std::exp2, std::exp2f, std::exp2l
From cppreference.com
Defined in header <cmath>
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(1) | ||
float exp2 ( float num ); double exp2 ( double num ); |
(until C++23) | |
/* floating-point-type */ exp2 ( /* floating-point-type */ num ); |
(since C++23) (constexpr since C++26) |
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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) |
Additional overloads (since C++11) |
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Defined in header <cmath>
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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.
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(since C++11) |
Contents |
[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
Run this code
#include <cerrno> #include <cfenv> #include <cmath> #include <cstring> #include <iostream> // #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:
exp2(4) = 16 exp2(0.5) = 1.41421 exp2(-4) = 0.0625 exp2(-0) = 1 exp2(-Inf) = 0 exp2(1024) = inf errno == ERANGE: Numerical result out of range FE_OVERFLOW raised
[edit] See also
(C++11)(C++11) |
returns e raised to the given power (ex) (function) |
(C++11)(C++11)(C++11) |
returns e raised to the given power, minus one (ex-1) (function) |
(C++11)(C++11) |
multiplies a number by 2 raised to an integral power (function) |
(C++11)(C++11)(C++11) |
base 2 logarithm of the given number (log2(x)) (function) |
C documentation for exp2
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