id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
8809	pow(cpp_dec_float_type(-1), cpp_dec_float_type(n)) != (+-)1 for n >= 0x8000000000000000u	Jan Bouwer <JBouwer@…>	John Maddock	"Function ''pow(const number-or-expression-template-type&, const number-or-expression-template-type&)'' for ''cpp_dec_float'' backend gives wrong answer when used with base -1 and a positive exponent equivalent to a type (unsigned 64bit on my platform) with the high bit set;
i.e. an exponent >= 0x8000000000000000u.

The answers suggest that the exponent may be interpreted as its 2's complement-negative value (not confirmed) - see sample output below.
This may be related to #8711 & #8798.

Output from attached code:
{{{
pow(-1, 9.22337e+18) = -0.00127263
pow(-1, 9.22337e+18) = -0.00127263
pow(-1, 1.84467e+19) = 0
pow(-1, 1.84467e+19) = 0
pow(-1, 9.22337e+18) = -0.00127263
pow(-1, 9.22337e+18) = -0.00127263
pow(-1, 1.84467e+19) = 0
pow(-1, 1.84467e+19) = 0
}}}

Tested against trunk rev 8490 with clang (Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)) target: x86_64-apple-darwin12.4.0 with: -std=c++11 -stdlib=libc++.
"	Bugs	closed	To Be Determined	multiprecision	Boost Development Trunk	Problem	fixed		pbristow@… e_float@…