8.02 Pointer to Const vs Const Pointer & Placing Lookups in Microcontroller Flash ROM

#include <iostream>
using namespace std;

void noChange(const double* const someValue);

void noConst();
void cp2ncd();
void ncp2cd();
void cp2cd();



int main() {

	double* myDubz = new double(5.25);

	noConst();
	cout << endl;

	cp2ncd();
	cout << endl;

	ncp2cd();
	cout << endl;

	cp2cd();
	cout << endl;

	noChange(myDubz);

	delete myDubz;
	myDubz = nullptr;

	return 0;
}

void noChange(const double* const someValue) {
	cout << *someValue << endl;
}


//1. non-const pointer to non-const data
void noConst() {
	cout << "In noConst" << endl;

	int* intPtr = new int(50);
	cout << "\toriginal value:" << *intPtr << endl;

	*intPtr = 100;
	cout << "\tchanged data: " << *intPtr << endl;

	delete intPtr;

	intPtr = new int(125);
	cout << "\tnew int entirely: " << *intPtr << endl;

	delete intPtr;

}

// 2. const pointer to non-const data
void cp2ncd() {
	cout << "In cp2ncd" << endl;

	int* const intPtr = new int(100);

	cout << "\toriginal value: " << *intPtr << endl;

	*intPtr = 250;
	cout << "\tmodified value: " << *intPtr << endl;

	// intPtr = new int(222);   
	
	delete intPtr;
	
}

// 3. non-const pointer to const data
void ncp2cd() {
	cout << "In ncp2cd" << endl;

	const int* intPtr = new int(500);
	cout << "\toriginal value: " << *intPtr << endl;

	// *intPtr = 600;  

	delete intPtr;

	intPtr = new int(1000);  //pointer can change!
	cout << "\tnew value: " << *intPtr << endl;

	delete intPtr;
}

// 4. const pointer to const data
void cp2cd() {
	cout << "In cp2cd" << endl;

	const int* const intPtr = new int(5000);

	cout << "\toriginal value: " << *intPtr << endl;

	//  *intPtr = 6000;    // can't do this, the data is constant
	// intPtr = new int(6000);  //can't do this, the pointer is constant

	delete intPtr;
}