c++, logical operators

Question

Write a tiny library and submit it in files AboutDog.h and AboutDog.cpp. This library has the only function:

void AboutDog(const std::string & dogName, unsigned int description)

The function AboutDog outputs on the screen the following text:

This dog is called *dogName*. It is *list of dog features from description*.

description encodes the dogs properties the following way:

1.  set bit 0 means the dog is big
2.  set bit 1 means the dog is hairy
3.  set bit 2 means the dog is brown
4.  set bit 3 means the dog is smart

In the header file, define MACROS: DOG_BIG, DOG_HAIRY, DOG_BROWN, DOG_SMART.

I should be able to call the function like this:

AboutDog( "Spike", DOG_BROWN | DOG_SMART | DOG_HAIRY );

The above call should produce the output like this:

This dog is called Spike. It is hairy brown smart.

The order of features doesn't matter. Punctuation doesn't matter too. If description==0 skip the second sentence.

/****************************

Does anything else go into AboutDog.h?

#define DOG_BIG (0x1)

#define DOG_HAIRY (0x2)

#define DOG_BROWN (0x4)

#define DOG_SMART (0x8)

In AboutDog.cpp, how to output dog features?

Answer 1

In AboutDog.h you have defined the descriptions which is fine, but I would also declare the AboutDog function. By having the function declaration in the header, any other source file could just include the header and call the function. Here is what the header would look like:

------------------------------------------------------------------------------

// AboutDog.h

#include <string>

#define DOG_BIG (0x1)

#define DOG_HAIRY (0x2)

#define DOG_BROWN (0x4)

#define DOG_SMART (0x8)

void AboutDog(const std::string &dogName, unsigned int description);

------------------------------------------------------------------------------

In the AboutDog.cpp file, you can add the function definition. Here is an example:

------------------------------------------------------------------------------

// AboutDog.cpp

#include <iostream>

#include "AboutDog.h"

// I intentionally do not add the using namespace for the

// std library in the cpp or header. This is a practice that

// is discouraged in any larger project since it can cause

// naming conflicts, compiler errors when using differnet

// headers and libraries together with the std libraries.

// It is a good habit to get used to using the fully

// qualified names of the functions.

// using namespace std;

void AboutDog(const std::string &dogName, unsigned int description)

{

std::cout << "This dog is called ";

// Output the name if the given name is not empty

// and if the given name is empty, output the name

// UNKNOWN.

if(!dogName.empty())

{

std::cout << dogName << ".";

}

else

{

std::cout << "UNKNOWN.";

}

if(description != 0)

{

std::cout << " It is ";

// Use the binary AND operator to and the

// description with one of the defines.

// If the description contains a 1 in any

// of the bit positions defined, the result

// of the operation will be non-zero.

if(description & DOG_BIG)

{

std::cout << "big ";

}

if(description & DOG_HAIRY)

{

std::cout << "hairy ";

}

if(description & DOG_BROWN)

{

std::cout << "brown ";

}

if(description & DOG_SMART)

{

std::cout << "smart";

}

}

}

------------------------------------------------------------------------------

You can now include the header in your main.cpp and call it like any other function:

------------------------------------------------------------------------------

// main.cpp

#include "AboutDog.h"

int main()

{

AboutDog("Spike", DOG_BROWN | DOG_SMART | DOG_HAIRY);

return 0;

}

------------------------------------------------------------------------------

The output of the above code should be exactly as expected:

------------------------------------------------------------------------------

This dog is called Spike. It is hairy brown smart

------------------------------------------------------------------------------

Answer 2

#include <iostream>

#include <math.h>

#define DOG_BIG 1 //bit zero ---> 2^0=1

#define DOG_HAIRY 2 //bit one ---> 2^1 = 2

#define DOG_BROWN 4 //bit two ---> 2^2=4

#define DOG_SMART 8 // bit three --> 2^3=8

//#include "AboutDog.h"

using namespace std;

void AboutDog(const std::string & dogName, unsigned int description)

{

cout<<"This dog is called "<<dogName<<". ";

if (description != 0)

{

cout<<"It is";

if(description & DOG_BIG)

{

cout<<" big ";

}

if(description & DOG_HAIRY)

{

cout<<" hairy ";

}

if(description & DOG_BROWN)

{

cout<<" brown ";

}

if(description & DOG_SMART)

{

cout<<" smart ";

}

cout<<"."<<endl;

}

}

main()

{

AboutDog("Shotzy",DOG_BIG|DOG_SMART);