"int isinf(double "value);
"int isnan(double "value);
"int finite(double "value);
The isnan() function returns a non-zero value if value is "not-a-number" (NaN), and 0 otherwise.
The finite() function returns a non-zero value if value is neither infinite nor a "not-a-number" (NaN) value, and 0 otherwise.
