Good Afternoon,

I'm a little difficulty with this little program. The error is argument of type int (*)[5] is not incompatible with parameter of type double. I'm getting this error on

swapFour(&a, &b);

Here is the whole program code

double a =102.39, b=201.59; 
    double c=30.99, d=48.99; 
    double e=55.21, f=95.35; 
    //call swapFour with pointer type paramters
    cout<<"before calling swapFour(...), a is " << a << " and a is " <<a <<endl; 
    swapFour(&a, &b);                   //watch, we pass &x and &y to this function!!!!!! 
    cout<<"after calling swapOne(...), x is " << a << " and y is " <<b <<endl; 

    //call swapFive with reference type paramters
    cout<<"before calling swapFive(...), c is " << c << " and d is " <<d <<endl; 
    swapFive(c, d);                 //watch, we pass c and d to this function!!!!!! 
    cout<<"after calling swapFive(...), c is " << c << " and d is " <<d <<endl; 

    //call swapSix with value type paramters
    cout<<"before calling swapSix(...), e is " << e << " and f is " <<f <<endl; 
    swapSix(e, f);                  
    cout<<"after calling swapSix(...), e is " << e << " and f is " <<f <<endl;

Functions

//swapFour takes two pointer type parameters 
void swapFour(double * a, double * b)
{
    //watch carefully how we do the swaping. Compare this with swapTwo
    double tp; 
    tp = *a;                    
    *a = *b; 
    *b = tp; 
}

//swapFive takes two reference type parameters 
void swapFive(double & a, double & b)
{
    //watch carefully how we do the swaping. Compare this with swapOne
    double tp; 
    tp = a;                 
    a = b; 
    b = tp; 
}
//swapSix takes two pointer type parameters 
void swapSix(double a, double b)
{
    //watch carefully how we do the swaping
    double tp; 
    tp = a;                 
    a = b; 
    b = tp; 
}

I would really appreciated if anyone could help me fix this error.

Thank you

Hi poloblue,

Your function calls look fine to me, in as much as I don't see an obvious problem with the parameters you're passing, unless there's some way in which the code you posted doesn't represent what you're trying to compile (with the code wrapped in a main() function and suitable prototypes provided). Is there more than you've posted here?

Bob, here is the whole program

CPP file

#include <iostream>
#include <fstream>
#include <string>
#include <cstring>
#include <cmath> 
#include <cstdlib>
#include <iomanip>
#include <vector>                    //include vector class template

//define a const array size
const int SIZE = 35;                //class size                
const int COLUMN = 11;              //column size

#include "lab2380_1_head.h" 

using namespace std; 


int main( )
{

    /************************************************************************
     Part A: pointer declarations, operators:
             * : dereference operator
             & : address operator
             . : member selection operator
             ->: dereference member selection operator 
     ************************************************************************/
    //simple pointers
    int cat, dog;                       //two int vars
    int *intPtr;                        //an int pointer
    cat = 10; 
    dog = 20; 
    intPtr = &cat;                      //intPtr points to cat, i.e., intPtr has the address of cat
    cout << "cat is      " <<cat <<",  "
         << "dog is    " <<dog <<",  "
         << "intPtr is " <<intPtr<<",  "
         <<"*intPtr is " <<*intPtr<<endl; 

    dog = *intPtr;                      //get what is pointed by intPtr to dog
    *intPtr = 55;                       //change what is pointed by intPtr to 55

    intPtr = &cat;                      //intPtr points to cat, i.e., intPtr has the address of cat
    cout << "cat is      " <<cat <<",  "
         << "dog is    " <<dog <<",  "
         << "intPtr is " <<intPtr<<",  "
         <<"*intPtr is " <<*intPtr<<endl; 

    //structure/class pointers
    studentType jane, joe;              //two students
    studentType *ptr;                   //student pointer

    //using member selection operator . to access members of a structure/class
    jane.firstName="Alice";             //initilization
    jane.lastName="Smith";
    jane.grade='A'; 

    //using member selection operator . to access members of a structure/class
    joe.firstName="Alex";               //initilization
    joe.lastName="Black";
    joe.grade='B'; 

    ptr = &jane;                        //ptr points to jane

    //use dereference member selection operator . to access members of a structure/class
    cout << ptr->firstName <<"  " 
         << ptr->lastName  <<" got "
         << ptr->grade << endl; 

    ptr = &joe;                         //ptr points to joe

    //use dereference operator *, member selection operator ., and dereference member selection operator 
    //to access members of a structure/class
    cout << (*ptr).firstName <<"  " 
         << (*ptr).lastName  <<" got "
         << ptr->grade << endl; 


    /************************************************************************
     Part B: Pointer arithemtic, arrays vs. pointers
     ************************************************************************/
    //var declaration
    int a[5]={10, 20, 30, 40, 50};      //an int array of size 5
    studentType fun[3];                 //a studentType array of size 3
    int *myPtr;                         //an int pointer
    studentType *yourPtr;               //a studentType point
    int i;                              //loop var

