Determines whether a floating-point value is an infinity.

int isinf(
   /* floating-point */ x
); /* C-only macro */

template <class FloatingType>
inline bool isinf(
   FloatingType x
) throw(); /* C++-only template function */

x
The floating-point value to test.

isinf returns a nonzero value (true in C++ code) if the argument x is a positive or negative infinity. isinf returns 0 (false in C++ code) if the argument is finite or a NAN. Both normal and subnormal floating-point values are considered finite.

isinf is a macro when compiled as C, and an inline template function when compiled as C++.

For more compatibility information, see Compatibility.

Math and floating-point support
fpclassify
_fpclass, _fpclassf
isfinite, _finite, _finitef
isnan, _isnan, _isnanf
isnormal