Index: boost/math/special_functions/atanh.hpp =================================================================== --- boost/math/special_functions/atanh.hpp (revision 80676) +++ boost/math/special_functions/atanh.hpp (working copy) @@ -61,17 +61,17 @@ // -Infinity: return -policies::raise_overflow_error(function, 0, pol); } - else if(x > 1 - tools::epsilon()) - { - // Infinity: - return policies::raise_overflow_error(function, 0, pol); - } else if(x > 1) { return policies::raise_domain_error( function, "atanh requires x <= 1, but got x = %1%.", x, pol); } + else if(x > 1 - tools::epsilon()) + { + // Infinity: + return policies::raise_overflow_error(function, 0, pol); + } else if(abs(x) >= tools::forth_root_epsilon()) { // http://functions.wolfram.com/ElementaryFunctions/ArcTanh/02/