std::atan, std::atanf, std::atanl
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Defined in header
<cmath>
(1)
float atan ( float num );
(until C++23)
double atan ( double num );
/*floating-point-type*/
atan ( /*floating-point-type*/ num );
(since C++23) atan ( /*floating-point-type*/ num );
(constexpr since C++26)
float atanf( float num );
(2)
(since C++11) (constexpr since C++26)
long double atanl( long double num );
(3)
(since C++11) (constexpr since C++26)
SIMD overload (since C++26)
Defined in header
<simd>
template< /*math-floating-point*/ V >
(S)
(since C++26)
constexpr /*deduced-simd-t*/<V>
Additional overloads (since C++11)
Defined in header
<cmath>
template< class Integer >
double atan ( Integer num );
(A)
(constexpr since C++26)
double atan ( Integer num );
1-3) 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.(since C++23)S) The SIMD overload performs an element-wise
std::atan on v_num.- (See math-floating-point and deduced-simd-t for their definitions.)
A) Additional overloads are provided for all integer types, which are treated as double.
(since C++11)[edit] Parameters
num
-
floating-point or integer value
[edit] 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.
[edit] 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.
[edit] 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 (A). 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)).
[edit] Example
Run this code
#include <cmath> #include <iostream> int main() { std::cout << "atan(1) = " << std::atan(1) << '\n' << "4*atan(1) = " << 4 * std::atan(1) << '\n'; // special values std::cout << "atan(Inf) = " << std::atan(INFINITY ) << '\n' << "2*atan(Inf) = " << 2 * std::atan(INFINITY ) << '\n' << "atan(-0.0) = " << std::atan(-0.0) << '\n' << "atan(+0.0) = " << std::atan(0) << '\n'; }
Output:
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
[edit] See also
(C++11)
(function template) [edit]
C documentation for atan