At Monday 2005-04-18 03:52, you wrote:
Currently "functional/hash - hash_float_test" fails on Tru64/CXX6.5 (See http://tinyurl.com/8opfo)
The reason of the failure is that QNaN and 0 give the same hash code on this platform. I was wondering what the expected hash of QNAN actually should be. Is it some platform dependent value?
Am I missing something here? Since it is obvious that one canNOT generate a unique hash for all possible inputs, why should there necessarily be a difference between any 2?
I put some traces in hash_detail::float_hash_value(), and the cause for the same hash value for 0 and QNAN seems to be that static_cast<int>(QNAN) gives 0 which then results in a call of hash_combine(0, 0) for both 0 and QNAN.
Does anybody know what the expected result of static_cast<int>(QNAN) is? My guess is that either I should get a floating point exception for this expression or that the return value is unspecified and errno is set to [EDOM], but this is pure speculation on my side.
Markus
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