c++ - Common algorithm for maps with different comparison functions -


i have common algorithm 2 maps uses find() , operator[] access map. however, elsewhere in code need iterate on these maps , 1 of them needs sorted reverse comparison other. ended using reverse iterator map, profiling shows me huge amount of time wasted on dereferencing reverse iterator. tried following, didn't work:

struct custom {     list<double> doubles;     int integer = 0; };  typedef map<double, custom> custommap; typedef map<double, custom, std::greater<double>> custommapgreater;  custommap a; custommapgreater b;  ...  void algorithm(bool achosen) {     custommap* chosenmap;      if (achosen)     {         chosenmap = &a;     }     else     {         chosenmap = &b;    // conversion not possible     }      // algorithm uses chosenmap follows     ... }

any ideas on how can work? have feeling can done templates, i'm not proficient generic programming.

the template way like:

template <typename map> void algorithm(map& map) {     // ... }

or, in specific case, even

template <typename comp> void algorithm(std::map<double, custom, comp>& map) {     // ... }

and then

void algorithmchooser(bool achosen) {     if (achosen) {         algorithm(a);     } else {         algorithm(b);     } }

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