c++ left/right shift operator summary

c++ left/right shift operator summary

Logical shift and arithmetic shift

• Clarify two concepts (logical shift and arithmetic shift)
• There is a difference between logical shift and arithmetic shift, which is only for the left/right shift operations of signed integers. For unsigned integers, there is no difference between the two operations.

Unsigned integer

• Use logical shift, fill with "0" regardless of left shift and right shift

Signed integer

• Logical shift is the left shift operation of signed integer, the high bit is discarded, and the low bit is filled with "0"
• Arithmetic shift is the right shift operation of signed integer, the low bit is rounded off, and the high bit is filled with "sign bit"

constant

• For a constant, as long as the left shift exceeds 31 bits, it is 0

#include <bits/stdc++.h>
using namespace std;

template<class T>
void printf_2(T& x) {
    
    
	cout << x << "的二进制:" << bitset<1 * 8>(x) << endl; // sizeof(x)
}

int main() {
    
    
	unsigned short a = 0110;
	int b = 0110;
	int c = -0110;
	printf_2(a);
	a = a << 4; // 左移 逻辑移位
	printf_2(a);

	printf_2(b);
	printf_2(c);
	c = c >> 3; // 右移 算术移位

	// 算术移位，空出的部分用符号位填补
	// 逻辑移位 则用0填补

	printf_2(c);
	//cout << bitset<sizeof(b)>  << endl;
}