Class containing a vector: writing the at method

Asked Oct 16 '17 at 15:18

Active Oct 16 '17 at 15:18

Viewed 28 times

#include <vector>
using namespace std;

class State {
private:
  vector<bool> probabilities;
public:
  State(int size) {
    probabilities = vector<bool>(size,false);
  };
  bool &at(int i) { return probabilities.at(i); };
};

I see a couple of questions about classes that contain a vector. However, I do not see the point addressed of how to write an "at" method that takes the "at" of the included vector.

The above code gives:

state.cxx: In member function 'bool& State::at(int)':                                             
state.cxx:11:44: error: cannot bind non-const lvalue reference of type 'bool&' to an rvalue of type 'bool'                                                                                           
   bool &at(int i) { return probabilities.at(i); };

So I'm clearly missing something about how references work.

asked Oct 16 '17 at 15:18

Victor Eijkhout

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a `vector` isnt really a `vector` of `bool`s – 463035818_is_not_an_ai Oct 16 '17 at 15:21
https://stackoverflow.com/questions/8399417/why-vectorboolreference-doesnt-return-reference-to-bool – Artemy Vysotsky Oct 16 '17 at 15:21
a simple workaround is to use a `vector` with `struct my_bool { bool value; }` looks stupid, but thats how it is, `std::vector` was a mistake – 463035818_is_not_an_ai Oct 16 '17 at 15:23
Thanks guys. I hadn't found the other question. Will study. – Victor Eijkhout Oct 16 '17 at 15:24

Class containing a vector: writing the at method

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