Bit operator
| operator | function | example |
|---|
| « | left shift | 0001 –> 0010 |
| » | right shift | 0010 –> 0001 |
| & | and (bit by bit) | 1100 & 1010 = 1000 |
| | | or (bit by bit) | 1010 | 0101 = 1111 |
| ~ | reverse | ~0000 = 1111 |
| ^ | XOR | 0110 ^ 1100 = 1010 |
Operator: &
x is a bit
x & 1 = x
x & 0 = 0
Usually use & as a filter. Suppose we have a number is X, X & 0011 will get the last two bits of X.
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| #include <iostream>
using namespace std;
int main(int argc, char const *argv[])
{
int testInt = 123;
cout << "The test integer is: " << testInt << endl;
cout << "The binary number is: " << endl;
for (int i = 31; i >= 0; --i)
{
int tmp = testInt & (1 << i);
if(tmp == 0)
cout << '0';
else
cout << '1';
if(i % 4 == 0)
cout << ' ';
}
cout << endl;
return 0;
}
|
Operator: |
Wave Adder. One is 1 result will be 1.
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| #include <iostream>
#include <bitset>
using namespace std;
int main(int argc, char const *argv[])
{
// we want a wave like 111000
int begin = 1 << 3; // 1000
for(int i = 0 ; i < 2; ++i){
begin = begin | begin << 1;
}
bitset<8> test(begin);
cout << test << endl;
cout << begin << endl;
}
|
Operator: ^
Canceller. Same is 0 otherwise is 1.
a ^ b = c —> b = c ^ a
bitset
Official Doc
bitset is stable structure that boolean value in only one bit. It need prefix the size.
The defect of bitset is that it cannot extend. vector<bool> don’t need to array about the size however that is defective at design level. Instead, we can use vector<char>. (char is 4 bits in c++)
bitset use for a huge mount of boolean data. Bitset need 8 bytes at beginning(64 bit memory). If the array of boolean data is small( <8 bytes), you better use a integer or long integer to store and use bit operator to manipulate. Definitely, bitset is more easy to use.
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| #include <iostream>
#include <bitset>
#include <string>
using namespace std;
int main(int argc, char const *argv[])
{
int val = 9;
bitset<4> foo(val); // 1001
bitset<4> bar("0011"); // 0011
bitset<4> baz(0xf); // 1111
cout << foo << endl;
cout << bar << endl;
cout << baz << endl;
cout << "calculation" << endl;
cout << (foo & bar) << endl; // 0001
cout << (foo | bar) << endl; // 1011
cout << (foo ^ bar) << endl; // 1010
cout << "foo = " << (foo |= bar) << endl; // foo = 1011
// foo = 1011
// foo[0] = 1; foo[2] = 1; foo[3] = 0; foo[4] = 1;
for (int i = 0; i < 4; ++i)
{
cout << foo[i] << ' ';
}
cout << endl;
}
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