std::exp2, std::exp2f, std::exp2l - cppreference.com (original) (raw)

Defined in header
(1)
float exp2 ( float num ); double exp2 ( double num ); long double exp2 ( long double num );		(until C++23)
/floating-point-type/ exp2 ( /floating-point-type/ num );		(since C++23) (constexpr since C++26)
float exp2f( float num );	(2)	(since C++11) (constexpr since C++26)
long double exp2l( long double num );	(3)	(since C++11) (constexpr since C++26)
SIMD overload (since C++26)
Defined in header
template< /math-floating-point/ V > constexpr /deduced-simd-t/<V> exp2 ( const V& v_num );	(S)	(since C++26)
Additional overloads (since C++11)
Defined in header
template< class Integer > double exp2 ( Integer num );	(A)	(constexpr since C++26)

1-3) Computes 2 raised to the given power num. The library provides overloads of std::exp2 for all cv-unqualified floating-point types as the type of the parameter.(since C++23)

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 base-2 exponential of num (2num
) is returned.

If a range error due to overflow occurs, +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL 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, 1 is returned.
If the argument is -∞, +0 is returned.
If the argument is +∞, +∞ is returned.
If the argument is NaN, NaN is returned.

[edit] Notes

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::exp2(num) has the same effect as std::exp2(static_cast<double>(num)).

For integral exponents, it may be preferable to use std::ldexp.

[edit] Example

#include #include #include #include #include // #pragma STDC FENV_ACCESS ON int main() { std::cout << "exp2(4) = " << std::exp2(4) << '\n' << "exp2(0.5) = " << std::exp2(0.5) << '\n' << "exp2(-4) = " << std::exp2(-4) << '\n'; // special values std::cout << "exp2(-0) = " << std::exp2(-0.0) << '\n' << "exp2(-Inf) = " << std::exp2(-INFINITY) << '\n'; // error handling errno = 0; std::feclearexcept(FE_ALL_EXCEPT); const double inf = std::exp2(1024); const bool is_range_error = errno == ERANGE; std::cout << "exp2(1024) = " << inf << '\n'; if (is_range_error) std::cout << " errno == ERANGE: " << std::strerror(ERANGE) << '\n'; if (std::fetestexcept(FE_OVERFLOW)) std::cout << " FE_OVERFLOW raised\n"; }

Possible output: