std::atan, std::atanf, std::atanl

Since C++26

Header: <cmath>

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)

# Declarations

float atan ( float num );
double atan ( double num );
long double atan ( long double num );

(until C++23)

/*floating-point-type*/
atan ( /*floating-point-type*/ num );

(since C++23) (constexpr since C++26)

float atanf( float num );

(since C++11) (constexpr since C++26)

long double atanl( long double num );

(since C++11) (constexpr since C++26)

SIMD overload (since C++26)

template< /*math-floating-point*/ V >
constexpr /*deduced-simd-t*/<V>
atan ( const V& v_num );

(since C++26)

Additional overloads (since C++11)

template< class Integer >
double atan ( Integer num );

(constexpr since C++26)

# Parameters

num: floating-point or integer value

# Return value

If a range error occurs due to underflow, the correct result (after rounding) 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 (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(num)).

# Example

#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';
}