John Maddock wrote:
Johan Råde wrote:
This can be templatized, and will handle such things as 80-bit long double.
Maybe, don't forget the padding bytes that are often injected into such types (only an issue if the endianness put's the sign bit at the end of the 10-byte sequence rather than the beginning).
John.
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John, I think the following is a reasonable compromise: const boost::uint32_t signbit_mask = binary_cast<boost::uint32_t>(1.0f) ^ binary_cast<boost::uint32_t>(-1.0f); inline bool signbit_impl(float x) { return binary_cast<boost::uint32_t>(x) & signbit_mask; } inline bool signbit_impl(double x) { return sign_bit(static_cast<float>(x)); } inline bool signbit_impl(long double x) { return sign_bit(static_cast<float>(x)); } Here I assume that 1. IEEE 754 or some similar representation 2. sizeof(float) == 4 3. casts between different numeric types preserve the sign bits, also for non-finite numbers. That should cover a large number of platforms. --Johan Råde