL_CXX20_CONSTEXPR auto from_bid<decimal128>(detail::uint128 bits) noexcept -> decimal128
+constexpr auto from_bid<decimal128>(detail::uint128 bits) noexcept -> decimal128
 {
     return from_bid_d128(bits);
 }

include/boost/decimal/decimal128.hpp

@@ -228,6 +228,14 @@ BOOST_DECIMAL_EXPORT class decimal128 final
 
     friend constexpr auto not_finite(decimal128 rhs) noexcept -> bool;
 
+    friend constexpr auto to_bid_d128(decimal128 val) noexcept -> detail::uint128;
+
+    friend constexpr auto from_bid_d128(detail::uint128 bits) noexcept -> decimal128;
+
+    #ifdef BOOST_DECIMAL_HAS_INT128
+    friend constexpr auto from_bid_d128(detail::uint128_t bits) noexcept -> decimal128;
+    #endif
+
 public:
     // 3.2.4.1 construct/copy/destroy
     constexpr decimal128() noexcept = default;

include/boost/decimal/decimal32.hpp

@@ -218,6 +218,10 @@ BOOST_DECIMAL_EXPORT class decimal32 final // NOLINT(cppcoreguidelines-special-m
     template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE DecimalType>
     friend constexpr auto sequential_less_impl(DecimalType lhs, DecimalType rhs) noexcept -> bool;
 
+    friend constexpr auto to_bid_d32(decimal32 val) noexcept -> std::uint32_t;
+
+    friend constexpr auto from_bid_d32(std::uint32_t bits) noexcept -> decimal32;
+
     template <typename DecimalType>
     friend constexpr auto to_dpd_d32(DecimalType val) noexcept
     BOOST_DECIMAL_REQUIRES_RETURN(detail::is_decimal_floating_point_v, DecimalType, std::uint32_t);

include/boost/decimal/decimal64.hpp

@@ -225,6 +225,10 @@ BOOST_DECIMAL_EXPORT class decimal64 final
     template <BOOST_DECIMAL_DECIMAL_FLOATING_TYPE DecimalType>
     friend constexpr auto sequential_less_impl(DecimalType lhs, DecimalType rhs) noexcept -> bool;
 
+    friend constexpr auto to_bid_d64(decimal64 val) noexcept -> std::uint64_t;
+
+    friend constexpr auto from_bid_d64(std::uint64_t bits) noexcept -> decimal64;
+
 public:
     // 3.2.3.1 construct/copy/destroy
     constexpr decimal64() noexcept = default;

test/test_bid_conversions.cpp

@@ -18,7 +18,7 @@ void test()
     for (std::size_t i {}; i < 1024; ++i)
     {
         const T val {dist(rng)};
-        const auto bits {to_bid(val)};
+        const auto bits {to_bid<T>(val)};
         const T return_val {from_bid<T>(bits)};
         BOOST_TEST_EQ(val, return_val);
     }