trouble

This is a discussion on trouble within the C++ Programming forums, part of the General Programming Boards category; i have a code that i want to ask you for a number than give you the pointer to the ...

  1. #1
    Registered User
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    Jun 2005
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    Post trouble

    i have a code that i want to ask you for a number than give you the pointer to the number and then ask you what you want the pointer to be changed to and it dosen work it wont compile without an error message

    Code:
    #include <iostream>
    
    using namespace std;
    
    int times,number,pointer;
    int *p;
    int main()
    {
        cout<<"how many time will we make a pointer?"<<endl;
        cin>> times;
        while( times >= 0 )
        {
               cout<<"I need a number:"<<endl;
               cin>> number;
               p = &number;
               cout<<"The ponter of "<<number<<" is: "<< p<<endl;
               cout<<"What will its new pointer be?"<<endl;
               cin>> *p;
               number = p;
               cout<<"the pointer of number is now "<< *number<<endl;
               times --;
        }
    }

  2. #2
    Registered User
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    > number = p;

    That is assigning a pointer value to an int variable. You probably mean this:

    number = *p;

    However, that is unnecessary because number and *p are always the same as long as p points to the address of number.

    In addition, when you output number, you don't need to use *number. It is just an int variable. I think you are getting confused between which variable is an int and which is a pointer.

  3. #3
    Tropical Coder Darryl's Avatar
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    you need to dereference the pointer here:
    Code:
    cout<<"The ponter of "<<number<<" is: "<< *p<<endl;
    and here
    Code:
    number = *p;
    However this last line is unecessary because
    Code:
    cin>> *p;
    already changed number.
    and finally, you can't dereference a variable, I would had thought you'd get an error
    Code:
    cout<<"the pointer of number is now "<< number << endl
    Now, I have a funny feeling you are trying to change the address of the pointer, if that is the case, don't, especially not by typing in some value willy nilly, you are asking for trouble. especially since you are then changing that value with the next cin. Big trouble!!

  4. #4
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    ok now i know how to change the pointer of a number and i know how to use a pointer but y would i need to know how to do this is ther any point to haveing many vareibles with the same pointer?

  5. #5
    Hardware Engineer
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    Sep 2001
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    1,398
    ...is ther any point to haveing many vareibles with the same pointer?
    Well, a pointer holds an address, and it can only point-to one variable at a time. When you define a variable, the compiler assigns an address to it. Each variable gets it's own address.

    But, say you have a character array (C-style string)... A pointer can point-to one character, then another.

    Or, you might have two different pointers which happen to be pointing to the same character in the string.

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