Declaring Class Instances

[me001]

hello!! i am writing a program about classes and i have a few problems. my program so far looks like this:

#include <iostream>
#include <fstream>
#include <iomanip>
 
using namespace std;
 
class Student
{
      private:
              char lastname[40];
              char firstname[40];
              char id[10];
              double gpa;
              int score;
              Student(char [], char [], char [], double , int);
              void showStudent();
              void setName(char [], char []);
              void setID(char []);
              int  setGPA(double );
              int  setScore(int );
              char getDecision();
 
};
 
int main()
{
 
     Person1 = ( " Stanko", " Bree", " Z146926", " 3.3", " 1598");
     Person2 = ( " Hartnett", " Josh", " Z123654", " -2.8", " 156");
 
     showStudent();
// ...
     return 0;
} 
 

in the int main, none of the functions or the person1/2 are declard. i have tried every way to d it and have looked at a 10 examples on google but it still will not compile. i am also confused with set functions. how can i chnage the name of someone??

[ilikepython]

hello!! i am writing a program about classes and i have a few problems. my program so far looks like this:

#include <iostream>
#include <fstream>
#include <iomanip>
 
using namespace std;
 
class Student
{
      private:
              char lastname[40];
              char firstname[40];
              char id[10];
              double gpa;
              int score;
              Student(char [], char [], char [], double , int);
              void showStudent();
              void setName(char [], char []);
              void setID(char []);
              int  setGPA(double );
              int  setScore(int );
              char getDecision();
 
};
 
int main()
{
 
     Person1 = ( " Stanko", " Bree", " Z146926", " 3.3", " 1598");
     Person2 = ( " Hartnett", " Josh", " Z123654", " -2.8", " 156");
 
     showStudent();
     //...
    return 0;
} 
 

There is also a setting called protected:. If you are interested, you could go to www.cplusplus.com's tutorial or you could ask here.
For your second question, could you please explain that a little bit more, I don't quit understand what you are asking.

[me001]

well i understand the protected thing..isnt that the same thing as private?? but what i was trying to say before ( sorry about that) was about the person1 and person2 and all of the function uses within main (). the errors that are coming up are only about them not being declared. where would i declare them--i though i already did. and below is my updated program. if you notice where the setName function is, i tired a couple ways but they were really long errors. do you know how to do them?

#include <iostream>
#include <fstream>
#include <iomanip>
 
using namespace std;
 
class Student
{
      private:
              char lastname[40];
              char firstname[40];
              char ID[10];
              double GPA;
              int Score;
      public:
              Student(char [], char [], char [], double , int);
              void showStudent();
              void setName(char [], char []);
              void setID(char []);
              int  setGPA(double );
              int  setScore(int );
              char getDecision();
 
};
 
int main()
{
     char lastname[40];
     char firstname[40];
     char ID[10];
     double GPA;
     int Score;
  //...
}

thank you!!

[ilikepython]

well i understand the protected thing..isnt that the same thing as private?? but what i was trying to say before ( sorry about that) was about the person1 and person2 and all of the function uses within main (). the errors that are coming up are only about them not being declared. where would i declare them--i though i already did. and below is my updated program. if you notice where the setName function is, i tired a couple ways but they were really long errors. do you know how to do them?

#include <iostream>
#include <fstream>
#include <iomanip>

using namespace std;

class Student
{
private:
char lastname[40];
char firstname[40];
char ID[10];
double GPA;
int Score;
public:
Student(char [], char [], char [], double , int);
void showStudent();
void setName(char [], char []);
void setID(char []);
int setGPA(double );
int setScore(int );
char getDecision();

};

int main()
{

return 0;
}


thank you!!

Oohh, I think I got it. You are saying "showStudent();", you need to specify the object like this:

person1.showStudent();
person2.showStudent();
 

That should work.
Can't believe I missed it though.

Also, try to only post the code from your porgram that is relevant to your question. You don't have to keep posting every single function.

[me001]

but the person1 and person2 are not part of the class. we were suppose to declare them in int main() only.

here are the directions to the program..i got most of it, but do i have to do the "calling part" two times for each person?

Declare one Student with your name, your Z-ID, and some valid GPA and score.
Declare a second Student with some name, id, and an invalid GPA and invalid score.
For the first (valid) Student:

1. Call showStudent()
2. Call setName() to change just the first name, then call showStudent() again.
3. Call setName() again, changing both names, then call showStudent() again.
4. Call setID() to change the ID, then call showStudent() again.
5. Call setScore() to change the score to a new valid score. Display the value of the return code from the function. Then call showStudent() again.
6. Call setScore() to change the score to a new invalid score. Display the value of the return code from the function. Then call showStudent() again.
7 and 8. Call setGPA() twice, once with a valid new GPA and once with an invalid one. Each time, display the value of the return code from the function and then call showStudent() again.
9. Call and display the result from getDecision().

[AdrianH]

Hi me001,

I apologise for erasing most of your code, but if you look at the posting guidelines, it states to post only relevant sections. As you are new to C++, this may be a little difficult, but here are some tips:

• When you compile, you will be given file names and line numbers where the errors/warnings occur. Post these along with the line where the problem occurred. Actually, don’t just post the one line, but with a bit of context. The amount of context could be up to the beginning of the function with supporting class(es).
  
