<math.h>
and <complex.h>
that return floating-point
results (5.2.4.2.2).
FLT_ROUNDS
(5.2.4.2.2).
FLT_EVAL_METHOD
(5.2.4.2.2).
FP_CONTRACT
pragma (6.5).
FENV_ACCESS
pragma (7.6.1).
FP_CONTRACT
pragma (7.12.2).