    //array name is a pointer pointing to the first element of the array
    //use array name pointer to access array elements
    cout<<"use array name ............ "<<endl; 
    for (i=0; i<5; i++)
    {
        cout<< *(a+i) <<" ";            //a+i is &a[i], *(a+i) is a[i]
    }
    cout<<endl; 

    myPtr = a; 
    cout<<"*myPtr = *a = a[0] = " << *myPtr<<endl; 
    myPtr = &a[1]; 
    cout<<"*myPtr = *(a+1) = a[1] = " << *myPtr<<endl;
    cout<<"What is *&a[2]? "         <<*&a[2]<<endl; 

    yourPtr = fun;                      //youPtr points to the first element of fun array
    for (i=0; i<3; i++)
    {
        cout<<"Enter a first name => "; 
        cin>> (yourPtr+i)->firstName;  
        cout<<"Enter a last name => ";    //changed by sirisha
        cin>> (*(yourPtr+i)).lastName; 
        cout<<"Enter a grade => "; 
        cin>> yourPtr[i].grade;
    }
    //cout students
    yourPtr = fun; 
    for (i=0; i<3; i++)
    {
        cout << (yourPtr+i)->firstName <<"  "
             << (*(yourPtr+i)).lastName <<" got " 
             <<  yourPtr[i].grade <<endl;                   
    }

    /************************************************************************
     Part C: Pointer parameter vs reference parameters vs value parameter
     ************************************************************************/
    // var declaration
    int x =10, y=20; 
    int u=30, v=40; 
    int w=50, z=60; 
    //call swapOne with pointer type paramters
    cout<<"before calling swapOne(...), x is " << x << " and y is " <<y <<endl; 
    swapOne(&x, &y);                    //watch, we pass &x and &y to this function!!!!!! 
    cout<<"after calling swapOne(...), x is " << x << " and y is " <<y <<endl; 

    //call swapTwo with reference type paramters
    cout<<"before calling swapTwo(...), u is " << u << " and v is " <<v <<endl; 
    swapTwo(u, v);                  //watch, we pass u and v to this function!!!!!! 
    cout<<"after calling swapTwo(...), u is " << u << " and v is " <<v <<endl; 

    //call swapThree with value type paramters
    cout<<"before calling swapThree(...), w is " << w << " and z is " <<z <<endl; 
    swapThree(w, z);                    
    cout<<"after calling swapThree(...), w is " << w << " and z is " <<z <<endl; 


    /*******************************************************************************
     Part D: This part is for you to complete.
             a. Define a new struct type 
                bookType with members of title, author, isbn, and price.

                You shall add the definition of the bookType into the header fil 
                lab2380_1_head.h.

             b. Repeat Part A with variables of double type and bookTypes. 
             b. Repeat Part B with char type arrays and variables
             c. Repeat Part C with variables of bookType
     *******************************************************************************/
    //Write your code  is here

    /************************************************************************
     Repeat Part A: pointer declarations, operators:
             * : dereference operator
             & : address operator
             . : member selection operator
             ->: dereference member selection operator 
     ************************************************************************/
    //simple pointers
    double tom, jerry;                      //two double vars
    double *doublePtr;                      //an double pointer
    tom = 10; 
    dog = 20; 
    doublePtr = &tom;                       //doublePtr points to tom, i.e., doublePtr has the address of tom
    cout << "tom is      " <<tom <<",  "
         << "jerry is    " <<jerry <<",  "
         << "doublePtr is " <<doublePtr<<",  "
         <<"*doublePtr is " <<*doublePtr<<endl; 

    jerry = *doublePtr;                     //get what is pointed by doublePtr to jerry
    *doublePtr = 55;                        //change what is pointed by doublePtr to 55

    doublePtr = &tom;                       //doublePtr points to tom, i.e., doublePtr has the address of tom
    cout << "tom is      " <<tom <<",  "
         << "jerry is    " <<jerry <<",  "
         << "doublePtr is " <<doublePtr<<",  "
         <<"*doublePtr is " <<*doublePtr<<endl; 

    //structure/class pointers
    bookType twilight, computers;               //two books
    bookType *bptr;                 //book pointer

    //using member selection operator . to access members of a structure/class
    twilight.title="Computer Illuminated";              //initilization
    twilight.author="Smith";
    twilight.isbn= 1589635;
    twilight.price= 100.95;

    //using member selection operator . to access members of a structure/class
    computers.title="AI";               //initilization
    computers.author="Johnson";
    computers.isbn= 9876542;
    computers.price= 98.63;

    bptr = &twilight;                       //ptr points to twilight

    //use dereference member selection operator . to access members of a structure/class
    cout << bptr->title <<"  " 
         << bptr->author  <<"  "
         << bptr->isbn  <<" is "
         << bptr->price << endl; 

    bptr = &computers;                          //ptr points to computers

    //use dereference operator *, member selection operator ., and dereference member selection operator 
    //to access members of a structure/class
    cout << (*bptr).title <<"  " 
         << (*bptr).isbn  <<" is "
         << bptr->price << endl; 

