10: Information Hiding

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Questions and Answers

What is the main purpose of information hiding in programming?

To improve the performance of the code

To expose all details of a data structure

To only allow private access to data members

To separate declarations from definitions (correct)

The header file should include both declarations and definitions of functions.

False

What is the purpose of the operator+ function in the rational struct?

To return the sum of two rational numbers.

In a rational struct, the variable 'd' must not equal ___ to maintain its invariant.

0 Signup and view all the answers

Match the following components of the rational struct with their descriptions:

int n = Numerator of the rational number int d = Denominator of the rational number operator+ = Function for adding two rationals operator- = Function for subtracting two rationals Signup and view all the answers

What does the 'struct rational' primarily represent?

An object that holds pairs of integers representing a fraction Signup and view all the answers

Encapsulation ensures that users understand how functions within a struct are implemented.

False Signup and view all the answers

What is a requirement for a rational number to be stored in a reduced form?

The numerator and denominator must have no common factors other than 1. Signup and view all the answers

The term ___ describes a programming technique to prevent users from accessing and modifying internal states directly.

encapsulation Signup and view all the answers

Which part of the struct declaration ensures that the denominator is never zero?

The invariant comment Signup and view all the answers

What does the function v.size() do in relation to vectors?

Returns the number of elements in the vector Signup and view all the answers

In C++, by default, all members of a class are public.

False Signup and view all the answers

What is the primary purpose of encapsulation in C++?

To hide the internal representation and expose only functionality. Signup and view all the answers

In the example provided, the class 'rational' uses two private members: an integer 'n' and an integer '____'.

d Signup and view all the answers

Match the following C++ access modifiers with their visibility type:

public = Accessible from anywhere private = Accessible only within the class protected = Accessible in derived classes default for struct = Accessible from anywhere Signup and view all the answers

Which of the following statements is true regarding the differences between structs and classes in C++?

Both structs and classes can have private members Signup and view all the answers

The internal representation of an object in a class should be visible to the user.

False Signup and view all the answers

What is one way to change the internal representation of a class without affecting user code?

By changing the representation of data types (e.g., polar to Cartesian coordinates). Signup and view all the answers

The principle of information hiding can be implemented in C++ using ____.

classes Signup and view all the answers

Match the following terms with their definitions:

Encapsulation = Hiding the internal state of an object Public = Members accessible from anywhere Private = Members only accessible within the class Struct = A variant of class with default public access Signup and view all the answers

What is the purpose of member functions in a class?

They allow access to private data members. Signup and view all the answers

Private members of a class can be accessed from outside the class directly.

False Signup and view all the answers

What must be checked before setting the denominator in the example provided?

The denominator value must not be zero. Signup and view all the answers

The __ function allows setting the numerator of a rational instance.

set_numerator Signup and view all the answers

Match the following member functions with their descriptions:

numerator = Returns the numerator of the instance set_numerator = Sets the numerator of the instance denominator = Returns the denominator of the instance set_denominator = Sets the denominator of the instance to a value and checks for zero Signup and view all the answers

Which of the following statements about class member functions is true?

They can access both public and private data members. Signup and view all the answers

In object-oriented programming, hiding data does not serve any useful purpose.

False Signup and view all the answers

What is a common misconception about information hiding in programming?

That it limits access to useful data. Signup and view all the answers

The class definition implies that 'd' must always be _____ while being set.

non-zero Signup and view all the answers

How can an instance of the class rational access member functions?

Using dot notation. Signup and view all the answers

What is the purpose of the const keyword in member function declarations?

To ensure the member function cannot change the instance's state Signup and view all the answers

The denominator of a rational number can be zero.

False Signup and view all the answers

What is the implicit parameter called that is accessible within member functions?

this Signup and view all the answers

In the member function declaration, _____ is used to prevent the modification of the instance.

const Signup and view all the answers

What will happen if a const object attempts to call a non-const member function?

An error will occur Signup and view all the answers

In a rational number, setting the numerator can always result in an error.

False Signup and view all the answers

What is the significance of the member function 'numerator()' in the rational class?

It returns the value of the numerator. Signup and view all the answers

When a member function is called, the expression with a value of class type is passed implicitly as _____ to the function.

this Signup and view all the answers

What does the statement 'int n = y.numerator();' demonstrate?

Accessing the numerator of a const object Signup and view all the answers

In C++, a class by default has all its members as private.

False Signup and view all the answers

What is enforced by the invariant in the rational struct?

The denominator 'd' must not equal zero. Signup and view all the answers

In C++, the keyword _____ is used to indicate a member function that does not modify the object.

const Signup and view all the answers

Match the following C++ keywords with their descriptions:

class = Defines a data type with methods and properties struct = Defines a simple data structure, usually with public members private = Specifies that class members are not accessible from outside the class public = Specifies that class members are accessible from outside the class Signup and view all the answers

Which of the following statements is true about the member function 'numerator()' in the rational class?

It returns the value of the numerator. Signup and view all the answers

An object of class rational can directly access its member variables without a member function.

False Signup and view all the answers

What does the struct rational contain as its members?

Two integers: n (numerator) and d (denominator). Signup and view all the answers

What is the default access modifier for members of a class in C++?

