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Why doesn't following program compile ?

Posted on 2013-10-31
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Last Modified: 2013-10-31
#include <iostream>
#include <string>


class GradeBook
{
public:
   GradeBook( string ); 
   void setCourseName( string ); 
   string getCourseName(); 
   void displayMessage();    
   
private:
   string courseName; 
};


int main()
{

  GradeBook gradebook1, another;
  
  GradeBook * ptr = &gradebook1;
  another = *ptr;

  if (gradebook1 == another)
  {
     std::cout << "They are equal\n";
  }
  return 0;
}

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The first error is as follows:  
test.cpp:8:22:  error:  field 'string' has incomplete type
        GradeBook( string );
0
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Question by:naseeam
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6 Comments
 
LVL 86

Accepted Solution

by:
jkr earned 1400 total points
ID: 39615213
Three issues with that code:

-  you forgot to use 'using namespace std:'
- you are missing a default constructor for 'GradeBook'
- the class is also missing a comarison operator

The following works, see the lines marked witn '// <---':

#include <iostream>
#include <string>
using namespace std; // <---

class GradeBook
{
public:
   GradeBook( string ); 
   GradeBook() {}; // <---
   void setCourseName( string ); 
   string getCourseName(); 
   void displayMessage(); 

   bool operator==(const GradeBook& r) const { return courseName == r.courseName;} // <---
   
private:
   string courseName; 
};


int main()
{

  GradeBook gradebook1, another;
  
  GradeBook * ptr = &gradebook1;
  another = *ptr;

  if (gradebook1 == another)
  {
     std::cout << "They are equal\n";
  }
  return 0;
}
                                  

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0
 
LVL 32

Assisted Solution

by:phoffric
phoffric earned 200 total points
ID: 39615214
See if std::string helps.
0
 
LVL 1

Author Comment

by:naseeam
ID: 39615237
= =   doesn't work for comparing variables that are type class ?  It must be overloaded ?
0
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LVL 1

Author Comment

by:naseeam
ID: 39615247
std::string works
0
 
LVL 86

Expert Comment

by:jkr
ID: 39615263
>>= =   doesn't work for comparing variables that are type class ?  It must be overloaded ?

Yes, there is no way to do that for complex types without an overload. Compilers can't be that smart ;o)

Oh, and prefixing 'string' with 'std' is not necessary if you refer to the namespace as above.
0
 
LVL 1

Author Closing Comment

by:naseeam
ID: 39615356
Thank you!
0

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