std::map<T, bool>, count values that are true

Question

I have a map:

std::map<std::string, bool> all_triggers_didfire;

I fill it and in the end would like to obtain the number of values that are true. The following code works:

int count_did_fire = std::count_if(
  all_triggers_didfire.begin(), 
  all_triggers_didfire.end(), 
  [](std::pair<std::string, bool> p){return p.second;}
);

Is there an easier way than to define a lambda expression for this?

Answer 1

I would use std::set instead of std::map. They are semantically equivalent but using std::set is easier. Example:

std::set<std::string> triggers_that_did_fire;
int count_did_fire = triggers_that_did_fire.size();

When you originally populate the triggers_that_did_fire set, you can do the following:

triggers_that_did_fire.insert(mystring); //equivalent to setting to "true" in your map
triggers_that_did_fire.remove(mystring); //equivalent to setting to "false"

Answer 2

Sometimes, a simple for loop is a little clearer:

auto count = 0;
for (auto&& p : all_triggers_didfire)
  if (p.second)
    ++count;

EDIT 1: I'll post the original code in case anyone cannot see the edit history..

auto count = 0;
for (auto& p : all_triggers_didfire)
  count += p.second;