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POCreating a function that is a friend to multiple classes
 

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  1. POCreating a function that is a friend to multiple classes
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    <p>In the code below, I am trying to create a function "patient_count" that is a friend to the classes "horse" , "pig" , and "dog". I can get the function to be a friend with 1 class but not to all 3. Can anyone tell me what my mistake is? </p> <pre><code>/*******************************************************\ * Veternarian Class Problem - I need a class for each * * of 3 animals. Horse, Pig and Dogs * \*******************************************************/ #include &lt;cstdlib&gt; #include &lt;iostream&gt; #include &lt;string&gt; const int HORSE_KENNEL = 100; // Number of horses we can store const int PIG_KENNEL = 100; // Number of Pigs we can store const int DOG_KENNEL = 100; // Number of Dogs we can store /*******************************************************\ * Class horse * * * * Member functions * * horse_count -- Keeps track of the number of horses * * add_horse -- Sends data into the object * * next_horse -- returns data from the object * \*******************************************************/ // Definition of the Class class horse { private: int horse_count; // Variable to keep track of data std::string horse_data[HORSE_KENNEL]; // A Place to put the data // Declarations for the method Prototypes public: // Initialize horse( ); // A Function that accepts an argument but returns nothing void add_horse(const std::string new_horse_data); // This method returns the next Horse in the queue std::string next_horse( ); friend int patient_count(horse); }; /*******************************************************\ * Method Definition - Here we flush out the prototypes * * outlined in the last section * \*******************************************************/ inline horse::horse( ) { for(int i = 0; i &lt; HORSE_KENNEL; ++i){ horse_data[i] = "Empty Spot"; } horse_count = 0; // Zero the data count } /*******************************************************\ * horse::add_horse -- Send data to Object * \*******************************************************/ inline void horse::add_horse(const std::string new_horse_data) { horse_data[horse_count] = new_horse_data; ++horse_count; } /*******************************************************\ * horse::next_horse - get data from object * \*******************************************************/ inline std::string horse::next_horse( ) { // this is specifically implementing a queue std::string current_horse = " "; int target_horse = 0; for(int i = 0;i &lt; HORSE_KENNEL; ++i){ if(horse_data[i] != "Empty Spot"){ std::cout &lt;&lt; "Horse Number " &lt;&lt; i &lt;&lt; " " &lt;&lt; horse_data[i] &lt;&lt; std::endl; } } std::cout &lt;&lt; "Select the horse you want: "; std::cin &gt;&gt; target_horse; return (horse_data[target_horse]); } /*******************************************************\ * Class Pig * * * * Member functions * * pig_count -- Keeps track of the number of pigs * * add_pig -- Sends data into the object * * next_pig -- returns data from the object * \*******************************************************/ // Definition of the Class class pig { private: int pig_count; // Variable to keep track of data std::string pig_data[PIG_KENNEL]; // A Place to put the data // Declarations for the method Prototypes public: // Initialize pig( ); // A Function that accepts an argument but returns nothing void add_pig(const std::string new_pig_data); // This method returns the next pig in the queue std::string next_pig( ); friend pig patient_count(pig); }; /*******************************************************\ * Method Definition - Here we flush out the prototypes * * outlined in the last section * \*******************************************************/ inline pig::pig( ) { for(int i = 0; i &lt; PIG_KENNEL; ++i){ pig_data[i] = "Empty Spot"; } pig_count = 0; // Zero the data count } /*******************************************************\ * pig::add_pig -- Send data to Object * \*******************************************************/ inline void pig::add_pig(const std::string new_pig_data) { pig_data[pig_count] = new_pig_data; ++pig_count; } /*******************************************************\ * pig::next_pig - get data from object * \*******************************************************/ inline std::string pig::next_pig( ) { // this is specifically implementing a queue std::string current_pig = " "; int target_pig = 0; for(int i = 0;i &lt; PIG_KENNEL; ++i){ if(pig_data[i] != "Empty Spot"){ std::cout &lt;&lt; "pig Number " &lt;&lt; i &lt;&lt; " " &lt;&lt; pig_data[i] &lt;&lt; std::endl; } } std::cout &lt;&lt; "Select the pig you want: "; std::cin &gt;&gt; target_pig; return (pig_data[target_pig]); } /*******************************************************\ * Class dog * * * * Member functions * * dog_count -- Keeps track of the number of dogs * * data_to_object -- Sends data into the object * * data_from_object -- returns data from the object * \*******************************************************/ // Definition of the Class class dog { private: int dog_count; // Variable to keep track of data std::string dog_data[DOG_KENNEL]; // A Place to put the data // Declarations for the method Prototypes public: // Initialize dog( ); // A Function that accepts an argument but returns nothing void add_dog(const std::string new_dog_data); // This method returns the next dog in the queue std::string next_dog( ); friend dog patient_count(dog); }; /*******************************************************\ * Method Definition - Here we flush out the prototypes * * outlined in the last section * \*******************************************************/ inline dog::dog( ) { for(int i = 0; i &lt; DOG_KENNEL; ++i){ dog_data[i] = "Empty Spot"; } dog_count = 0; // Zero the data count } /*******************************************************\ * dog::add_dog -- Send data to Object * \*******************************************************/ inline void dog::add_dog(const std::string new_dog_data) { dog_data[dog_count] = new_dog_data; ++dog_count; } /*******************************************************\ * dog::next_dog - get data from object * \*******************************************************/ inline std::string dog::next_dog( ) { // this is specifically implementing a queue std::string current_dog = " "; int target_dog = 0; for(int i = 0;i &lt; DOG_KENNEL; ++i){ if(dog_data[i] != "Empty Spot"){ std::cout &lt;&lt; "dog Number " &lt;&lt; i &lt;&lt; " " &lt;&lt; dog_data[i] &lt;&lt; std::endl; } } std::cout &lt;&lt; "Select the dog you want: "; std::cin &gt;&gt; target_dog; return (dog_data[target_dog]); } /**************************************************\ * This function is a friend of all the animal * * classes and returns the total of all animals * * PROBLEM ******* PROBLEM *********PROBLEM ********* * When I add the other 2 classes on the next line * * The program stops working * \**************************************************/ // int patient_count(horse target_horse) //works int patient_count(horse target_horse, pig target_pig, dog target_dog) // Nova { // int all_animals = target_horse.horse_count; //Works int all_animals = target_horse.horse_count + target_pig.pig_count + target_dog.dog_count; // Nova return (all_animals); } /**************************************************\ * The Class is defined above, this section is a * * Small testing harness to verify that the class * * is doing what it was designed to do * \**************************************************/ int main( ) { int total_animals; horse current_horse; // Create a instance // Send 3 values to the object current_horse.add_horse("Mr Ed, 10, Male"); current_horse.add_horse("Lightning, 4, Female"); current_horse.add_horse("Blitz, 7, Male"); // Call for the return of the 3 values std::cout &lt;&lt; "Selected Horse -&gt;" &lt;&lt; current_horse.next_horse( ) &lt;&lt; '\n'; pig current_pig; // Create a instance // Send 3 values to the object current_pig.add_pig("Arnold, 4, Male"); current_pig.add_pig("Babe, 2, Female"); current_pig.add_pig("Killer, 7, Male"); // Call for the return of the 3 values std::cout &lt;&lt; "Selected Pig -&gt;" &lt;&lt; current_pig.next_pig( ) &lt;&lt; '\n'; dog current_dog; // Create a instance // Send 3 values to the object current_dog.add_dog("Misty, 15, Female"); current_dog.add_dog("Tristian, 12, Male"); current_dog.add_dog("Tempest, 11, Female"); // Call for the return of the 3 values std::cout &lt;&lt; "Selected Dog -&gt;" &lt;&lt; current_dog.next_dog( ) &lt;&lt; '\n'; // Now get the results from the friend function // total_animals = patient_count(current_horse); // Works total_animals = patient_count(current_horse, current_pig, current_dog); // Nova std::cout &lt;&lt; "Total Animals: " &lt;&lt; total_animals &lt;&lt; std::endl; return (0); } </code></pre>
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    1. USNicole Cook
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    1. COWay to write a **minimal example**! I think your function signatures don't match in your `friend` declarations.
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      1. USKerrek SB
    2. CO@Kerrek: was that sarcasm, irony, or praise?
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    3. CO@Sehe: An effort to make future questions more palatable while at once having some fun :-)
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      1. USKerrek SB
 

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