vector<bool> and groupby

[miguel-negrao]

Hi

I'm getting another strange behaviour:

  vector<bool> v{true, true, false, false,false, true, true};
  for (auto &&x: iter::groupby(v,[](auto b){return b;})) {
    cout << "group: ";
    for (auto &&g: x.second)
      cout << g << " ";
    cout << endl;
  }

prints

group: 1 1 0 0 0 1 1 

yet

  vector<int> v{5,5,5,3,3};
  for (auto &&x: iter::groupby(v,[](auto b){return b;})) {
    cout << "group: ";
    for (auto &&g: x.second)
      cout << g << " ";
    cout << endl;
  }

prints

group: 5 5 5 
group: 3 3

Is there a reason why it shouldn't work with bool ?

[ryanhaining]

This is definitely a more insidious bug surely related to std::vector being a specialization. It should work with bool. Looking into it

[ryanhaining]

Still trying to figure out exactly what is going on here, but it looks to be related to std::vector<bool>::operator*'s proxy object. If you change your lambda to take bool instead of auto the code works as expected.

It doesn't work, however with the default identity functionality of groupby(v), so I've got an issue there too.