• It is a good idea to break the problem down in to smaller pieces so that you can post something that is compliable, but contains only what is necessary to replicate the error that you are having. In fact, by doing this, you will be more than halfway there to figuring out what the problem is yourself.
  
• Keep your functions small to make debugging it easier. The less irrelevant information in the function the better. In fact, a function should contain no irrelevant information, as that adds to the noise, making your function harder to read and debug (what you have done is right on the money there ;)).
  
• If it becomes necessary for someone to ask you for the entire code base, please Private Message (PM) it to the party asking for it.

All of these points will actually help you in learning how to debug your code yourself.

As, for the problems you are having, ilikepython is correct about the access modifiers for the class. You need to define the interface that is to be used by all as public. Included in (but not limited to) those are your constructors. (There are times that you will want to make your constructors private, but this is not one of them).

It looks like you have some training in another language, perhaps VB where you do not have to declare a variable before use and are mixing up the syntaxes. I say that because of this:

     Person1 = ( " Stanko", " Bree", " Z146926", " 3.3", " 1598");
 

There are also no variants in C/C++ (well not without using the C/C++ constructs). So what you need to do is declare the variable with its associated type, the construction parameters go with the variable name, like this:

     Student Person1( " Stanko", " Bree", " Z146926", " 3.3", " 1598");
 

This same problem occurs in several other parts of your code.

Those two are the biggest problems that I see in your code. If you wish to get further help, fix those errors, recompile and try to work within the posting guidelines. Using the tips I provided will also help.

Good luck. We will be here if you need us.

Ciao,


Adrian

[me001]

ok--sorry about that. i am actually new to the whole thing of programming--i am an engineering major. but when i do what you said...this is the error i recieve:

no matching function for call to `Student::Student(const char[8], const char[9], const char[8], const char[4], const char[5])'

i really do not undertsand this--why are they const char[8]..when i declared them as [40],[ 40], and [10]?

thank you

[ilikepython]

ok--sorry about that. i am actually new to the whole thing of programming--i am an engineering major. but when i do what you said...this is the error i recieve:

no matching function for call to `Student::Student(const char[8], const char[9], const char[8], const char[4], const char[5])'

i really do not undertsand this--why are they const char[8]..when i declared them as [40],[ 40], and [10]?

thank you

In your class you declared the constructor as:

Student(char [], char [], char [], double, int);
 

but I believe you called the last two arguements as strings. Try calling them without the quotes and see what happens.
The fact that the compilers says the char [] has less items than 40 just means that you called it with less than 40.

[AdrianH]

ok--sorry about that. i am actually new to the whole thing of programming--i am an engineering major. but when i do what you said...this is the error i recieve:

no matching function for call to `Student::Student(const char[8], const char[9], const char[8], const char[4], const char[5])'

i really do not undertsand this--why are they const char[8]..when i declared them as [40],[ 40], and [10]?

thank you

That is because there is no Student constructor with the signature you are using.

Student(char [], char [], char [], double , int); //< This is the signature

Student Person1( " Stanko", " Bree", " Z146926", " 3.3", " 1598"); //< This has 5 char arrays.

The sizes of the arrays are coming from the call. A C-string contains one char per letter plus one char for the terminating null character. Get rid of the quotes around your numbers, and the the call will match the signature.

I may not be in from the rest of the night. Don't worry, there are other people in the group who are capable like ilikepython.

Ciao,


Adrian

[me001]

When I do that I have to declare every single thing within the parenthesis. The two people should be declared separately from the constructor as I showed within the instructions above. Right now I am just very confused, but thank you for your quick responses. I appreciate it.

[ilikepython]

When I do that I have to declare every single thing within the parenthesis. The two people should be declared separately from the constructor as I showed within the instructions above. Right now I am just very confused, but thank you for your quick responses. I appreciate it.

You declare the "people" in main; they are instances of your Student class. You use the constructor to initialize their varaibles (lastname, firstname etc...). This:

Student myStudent("john", "smith", "Z1758294, 3.4, 1589);
 

makes an instance of the Student class. (using the constructor).
The paranthesis indicate the arguements passed to the constructor.
I'm sorry if I didn't explain this correctly or if I didn't understand your question, so if you need more help, just post here.

[me001]

thats what i have had the whole time but this is the error message i recieve:
no matching function for call to `Student::Student(const char[7], const char[8], const char[8], const char[4], const char[5])'

candidates are: Student::Student(const Student&)

Student::Student(char*, char*, char*, double, int)

[ilikepython]

thats what i have had the whole time but this is the error message i recieve:
no matching function for call to `Student::Student(const char[7], const char[8], const char[8], const char[4], const char[5])'

candidates are: Student::Student(const Student&)

Student::Student(char*, char*, char*, double, int)

Oh I'm sorry that's a typo on my part. Try this:

Student student("john", "smith", "Z17491", 3.4, 1589);
 

I forgot the closing quote on the ID number.

[me001]

i know i already had it--i am still getting the same error message.

[AdrianH]

i know i already had it--i am still getting the same error message.

Ok, can you post that part of main() which creates the instances of Student? I'm pretty sure what we have here is a failure to communicate. ;)


Adrian