class - Conversion constructor between classes c++ -

the background: reading wonderful book, briefly mentioned conversion constructors.

though understand fundamentals of conversion constructors, bit lost, when in practice problems section asked:

write conversion constractor converts ratnum realnum code received prior problem:

class ratnum {     int num, denom; public:     ratnum(int numenator = 2, int denominator = 3) : num(numenator), denom(denominator) {}     void show() { cout << static_cast<double>(num) / denom << endl; }     double result() { return num / denom; }  };  class realnum {     int number; public:     realnum(double numr = 0) : number (numr) {} };   

i dealt conversion constructors such:

ratnum 1 = 10; //or ratnum 2 = {10, 2} 

but never saw can convert class class type. you, please, how such conversion constructor should work (maybe example)?

is defining function result of ratnum class , writing:

realnum check = one.result(); 

is meant here?

i assume meant there overload of constructor takes input of other class, example

realnum(ratnum const& other) : number{other.result()} {} 

and vice-versa construct ratnum realnum, although less trivial there irrational numbers, infinitely repeating numbers, etc.

you use version of constructor like

ratnum a{2, 4}; realnum b{a};    // used "conversion" constructor