Atan
Defined in header <cmath>
.
Description
Computes the principal value of the arc tangent of num
.
The library provides overloads of std::atan for all cv-unqualified floating-point types as the type of the parameter num
(od C++23).
Additional Overloads are provided for all integer types, which are treated as double (od C++11).
Declarations
- C++23
- C++11
// 1)
/* floating-point-type */ atan( /* floating-point-type */ num );
// 2)
float atanf( float num );
// 3)
long double atanl( long double num );
// 4)
template< class Integer >
double atan ( Integer num );
// 1)
float atan ( float num );
// 2)
double atan ( double num );
// 3)
long double atan ( long double num );
// 4)
float atanf( float num );
// 5)
long double atanl( long double num );
// 6)
template< class Integer >
double atan ( Integer num );
Parameters
num
- floating-point or integer value
Return value
If no errors occur, the arc tangent of num
(arctan(num)) in the range [-π/2, π/2]
radians, is returned.
If a range error occurs due to underflow, the correct result (after rounding) is returned.
Error handling
Errors are reported as specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559):
If the argument is ±0
, it is returned unmodified
If the argument is +∞
, +π/2
is returned
If the argument is -∞
, -π/2
is returned
if the argument is NaN, NaN is returned
Notes
POSIX
specifies that in case of underflow, num
is returned unmodified,
and if that is not supported, an implementation-defined value no greater than DBL_MIN
, FLT_MIN
, and LDBL_MIN
is returned.
The additional overloads are not required to be provided exactly as Additional Overloads.
They only need to be sufficient to ensure that for their argument num of integer type,
std::atan(num)
has the same effect as std::atan(static_cast<double>(num))
.
Examples
#include <cmath>
#include <iostream>
int main()
{
std::cout
<< "atan(1) = "
<< atan(1) << '\n'
<< "4*atan(1) = "
<< 4 * atan(1) << '\n';
// special values
std::cout
<< "atan(Inf) = "
<< atan(INFINITY) << '\n'
<< "2*atan(Inf) = "
<< 2 * atan(INFINITY) << '\n'
<< "atan(-0.0) = "
<< atan(-0.0) << '\n'
<< "atan(+0.0) = "
<< atan(0) << '\n';
}
atan(1) = 0.785398
4*atan(1) = 3.14159
atan(Inf) = 1.5708
2*atan(Inf) = 3.14159
atan(-0.0) = -0
atan(+0.0) = 0