/* This program demonstrates
 * 1. Arrays fo C++ string objects
 * 2. c++ string object functions
 * 3. Introduction to pointers
 *
 * We can declare arrays of C++ string objects. While their memory storage is quite
 * different from other conventional arrays. the rest of the array principles still
 * apply.
 * Their capacity is determined at compile time, they can be initialized with set
 * notation, we can iterate through them and use each "element" as ca complete C++
 * string object. When passed into a function, an individual C++ string object would
 * pass by value, but an array of C++ string objects would pass by address
 *
 * Pointers are variables that can hold the address of another variable.
 */

#include<iostream>
#include<cstring>
#include<string>
using namespace std;
int main()
{
    /* An array os C++ string objects */
    string stArray[10] = {"Spongebob", "Squidward"};

    /* In the C++ string object array, each "Element" is a C++ string object
     * which is internally a c-string. So, we can use the second, non-obvious, dimension
     * to access individual characters.
     */
    cout<<"Access individual characters, stArray[0][4]: "<< stArray[0][4]<<endl;
    cout<<"Access each row as a string object, stArray[1]: "<< stArray[1]<< endl;

    /* Using getline to read in each C++ string object */
    cout<<"Enter 5 strings: ";
    for(int i=2; i<7; i++)
        getline(cin,stArray[i]);

    char findThis[25],copy[100];

    /* A c-string will automatically convert to a C++ string object upon assignment
     * To convert a C++ string object to a c-string, we need to call the c_str()
     * member function of the C++ string object.
     */

    strcpy(copy, stArray[1].c_str());
    cout<<"Copied c-string: "<< copy<<endl;

    /* We can use the C++ string object functions on each element of the array of
     * C++ string objects.
     */
    cout<<"Enter the search string: ";
    cin.getline(findThis,100);
    for(int i=0; i<7; i++)
        if(stArray[i].find(findThis,0) < stArray[i].length())
            cout<<"found in string "<< i<<endl;

    /* A variable has 5 properties: type, size, name, value and address
     * We can store the address of a variable in another variable.
     * This new variable that contains the address of another variable is called a pointer
     * We declare pointer using the * operator.
     * We get the address of a variable using the & operator.
     */

    int var = 50;       // regular integer variable

    int *ptr;           // declare a pointer
    ptr = &var;         // Initialize it with teh address of x

    cout<<"var: "<< var <<endl;           //prints the value of var
    cout<<"Address of var: "<< &var <<endl;  //prints teh address of var
    cout<<"ptr: "<< ptr <<endl;      // prints the value of ptr, which is the address of var
    cout<<"Address of ptr: "<< &ptr <<endl;      // prints the address of ptr

    /* Dereferencing the pointer is the process of accessing a variable through
    * the pointer. When we use * along with the pointer anywhere except for
    * declaration, we are dereferencing.
    * When we dereference, we are getting the value of the variable whose address
    * is stored in the pointer.
    */
    cout<<"Dereferencing ptr: "<< *ptr <<endl;       // prints the dereferenced ptr,
    // which is the value of vqr

    int **q;        //Declare a two-level pointer
    q = & ptr;      //initialize q with the address of p

    cout<<"q: "<<q<<endl;       //prints q, which is the address of ptr
    cout<<"Address of q: "<<&q <<endl;          //prints the address of q
    cout<<"Dereference q: "<< *q <<endl;        //Prints q dereferenced, which is the value of ptr,
    // which is the address of var
    cout<<"Double dereference q: "<< **q <<endl;  //prints q double dereferenced,
    // which is dereferenced ptr, which is the value of var

    /* Null is the default 0 value for pointers, which signifies a pointer
     * pointing at nothing.
     * We can do it one of 3 ways.
     */
    ptr = NULL;     // c-style
    ptr = 0;
    ptr = nullptr;  // C++ style

    cout<<" Reached line 83"<<endl;

    //cout<< *ptr << endl; -> null pointer exception - will crash

    // We cannot assign pointers to integer literals
    //ptr = 0xffffcc3c;       // error

    /* Valid R-values for pointer assignment:
     * 1. Address of variables of the same type
     * 2. null
     * 3. pointer of the same type
     * 4. reinterpret cast
     */

    // We can assign a pointer to another pointer o the same type
    int *p2;
    int anothervar = 15;
    p2 = &anothervar;

    ptr = p2;
    cout<<"After re-assignment, *ptr: "<< *ptr<<endl;

    /* A reinterpret cast is a way to convert one type of pointer to another
     * The syntax is the same as static cast.
     * Here, we convert a pointer to a double to a pointer to an integer.
     */
    double y = 2.5;
    double *dblPtr = &y;
    // We cannot assign pointers across different types. We need to cast
    ptr = reinterpret_cast<int*>(dblPtr);

    cout<<"After reinterpret cast: ptr: "<<ptr<<endl;
    cout<<"*ptr: "<<*ptr<<endl;
    return 0;
}