    /************************************************************************
     Repeat Part B: Pointer arithemtic, arrays vs. pointers
     ************************************************************************/
    //var declaration
    char r[]={'A', 'B', 'C', 'D', 'E'};     //an char array of size 5
    bookType funct[3];                  //a studentType array of size 3
    char *bmyPtr;                           //an char pointer
    bookType *yrPtr;                //a bookType point
    int i;                              //loop var

    //array name is a pointer pointing to the first element of the array
    //use array name pointer to access array elements
    cout<<"use array name ............ "<<endl; 
    for (i=0; bmyPtr[i]; i++)
    {
        cout<< *(r+i) <<" ";            //r+i is &r[i], *(r+i) is r[i]
    }
    cout<<endl; 

    bmyPtr = r; 
    cout<<"*bmyPtr = *r = r[0] = " << *bmyPtr<<endl; 
    bmyPtr = &r[1]; 
    cout<<"*bmyPtr = *(r+1) = r[1] = " << *bmyPtr<<endl;
    cout<<"What is *&r[2]? "         <<*&r[2]<<endl; 

    yrPtr = funct;                      //yrPtr points to the first element of funct array
    for (i=0; i<3; i++)
    {
        cout<<"Enter the title of a book => "; 
        cin>> (yrPtr+i)->title;  
        cout<<"Enter the author of the book => "; //changed by sirisha
        cin>> (*(yrPtr+i)).author; 
        cout<<"Enter the isbn of the book => "; 
        cin>> yrPtr[i].isbn;

    }
    //cout books
    yrPtr = funct; 
    for (i=0; i<3; i++)
    {
        cout << (yrPtr+i)->title <<"  "
             << (*(yrPtr+i)).author <<" got " 
             <<  yrPtr[i].isbn <<endl;                  
    }

    /************************************************************************
     Repeat Part C: Pointer parameter vs reference parameters vs value parameter
     ************************************************************************/
    // var declaration
    double a =102.39, b=201.59; 
    double c=30.99, d=48.99; 
    double e=55.21, f=95.35; 
    //call swapFour with pointer type paramters
    cout<<"before calling swapFour(...), a is " << a << " and a is " <<a <<endl; 
    swapFour(&a, &b);                   //watch, we pass &x and &y to this function!!!!!! 
    cout<<"after calling swapOne(...), x is " << a << " and y is " <<b <<endl; 

    //call swapFive with reference type paramters
    cout<<"before calling swapFive(...), c is " << c << " and d is " <<d <<endl; 
    swapFive(c, d);                 //watch, we pass c and d to this function!!!!!! 
    cout<<"after calling swapFive(...), c is " << c << " and d is " <<d <<endl; 

    //call swapSix with value type paramters
    cout<<"before calling swapSix(...), e is " << e << " and f is " <<f <<endl; 
    swapSix(e, f);                  
    cout<<"after calling swapSix(...), e is " << e << " and f is " <<f <<endl; 
    //well done and exit
    return 0; 
}

Header file

#include <iostream>
#include <cstring>
#include <string>
#include <vector> 

using namespace std; 

#ifndef     LAB2380_1_HEAD_H        
#define     LAB2380_1_HEAD_H


//define studentType structure
struct studentType 
{
    string firstName,                   //firstnames for students
           lastName;                    //last names for students
    char   grade;                       //letter grades
}; 

//define bookType structure
struct bookType
{
    string title,                       //titles for books
           author;                      //authors for books
    int isbn;                           //isbns for books
    double price;                       //prices for books
};

//swapOne takes two pointer type parameters 
void swapOne(int * x, int * y)
{
    //watch carefully how we do the swaping. Compare this with swapTwo
    int temp; 
    temp = *x;                  
    *x = *y; 
    *y = temp; 
}

//swapTwo takes two reference type parameters 
void swapTwo(int & x, int & y)
{
    //watch carefully how we do the swaping. Compare this with swapOne
    int temp; 
    temp = x;                   
    x = y; 
    y = temp; 
}
//swapThree takes two pointer type parameters 
void swapThree(int x, int y)
{
    //watch carefully how we do the swaping
    int temp; 
    temp = x;                   
    x = y; 
    y = temp; 
}

//swapFour takes two pointer type parameters 
void swapFour(double * a, double * b)
{
    //watch carefully how we do the swaping. Compare this with swapTwo
    double tp; 
    tp = *a;                    
    *a = *b; 
    *b = tp; 
}

//swapFive takes two reference type parameters 
void swapFive(double & a, double & b)
{
    //watch carefully how we do the swaping. Compare this with swapOne
    double tp; 
    tp = a;                 
    a = b; 
    b = tp; 
}
//swapSix takes two pointer type parameters 
void swapSix(double a, double b)
{
    //watch carefully how we do the swaping
    double tp; 
    tp = a;                 
    a = b; 
    b = tp; 
}

#endif

I'm getting this error while I compile the program

char' differs in levels of indirection from 'int [5]

Here:

83. int a[5]={10, 20, 30, 40, 50}; //an int array of size 5

268. double a =102.39, b=201.59; 

Looks like you've used the same name twice for two different variables, both named 'a'.

Hope that helps.

Now you know why you should use variable names that make sense. Just choosing random letters obviously have drawbacks.

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