macro/function
<cmath> <ctgmath>

# isinf

macro ```isinf(x) ```
function ```bool isinf (float x); bool isinf (double x); bool isinf (long double x);```
Is infinity
Returns whether x is an infinity value (either positive infinity or negative infinity).

In C, this is implemented as a macro that returns an `int` value. The type of x shall be `float`, `double` or `long double`.
In C++, it is implemented with function overloads for each floating-point type, each returning a `bool` value.

### Parameters

x
A floating-point value.

### Return value

A non-zero value (`true`) if x is an infinity; and zero (`false`) otherwise.

### Example

 ``123456789101112`` ``````/* isinf example */ #include /* printf */ #include /* isinf, sqrt */ int main() { printf ("isinf(0.0) : %d\n",isinf(0.0)); printf ("isinf(1.0/0.0) : %d\n",isinf(1.0/0.0)); printf ("isinf(-1.0/0.0) : %d\n",isinf(-1.0/0.0)); printf ("isinf(sqrt(-1.0)): %d\n",isinf(sqrt(-1.0))); return 0; }``````

Output:
 ``` isinf(0.0) : 0 isinf(1.0/0.0) : 1 isinf(-1.0/0.0) : 1 isinf(sqrt(-1.0): 0 ```