#include <iostream> //for input and output to the screen
#include <fstream> //for input and output to files
#include <cstdlib>
#include <string> //class for strings

using namespace std;

//Prototypes. It's important to have prototypes for your functions before you declare main.
void input();
void pointers();
void garbagecollection();

int main(){ //Just comment out the line that you want to run the tutorial.
//	input();
//	pointers();
//	garbagecollection();
}

void input(){

	string strinput;
	int intstring;

	cout << "We are testing how cin handles input. (enter ctrl-z to move on)" <<endl;
	//eof is true when the user enters ctrl-d (unix) or ctrl-z (windows)
	while (cin.eof() == false){
		cin >> strinput;
		cout << strinput << endl << "return to start of loop" << endl;
	}
	//that should have demonstrated that cin will stop at whitespaces

	cout << "Let's look at how strings work"<<endl;

	for (int i=0; i < strinput.length(); i++){
		cout << "strinput[" <<i << "] = " << strinput[i] <<endl;
	}
}

void pointers(){
	string input = "This is our test string"; //We have declared a string
	string *strptr; //We have declared a string pointer
	char* charptr; //A character pointer
	strptr = &input; //The ptr now points at the string. 
					 // The & operator returns the reference to the string
	char arrinput[25];
	int i;
		
	
	cout << "------------------------------------------------------"<<endl;
	cout << "This demonstrates how * and & work." << endl << endl;
	cout << "input contents: " << input << endl;
	cout << "&input: "<< &input << endl;
	cout << "*(&input): " << *(&input) << endl;
	cout << "strptr contents: " << strptr << endl;
	cout << "*strptr: " << *strptr << endl;
	cout << "&(*strptr): " << &(*strptr) << endl;
	cout << "input.length(): " << input.length() << endl;
	cout << "strptr->length(): "<< strptr->length() << endl;
	cout << "(*strptr).length(): "<< (*strptr).length() << endl;

	cout << "------------------------------------------------------"<<endl;
	cout << "Hopefully the above list gives you a good reference of what" <<endl;
	cout << "you can do with pointers and how to do it as well as the various" <<endl;
	cout << "ways of doing the same thing."<<endl;
	cout << "------------------------------------------------------"<<endl;
	cout << "The next question might be are there any cool things we can do with"<<endl;
	cout << "pointers that we couldn't do before? Of course!" <<endl;
	cout << "Pointer arithmetic: Let's get a new pointer, charptr and point it to "<<endl;
	cout << "the first character in the string." <<endl;

	for(i=0; i<input.length(); i++){
		arrinput[i] = input[i];
	}
	charptr = &(arrinput[0]);
	i=0;
	while (i<23){
        cout << "*charptr++: " << *(charptr++) << endl;
		i++;
	}
}

void garbagecollection(){
	string *strptr;

	//new is always called on the constructor and returns a pointer
	//delete is always called on a pointer
	cout << "As you are aware by now C++ does not have managed memory."<<endl;
	cout << "What does that mean to you? Well, C++ automatically calls"<<endl;
	cout << "destructor on variables once they go out of scope but if those"<<endl;
	cout << "variables are pointers then, if whatever they are pointer at was"<<endl;
	cout << "allocated dynamically (i.e. with new) then those destructors are not"<<endl;
	cout << "called and that memory isn't reclaimed till the program exists and the "<<endl;
	cout << "operating system runs it's garbage collection routines."<<endl;
	cout << "-------------------------------------------------------"<<endl;
	cout << "Let's see an example:"<<endl;
	{
		//create a new block so we can play with scoping
		string *strptr2 = new string();
		*strptr2 = "Another test string";
		cout << "*strptr2: " << *strptr2;
		strptr = strptr2; 
	}
	cout << "If we try to access strptr2 now we'll get an error because it's out of"<<endl;
	cout << "scope and has been destroyed. However, let's see what's in strptr"<<endl;
	cout << "*strptr: " << *strptr << endl<< endl;;
	cout << "See what I mean? However delete strptr will take care of this."<<endl;

	delete strptr;
	{
		//create a new block so we can play with scoping
		string *strptr2 = new string();
		*strptr2 = "Another test string \n";
		cout << "*strptr2: " << *strptr2;
		strptr = strptr2; 
		delete strptr2;
	}
	cout << "*strptr: " << *strptr << endl<< endl;;


}