Initialize inline vector of bool

Question

I am using this example to initialize the bool vector:

#include <iostream>
#include <map>
#include <vector>
using namespace std;

int main() {
 map<int, vector<bool> > myMap;
 vector<bool> one {true, true, false};
 myMap[2] = one;
 cout << myMap[2][0] << endl;
 cout << myMap[2][1] << endl;
 cout << myMap[2][2] << endl;
 return 0;
}

The only change I made in this code is using std::vector instead of vector and I now have:

std::map<int, std::vector<bool> >  m_links;
std::vector<bool> m_allFalse {false, false, false, false, false};

It tells me to use ; after m_allFalse. How can I get rid of this error?

I am using intel compiler 14, but without c++11.

Answer 1

Problem is:

std::vector<bool> m_allFalse {false, false, false, false, false};

wrong syntax in standard C++. (maybe in C++11, I don't know)

You can use this instance:

std::vector<bool> m_allFalse(5, false); (*)

If you want C++11 edit your tag and follow @lakesh tip.

(*) this constructor is explained in vector documentation:

(2) fill constructor Constructs a container with n elements. Each element is a copy of val.

To initialize general boolean values at the beginning, you can use this way:

bool tempBool[] = { true, false, false, true };
std::vector<bool> variousBool ( tempBool, tempBool + sizeof(tempBool) / sizeof(bool) );

Knowing this, you could create your own vector class, simply inheriting from vector (if you want you can use template to extend to all types):

class PimpedVector : public std::vector<bool>  {
public:
  PimpedVector(const unsigned int& size, ...) {
    va_list args;
    va_start(args, size); 
    for ( size_t i = 0; i < size; ++i ) {
      bool b = va_arg(args, bool);
      this->push_back(b);
    }
  }
}

So from your main you can create a PimpedVector in this way:

PimpedVector p0(5, true, false, false, true, false);

Answer 2

The feature you're using was introduced in C++11. Since, as your question edit reveals, you're compiling as C++98, the compiler rightfully complains about it, because it is not valid C++98 syntax.

For the special case of all values being the same, the C++98 way (still working in C++11, and for this special case preferred there, too) to initialize is, as mentioned by Velthune,

std::vector<bool> m_allFalse(5, false);

Actually since std::vector default-initializes all its values, and false is the default value of bool, for that specific case you can even simplify it to

std::vector<bool> m_allFalse(5);

If you want more general values, you'll have to copy them in, for example:

std::vector<bool> foo(3);
foo[0] = foo[1] = true;
foo[2] = false; // that line is actually not needed because of default initialization of members

or

std::vector<bool> foo;
foo.push_back(true);
foo.push_back(true);
foo.push_back(false); // this time, it is needed because it actually created the thirs argument

An additional note: I notice the m_ prefix of your variable name; this suggests that you're declaring a member variable (if so, that's a crucial detail which you left out). A member variable cannot (in C++98) be given an initializer (of any sort) at its declaration (with the exception of static const members of integer type). For non-static member variables, you have to initialize them at the constructor call, for example:

class X
{
public:
  X(); // the constructor
private:
  std::vector<bool> m_Foo;
};

// constructor definition follows
X::X():
  m_Foo(5, false) // this initializes your member variable `m_Foo`
{
}