Merge pull request #1782 from evoskuil/master

Add bool to_integer(Integer& out, Float value).

Author: evoskuil

include/bitcoin/system/impl/math/cast.ipp

@@ -19,6 +19,7 @@
 #ifndef LIBBITCOIN_SYSTEM_MATH_CAST_IPP
 #define LIBBITCOIN_SYSTEM_MATH_CAST_IPP
 
+#include <cmath>
 #include <bitcoin/system/define.hpp>
 
 namespace libbitcoin {
@@ -209,6 +210,30 @@ constexpr Unsigned to_unsigned(Unsigned value) NOEXCEPT
 // Floating point casts.
 // ----------------------------------------------------------------------------
 
+template <typename Integer, typename Float,
+    if_integral_integer<Integer>,
+    if_floating_point<Float>>
+constexpr bool to_integer(Integer& out, Float value) NOEXCEPT
+{
+    if (!std::isfinite(value))
+        return false;
+
+    Float integer{};
+    const Float fractional = std::modf(value, &integer);
+    if (fractional != 0.0)
+        return false;
+
+    if (integer > static_cast<Float>(std::numeric_limits<Integer>::max()) ||
+        integer < static_cast<Float>(std::numeric_limits<Integer>::min()))
+        return false;
+
+    // Floating point conversion in c++ requires explicit or implicit cast.
+    BC_PUSH_WARNING(NO_CASTS_FOR_ARITHMETIC_CONVERSION)
+    out = static_cast<Integer>(integer);
+    BC_POP_WARNING()
+    return true;
+}
+
 template <typename Integer, typename Float,
     if_integral_integer<Integer>,
     if_floating_point<Float>>

include/bitcoin/system/math/cast.hpp

@@ -142,6 +142,12 @@ constexpr Unsigned to_unsigned(Unsigned value) NOEXCEPT;
 /// Floating point casts.
 /// ---------------------------------------------------------------------------
 
+/// Cast floating point to integral integer, overflow guarded.
+template <typename Integer = size_t, typename Float,
+    if_integral_integer<Integer> = true,
+    if_floating_point<Float> = true>
+constexpr bool to_integer(Integer& out, Float value) NOEXCEPT;
+
 /// Cast floating point to integral integer, overflow unguarded.
 template <typename Integer = size_t, typename Float,
     if_integral_integer<Integer> = true,