atan
Synopsis
#include <math.h>
double atan(double x);
float atanf(float x);
long double atanl(long double x);
Status
Partially implemented
Conformance
IEEE Std 1003.1-2017
Description
These functions shall compute the principal value of the arc tangent of their argument x.
An application wishing to check for error situations should set errno
to zero and call feclearexcept(FE_ALL_EXCEPT)
before calling these functions. On return, if errno
is non-zero or
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.
Return value
Upon successful completion, these functions shall return the arc tangent of x in the range [-PI/2,PI/2]
radians.
-
If x is
NaN
, aNaN
shall be returned. -
If x is
±0
, x shall be returned. -
If x is
±Inf
,±/2
shall be returned. -
If x is subnormal, a range error may occur and x should be returned.
-
If x is not returned,
atan()
,atanf()
, andatanl()
shall return an implementation-defined value no greater in magnitude thanDBL_MIN
,FLT_MIN
, andLDBL_MIN
, respectively.
Errors
These functions may fail if:
- Range Error
The value of x is subnormal.
If the integer expression (math_errhandling & MATH_ERRNO)
is non-zero, then errno
shall be set to ERANGE
. If the
integer expression (math_errhandling & MATH_ERREXCEPT)
is non-zero, then the underflow floating-point
exception shall be raised.
Tests
Untested
Known bugs
None