text: #ifndef POLYMER_H_
  #define POLYMER_H_
  
  #include "pair.h"
  #include "parsing.h"
  #include <string>
  #include <unordered_map>
  #include <vector>
  
  struct FrequencyCounter {
    FrequencyCounter(const std::string &);
    void tick(const InsertionRules &);
    std::vector<uint64_t> char_freq;
    std::unordered_map<Pair, uint64_t> pair_freq;
  };
  
  #endif