Exercises

Checkpoint 22.16.1.

Write a function getPI that allocates a double on the heap, initializes the memory (or assigns it) to hold 3.14, and returns a pointer to the allocated memory.

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Checkpoint 22.16.2.

Write a function makeArray that allocates an array of 3 double on the heap, sets them to 1.1, 2.2, and 3.3, then returns a pointer to the array.

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Hint.

You can use {value, value, value} to initialize the array. Or you can do assignments to the three elements after creating it.

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Checkpoint 22.16.3.

Write a function makeBigArray that allocates an array of 100 double on the heap and sets them all to 5.0. It should then return a pointer to the array.

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Hint.

You will almost certainly need a loop to set all the elements of the array.

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Checkpoint 22.16.4.

The class NumberWrapper manages a single integer value on the heap. (Which is admittedly a kind of silly thing to do.)

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Implement the copy constructor for `NumberWrapper. It is declared inside the class, you will implement it outside the class (at line 36). It should make a deep copy of the managed memory.

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#include <iostream>

using namespace std;

class NumberWrapper {
public:
    NumberWrapper(int num);
    void setNum(int value);
    int getNum() const;
    ~NumberWrapper();

NumberWrapper(const NumberWrapper& other);
    NumberWrapper& operator=(const NumberWrapper& other);

private:
    int* m_myAddress; // Memory address of number we own
};

NumberWrapper::NumberWrapper(int num) {
    m_myAddress = new int(num);
}

void NumberWrapper::setNum(int value) {
    *m_myAddress = value;
}

int NumberWrapper::getNum() const {
    return *m_myAddress;
}

NumberWrapper::~NumberWrapper() {
    delete m_myAddress;
}

^^^!

//YOUR CODE HERE
===!
#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include "doctest.h"

TEST_CASE("copyConstructor") {
    NumberWrapper original(42);
    NumberWrapper copy(original);

CHECK(copy.getNum() == 42);
    
    copy.setNum(100);
    CHECK(original.getNum() == 42); // Original should remain unchanged
    CHECK(copy.getNum() == 100); // Copy should reflect the change
}

Hint 1.

m_myAddress is the memory address of the managed value. *m_myAddress is how you access the value from the heap. To get the value from other you can use other.getNum().

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Hint 2.

You do not need a loop, but you still will need to allocate new memory for the copy and then copy the value from the original object to the new one.

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Checkpoint 22.16.5.

The class NumberWrapper manages a single integer value on the heap. (Which is admittedly a kind of silly thing to do.)

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Implement the assignment operator `NumberWrapper. It is declared inside the class, you will implement it outside the class (at line 36). It should make a deep copy of the managed memory.

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Don’t forget to check for self-assignment! If you have a use after free error, it could be due to not handling self-assignment correctly.

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#include <iostream>

using namespace std;

class NumberWrapper {
public:
    NumberWrapper(int num);
    void setNum(int value);
    int getNum() const;
    ~NumberWrapper();

NumberWrapper(const NumberWrapper& other);
    NumberWrapper& operator=(const NumberWrapper& other);

private:
    int* m_myAddress; // Memory address of number we own
};

NumberWrapper::NumberWrapper(int num) {
    m_myAddress = new int(num);
}

void NumberWrapper::setNum(int value) {
    *m_myAddress = value;
}

int NumberWrapper::getNum() const {
    return *m_myAddress;
}

NumberWrapper::~NumberWrapper() {
    delete m_myAddress;
}

^^^!

//YOUR CODE HERE
===!
#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
#include "doctest.h"

TEST_CASE("assignmentOperator") {
    NumberWrapper original(42);
    NumberWrapper copy(100);

copy = original;
    CHECK(copy.getNum() == 42);

copy.setNum(200);
    CHECK(original.getNum() == 42); // Original should remain unchanged
    CHECK(copy.getNum() == 200); // Copy should reflect the change
}

TEST_CASE("assignmentOperator self assignment") {
    NumberWrapper original(42);

// self assignment... nothing should change
    original = original;

CHECK(original.getNum() == 42);
}

Hint 1.

m_myAddress is the memory address of the managed value. *m_myAddress is how you access the value from the heap.

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Hint 2.

You do not need a loop, but you still will need to allocate new memory for the copy and then copy the value from the original object to the new one.

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Welcome to Programming and Data Structures

Section 22.16 Exercises

Checkpoint 22.16.1.

Checkpoint 22.16.2.

Checkpoint 22.16.3.

Checkpoint 22.16.4.

Checkpoint 22.16.5.