Convert vector<bool> to binary - c++

Question

I have a vector<bool> that contains 10 elements. How can I convert it to a binary type;
vector<bool> a={0,1,1,1,1,0,1,1,1,0}
I want to get binary values, something like this:
long long int x = convert2bin(s)
cout << "x = " << x << endl
x = 0b0111101110
Note: the size of vector will be change during run time, max size = 400.
0b is important, I want to use the gcc extension, or some literal type.

Answer 1

As I understood of comment
Yes it can even hold 400 values
And in question
0b is important
You need to have string, not int.
std::string convert2bin(const std::vector<bool>& v)
{
std::string out("0b");
out.reserve(v.size() + 2);
for (bool b : v)
{
out += b ? '1' : '0';
}
return i;
}

Answer 2

std::vector<bool> a = { 0, 1, 1, 1, 1, 0, 1, 1, 1, 0 };
std::string s = "";
for (bool b : a)
{
s += std::to_string(b);
}
int result = std::stoi(s);

Answer 3

If you really want to do this, you start from the end. Although I support Marius Bancila and advise to use a bitset instead.
int mValue = 0
for(int i=a.size()-1, pos=0; i>=0; i--, pos++)
{
// Here we create the bitmask for this value
if(a[i] == 1)
{
mask = 1;
mask << pos;
myValue |= mask;
}
}

Answer 4

Your x is just an integer form from a, so can use std::accumulate like following
long long x = accumulate(a.begin(), a.end(), 0,
[](long long p, long long q)
{ return (p << 1) + q; }
);
For a 400 size, you need a std::string though

Answer 5

First of all the result of the conversion is not a literal. So you may not use prefix 0b applied to variable x.
Here is an example
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <numeric>
#include <vector>
#include <iterator>
#include <limits>
int main()
{
std::vector<bool> v = { 0, 1, 1, 1, 1, 0, 1, 1, 1, 0 };
typedef std::vector<bool>::size_type size_type;
size_type n = std::min<size_type>( v.size(),
std::numeric_limits<long long>::digits + 1 );
long long x = std::accumulate( v.begin(), std::next( v.begin(), n ), 0ll,
[]( long long acc, int value )
{
return acc << 1 | value;
} );
for ( int i : v ) std::cout << i;
std::cout << std::endl;
std::cout << std::hex << x << std::endl;
return 0;
}
The output is
0111101110
1ee

Answer 6

vector<bool> is already a "binary" type.
Converting to an int is not possible for more bits than available in an int. However if you want to be able to print in that format, you can use a facet and attach it to the locale then imbue() before you print your vector<bool>. Ideally you will "store" the locale once.
I don't know the GNU extension for printing an int with 0b prefix but you can get your print facet to do that.
A simpler way is to create a "wrapper" for your vector<bool> and print that.
Although vector<bool> is always internally implemented as a "bitset" there is no public method to extract the raw data out nor necessarily a standard representation for it.
You can of course convert it to a different type by iterating through it, although I guess you may have been looking for something else?

Answer 7

If the number of bits is known in advance and by some reason you need to start from an std::array rather than from an std::bitset directly, consider this option (inspired by this book):
#include <sstream>
#include <iostream>
#include <bitset>
#include <array>
#include <iterator>
/**
* #brief Converts an array of bools to a bitset
* #tparam nBits the size of the array
* #param bits the array of bools
* #return a bitset with size nBits
* #see https://www.linuxtopia.org/online_books/programming_books/c++_practical_programming/c++_practical_programming_192.html
*/
template <size_t nBits>
std::bitset<nBits> BitsToBitset(const std::array<bool, nBits> bits)
{
std::ostringstream oss;
std::copy(std::begin(bits), std::end(bits), std::ostream_iterator<bool>(oss, ""));
return std::bitset<nBits>(oss.str());
}
int main()
{
std::array<bool, 10> a = { 0, 1, 1, 1, 1, 0, 1, 1, 1, 0 };
unsigned long int x = BitsToBitset(a).to_ulong();
std::cout << x << std::endl;
return x;
}