std::acos,std::acosf,std::acosl (3) - Linux Manuals

std::acos,std::acosf,std::acosl: std::acos,std::acosf,std::acosl

NAME

std::acos,std::acosf,std::acosl - std::acos,std::acosf,std::acosl

Synopsis

Defined in header <cmath>
float acos ( float arg );
float acosf( float arg ); (since C++11)
double acos ( double arg ); (1) (2)
long double acos ( long double arg );
long double acosl( long double arg ); (3) (since C++11)
double acos ( IntegralType arg ); (4) (since C++11)

1-3) Computes the principal value of the arc cosine of arg.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to 2) (the argument is cast to double).

Parameters

arg - value of a floating-point or Integral_type

Return value

If no errors occur, the arc cosine of arg (arccos(arg)) in the range [0 , π], is returned.
If a domain error occurs, an implementation-defined value is returned (NaN where supported)
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.
Domain error occurs if arg is outside the range [-1.0, 1.0]
If the implementation supports IEEE floating-point arithmetic (IEC 60559),

* If the argument is +1, the value +0 is returned.
* If |arg| > 1, a domain error occurs and NaN is returned.
* if the argument is NaN, NaN is returned

Example

// Run this code

  #include <cmath>
  #include <iostream>
  #include <cerrno>
  #include <cfenv>
  #include <cstring>

  #pragma STDC FENV_ACCESS ON
  int main()
  {
      std::cout << "acos(-1) = " << acos(-1) << '\n'
                << "acos(0.0) = " << acos(0.0) << " 2*acos(0.0) = " << 2*acos(0) << '\n'
                << "acos(0.5) = " << acos(0.5) << " 3*acos(0.5) = " << 3*acos(0.5) << '\n'
                << "acos(1) = " << acos(1) << '\n';
      // error handling
      errno = 0;
      std::feclearexcept(FE_ALL_EXCEPT);
      std::cout << "acos(1.1) = " << acos(1.1) << '\n';
      if (errno == EDOM)
          std::cout << " errno == EDOM: " << std::strerror(errno) << '\n';
      if (std::fetestexcept(FE_INVALID))
          std::cout << " FE_INVALID raised" << '\n';
  }

Output:

  acos(-1) = 3.14159
  acos(0.0) = 1.5708 2*acos(0.0) = 3.14159
  acos(0.5) = 1.0472 3*acos(0.5) = 3.14159
  acos(1) = 0
  acos(1.1) = nan
      errno == EDOM: Numerical argument out of domain
      FE_INVALID raised