lower_bound() с лямбда-функцией

template <typename T>
pair<T, T> func(T range_begin, T range_end, char p)
{
    auto left = lower_bound(range_begin, range_end, p, [=](string s)
    {
         if (s[0] == p) ???
             ???
    });
 
}

auto left = lower_bound(range_begin, range_end, p, [](char ch1, char ch2)
    {
return ch1 < ch2;
    });

#include <iostream>
#include <algorithm>
#include <vector>
 
using namespace std;
 
template <typename T>
pair<T, T> func(T range_begin, T range_end, char p)
{
    auto left = lower_bound(range_begin, range_end, p, [=](string s)
    {   
    });
    auto right = upper_bound(range_begin, range_end, p, [=](string s)
    {   
    });
    
    return make_pair(left, right);
 
}
int main() {
  const vector<string> strings = {"aaa", "bbb", "ppp", "pppas", "yuaz"};
 
  const auto res =
      func(begin(strings), end(strings), 'p');
  for (auto it = res.first; it != res.second; ++it) {
    cout << *it << " ";
  }
  cout << endl;
 
}

template <typename T>
pair<T, T> func(T range_begin, T range_end, char p)
{
    auto left = lower_bound(range_begin, range_end, p, [](const string &s, char ch)
    {   
        return s[0] < ch;
    });
    auto right = upper_bound(left, range_end, p, [](char ch, const string &s)
    {   
        return ch < s[0];
    });
    
    return make_pair(left, right);
}