Bsrgvty

Most likely this is a XY problem. But ... just don't call it twice.

#include <iostream>

class Creature

public:
 virtual void identify()
 
 std::cout << "I'm a creature" << std::endl;
 
;

class Swimmer : public virtual Creature

public:
 virtual void identify() override
 
 Creature::identify();
 tell_ability();
 std::cout << "I'm a swimmern";
 

 virtual void tell_ability()
 
 std::cout << "I can swimn";
 
;

class Flier : public virtual Creature

public:
 virtual void identify() override
 
 Creature::identify();
 tell_ability();
 std::cout << "I'm a fliern";
 

 virtual void tell_ability()
 
 std::cout << "I can flyn";
 
;

class Duck : public Flier, public Swimmer

public:
 virtual void tell_ability() override
 
 Flier::tell_ability();
 Swimmer::tell_ability();
 

 virtual void identify() override
 
 Creature::identify();
 tell_ability();
 std::cout << "I'm a duckn";
 
;

int main()

 Creature c;
 c.identify();
 std::cout << "------------------n";

 Swimmer s;
 s.identify();
 std::cout << "------------------n";

 Flier f;
 f.identify();
 std::cout << "------------------n";

 Duck d;
 d.identify();
 std::cout << "------------------n";

Output:

I'm a creature
------------------
I'm a creature
I can swim
I'm a swimmer
------------------
I'm a creature
I can fly
I'm a flier
------------------
I'm a creature
I can fly
I can swim
I'm a duck
------------------

We can let the base class keep track of the attributes:

#include <iostream>
#include <string>
#include <vector>

using namespace std::string_literals;

class Creature

public:
 std::string const attribute"I'm a creature"s;
 std::vector<std::string> attributesattribute;
 virtual void print()
 
 for (auto& i : attributes)
 std::cout << i << std::endl;
 
;

class Swimmer : public virtual Creature

public:
 Swimmer() attributes.push_back(attribute); 
 std::string const attribute"I can swim"s;
;

class Flier : public virtual Creature

public:
 Flier() attributes.push_back(attribute); 
 std::string const attribute"I can fly"s;
;

class Duck : public Flier, public Swimmer

public:
 Duck() attributes.push_back(attribute); 
 std::string const attribute"I'm a duck"s;
;

int main()

 Duck d;
 d.print();

Likewise, if it is not just printing we're after, but rather the function calls, then we could let the base class keep track of the functions:

#include <iostream>
#include <functional>
#include <vector>

class Creature

public:
 std::vector<std::function<void()>> print_functions[this] Creature::print_this(); ;
 virtual void print_this()
 
 std::cout << "I'm a creature" << std::endl;
 
 void print()
 
 for (auto& f : print_functions)
 f();
 
;

class Swimmer : public virtual Creature

public:
 Swimmer() print_functions.push_back([this] Swimmer::print_this(); ); 
 void print_this()
 
 std::cout << "I can swim" << std::endl;
 
;

class Flier : public virtual Creature

public:
 Flier() print_functions.push_back([this] Flier::print_this(); ); 
 void print_this()
 
 std::cout << "I can fly" << std::endl;
 
;

class Duck : public Flier, public Swimmer

public:
 Duck() print_functions.push_back([this] Duck::print_this(); ); 
 void print_this()
 
 std::cout << "I'm a duck" << std::endl;
 
;

int main()

 Duck d;
 d.print();

An easy way is to create a bunch of helper classes that mimick the inheritance structure of your main hierarchy and do all the printing in their constructors.

 struct CreaturePrinter 
 CreaturePrinter() 
 std::cout << "I'm a creaturen";
 
 ;

 struct FlierPrinter: virtual CreaturePrinter ... 
 struct SwimmerPrinter: virtual CreaturePrinter ...
 struct DuckPrinter: FlierPrinter, SwimmerPrinter ...

Then each print method in the main hierarchy just creates the corresponding helper class. No manual chaining.

For maintainability you can make each printer class nested in its corresponding main class.

Naturally in most real world cases you want to pass a reference to the main object as an argument to the constructor of its helper.

Your explicit calls to the print methods form the crux of the issue.

One way round this would be to drop the print calls, and replace them with say

void queue(std::set<std::string>& data)

and you accumulate the print messages into the set. Then it doesn't matter those functions in the hierarchy get called more than once.

You then implement the printing of the set in a single method in Creature.

If you want to preserve the order of printing, then you'd need to replace the set with another container that respects the order of insertion and rejects duplicates.

If you want that middle class method, do not call the base class method. The easiest and simplest way is to extract extra methods, and then reimplementing Print is easy.

class Creature

 public:
 virtual void print()
 
 std::cout << "I'm a creature" << std::endl;
 
;

class Swimmer : public virtual Creature

 public:
 void print()
 
 Creature::print();
 detailPrint();
 

 void detailPrint()
 
 std::cout << "I can swim" << std::endl;
 
;

class Flier : public virtual Creature

 public:
 void print()
 
 Creature::print();
 detailPrint();
 

 void detailPrint()
 
 std::cout << "I can fly" << std::endl;
 
;

class Duck : public Flier, public Swimmer

 public:
 void print()
 
 Creature::Print();
 Flier::detailPrint();
 Swimmer::detailPrint();
 detailPrint();
 

 void detailPrint()
 
 std::cout << "I'm a duck" << std::endl;
 
;

Without details what is your actual problem is, it hard to come up with a better solution.

Use:

template<typename Base, typename Derived>
bool is_dominant_descendant(Derived * x) 
 return std::abs(
 std::distance(
 static_cast<char*>(static_cast<void*>(x)),
 static_cast<char*>(static_cast<void*>(dynamic_cast<Base*>(x)))
 )
 ) <= sizeof(Derived);
;

class Creature

public:
 virtual void print()
 
 std::cout << "I'm a creature" << std::endl;
 
;

class Walker : public virtual Creature

public:
 void print()
 
 if (is_dominant_descendant<Creature>(this))
 Creature::print();
 std::cout << "I can walk" << std::endl;
 
;

class Swimmer : public virtual Creature

public:
 void print()
 
 if (is_dominant_descendant<Creature>(this))
 Creature::print();
 std::cout << "I can swim" << std::endl;
 
;

class Flier : public virtual Creature

public:
 void print()
 
 if (is_dominant_descendant<Creature>(this))
 Creature::print();
 std::cout << "I can fly" << std::endl;
 
;

class Duck : public Flier, public Swimmer, public Walker

public:
 void print()
 
 Walker::print();
 Swimmer::print();
 Flier::print();
 std::cout << "I'm a duck" << std::endl;
 
;

And with Visual Studio 2015 the output is:

I'm a creature
I can walk
I can swim
I can fly
I'm a duck

But is_dominant_descendant does not have a portable definition. I wish it were a standard concept.