M.Metcalf et. al. の "fortran95/2003 explained" §11.2 によると、
"Within Fortran, -0 is treated as the ssame as a zero in all intrinsic operations and comparisons, but it can be detected by the 'sign' function and is respected on formatted output."
PROGRAM test IMPLICIT NONE PRINT *, SQRT(-0.0) STOP END PROGRAM test