Hi, Boost.Math had some changes on trunk a few months ago, on the implementation of signbit, to fix the invalid result of signbit(-NaN) (fixed by using Johan Rade's fp_traits library). Currently, in order to work with multiple Boost releases, Spirit2x uses: - a custom version of signbit when compiled against an older Boost release, - the Boost.Math implementation when compiled against Boost 1.39 or later (on the assumption that those changes will be in Boost 1.39). But looking at the schedule sent by Beman, we're nearing the 1.39 beta (some time this week), and those changes have not been merged to release branch. I was wondering, is it planned to merge them for 1.39, or will it only be done in a later release? Thanks, François