isnan() returns 1 (true) if x is NaN (the IEEE floating-point
reserved Not-a-Number value) and 0 (false) otherwise.
Entry-Point Names
Generic
Function Data Type OpenVMS Tru64 UNIX
Name Required
isnan S_FLOAT math$isnan_s isnanf
T_FLOAT math$isnan_t isnan
X_FLOAT math$isnan_x isnanl
F_FLOAT math$isnan_f
G_FLOAT math$isnan_g