Difference between revisions of "cpp/numeric/rotr"
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| − | Computes the result of bitwise right-rotating the value of {{c|x}} by {{c|s}} positions. This operation is also known as a right | + | Computes the result of bitwise right-rotating the value of {{c|x}} by {{c|s}} positions. This operation is also known as a right {{enwiki|Circular shift|circular shift}}. |
| − | Formally, let {{tt|N}} be {{c|std::numeric_limits<T>::digits}} | + | Formally, let {{tt|N}} be {{c/core|std::numeric_limits<T>::digits}} and {{c|r}} be {{c|s % N}}. |
| − | * If {{ | + | * If {{c|r}} is {{c|0}}, returns {{c|x}}; |
| − | * if {{ | + | * if {{c|r}} is positive, returns {{c|(x >> r) {{!}} (x << (N - r))}}; |
| − | * if {{ | + | * if {{c|r}} is negative, returns {{c|std::rotl(x, -r)}}. |
| − | {{cpp/enable_if|{{tt|T}} is an unsigned integer type (that is, {{c|unsigned char}}, {{c|unsigned short}}, {{c|unsigned int}}, {{c|unsigned long}}, {{c|unsigned long long}}, or an extended unsigned integer type)}}. | + | {{cpp/enable_if|{{tt|T}} is an unsigned integer type (that is, {{c/core|unsigned char}}, {{c/core|unsigned short}}, {{c/core|unsigned int}}, {{c/core|unsigned long}}, {{c/core|unsigned long long}}, or an extended unsigned integer type)}}. |
===Parameters=== | ===Parameters=== | ||
| Line 25: | Line 25: | ||
===Notes=== | ===Notes=== | ||
| − | {{feature test macro|__cpp_lib_bitops|std=C++20|value=201907L|[[cpp/numeric# | + | {{feature test macro|__cpp_lib_bitops|std=C++20|value=201907L|[[cpp/numeric#Bit manipulation (since C++20)|Bit operations]]}} |
| − | === Example === | + | ===Example=== |
{{example | {{example | ||
|code= | |code= | ||
| Line 37: | Line 37: | ||
int main() | int main() | ||
{ | { | ||
| − | + | using bin = std::bitset<8>; | |
| − | std:: | + | const std::uint8_t x{0b00011101}; |
| − | std::cout << | + | std::cout << bin(x) << " <- x\n"; |
| − | + | for (const int s : {0, 1, 9, -1, 2}) | |
| − | + | std::cout << bin(std::rotr(x, s)) << " <- rotr(x, " << s << ")\n"; | |
| − | + | ||
} | } | ||
|output= | |output= | ||
| − | + | 00011101 <- x | |
| − | rotr( | + | 00011101 <- rotr(x, 0) |
| − | rotr( | + | 10001110 <- rotr(x, 1) |
| − | rotr( | + | 10001110 <- rotr(x, 9) |
| − | rotr( | + | 00111010 <- rotr(x, -1) |
| + | 01000111 <- rotr(x, 2) | ||
}} | }} | ||
| − | === See also === | + | ===See also=== |
{{dsc begin}} | {{dsc begin}} | ||
{{dsc inc|cpp/numeric/dsc rotl}} | {{dsc inc|cpp/numeric/dsc rotl}} | ||
Latest revision as of 13:22, 2 November 2024
| Defined in header <bit>
|
||
| template< class T > constexpr T rotr( T x, int s ) noexcept; |
(since C++20) | |
Computes the result of bitwise right-rotating the value of x by s positions. This operation is also known as a right circular shift.
Formally, let N be std::numeric_limits<T>::digits and r be s % N.
- If r is 0, returns x;
- if r is positive, returns (x >> r) | (x << (N - r));
- if r is negative, returns std::rotl(x, -r).
This overload participates in overload resolution only if T is an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type).
Contents |
[edit] Parameters
| x | - | value of unsigned integer type |
| s | - | number of positions to shift |
[edit] Return value
The result of bitwise right-rotating x by s positions.
[edit] Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_bitops |
201907L | (C++20) | Bit operations |
[edit] Example
Run this code
#include <bit> #include <bitset> #include <cstdint> #include <iostream> int main() { using bin = std::bitset<8>; const std::uint8_t x{0b00011101}; std::cout << bin(x) << " <- x\n"; for (const int s : {0, 1, 9, -1, 2}) std::cout << bin(std::rotr(x, s)) << " <- rotr(x, " << s << ")\n"; }
Output:
00011101 <- x 00011101 <- rotr(x, 0) 10001110 <- rotr(x, 1) 10001110 <- rotr(x, 9) 00111010 <- rotr(x, -1) 01000111 <- rotr(x, 2)
[edit] See also
| (C++20) |
computes the result of bitwise left-rotation (function template) |
| performs binary shift left and shift right (public member function of std::bitset<N>)
|