Private Signup and view all the answers

In C++, struct members are private by default.

False Signup and view all the answers

What keyword is used to declare a member function that does not modify the object?

const Signup and view all the answers

To access private members of a class from outside, you must use _____ members.

public Signup and view all the answers

Match the access modifiers with their visibility:

Public = Accessible from anywhere Private = Accessible only within the class Protected = Accessible within the class and its subclasses Internal = Accessible within the same package Signup and view all the answers

Which function call would give access to a private member from outside the class?

obj.memberFunction() Signup and view all the answers

Member functions can only be defined inside the class definition.

False Signup and view all the answers

The keyword _____ is used to ensure that functions in a class can only access their own members.

this Signup and view all the answers

Which of the following statements is true regarding member functions?

They can directly access private members of the class. Signup and view all the answers

Study Notes

Introduction to Computer Science Course Information

Course code: 252-0032, 252-0047, 252-0058
Authors: Manuela Fischer and Felix Friedrich
Department: Computer Science, ETH Zurich
Semester: Fall 2024

Information Hiding

A new type, like rational, is stored in a library.
Declaration and definition distinctions are made.
A header file (rational.h) holds declarations (Code 13.1).
An implementation file (rational.cpp) holds definitions (Code 13.2).

Encapsulation

Invariants need to be defended, i.e. rational.d != 0.
Users should be given the what not the how.
The internal representation can be changed without rewriting user code (e.g., polar to Cartesian coordinates).
A type is defined by its values and functionality, but representation is hidden.
Functionality is important, not the representation.
Encapsulation is offered in C++ via classes.

Classes

Classes use encapsulation in C++.
A struct's members are public by default.
Class members are private by default in C++.
Public members can be accessed outside the class.
Private members cannot be accessed outside the class.

Member Functions

Member functions can access private data.
Member functions can be public.
Accessing members happens using the syntax r.member_function().
const after a member function assures the object won't be changed.
Example: rational x; x.set_numberator(); const rational y = x; y.numerator();
Member functions can be declared in-class or out-of-class (Code 13.14, 13.15 and 13.16, separate declaration and definition files for classes can be used). Scope resolution (::) is required when defining a member function outside its class.

Constructors

Constructors are special member functions with the same name as the class.
They initialize class members.
They can be overloaded with different parameters.
If no constructor is provided, a default one is created. A default constructor initializes member variables using their default initialization values.
The assert(d != 0) is a critical check in the constructor to guarantee the invariant.
Default constructors can be deleted to prevent implicit creation (Code 13.7).

User-Defined Conversions

Converting from int to rational is allowed using a constructor, e.g., rational r = rational(2)
Implicit conversions are also possible, like rational s = 2.
Conversions to other types (e.g., double) can be defined using conversion operators (Code 13.9).

Containers and Iterators

Data structures for storing collections are called containers.
Containers: like std::vector, std::list, std::unordered_set, std::set are provided with associated iterators (like std::vector<int>::iterator). These iterators let one traverse container elements.
std::vector: Efficient index-based access; but inserting at/removing from arbitrary indices is potentially slower. It can contain the same element multiple times.
std::list: Efficient insertion and removal, but not index-based access and slower lookups. Similar to vectors, elements are in insertion order, but not sorted.
std::unordered_set: Efficient “element contained?” checks and insertion and removal. Elements do not maintain a specific order.
std::set: Elements are in order; slower insertions than std::unordered_set

Iterators

Used to iterate over containers efficiently.
The use of iterators decouples iterating over the container from how the container stores its data.
Can modify elements within the container (mutating iterators) or only access and use them (constant iterators). Example for (auto it = v.begin(); it!=v.end(); ++it) will traverse the container v. The examples neg(v.begin(), v.begin() + (v.size() / 2)); demonstrate functional approach.

Const Iterators

Guarantee read-only access to the container.
Necessary for accessing elements of a constant container (e.g const vector<int> v). Use v.cbegin() and v.cend() to get constant iterators.

Studying That Suits You

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Description

This quiz covers key concepts from the Introduction to Computer Science course, focusing on information hiding and encapsulation in C++. It explores the distinctions between declaration and definition, the purpose of header and implementation files, and the principles of encapsulation through classes in C++. Test your understanding of these foundational topics!

10: Information Hiding

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Podcast

Questions and Answers

What is the main purpose of information hiding in programming?

The header file should include both declarations and definitions of functions.

What is the purpose of the operator+ function in the rational struct?

In a rational struct, the variable 'd' must not equal ___ to maintain its invariant.

Match the following components of the rational struct with their descriptions:

What does the 'struct rational' primarily represent?

Encapsulation ensures that users understand how functions within a struct are implemented.

What is a requirement for a rational number to be stored in a reduced form?

The term ___ describes a programming technique to prevent users from accessing and modifying internal states directly.

Which part of the struct declaration ensures that the denominator is never zero?

What does the function v.size() do in relation to vectors?

In C++, by default, all members of a class are public.

What is the primary purpose of encapsulation in C++?

In the example provided, the class 'rational' uses two private members: an integer 'n' and an integer '____'.

Match the following C++ access modifiers with their visibility type:

Which of the following statements is true regarding the differences between structs and classes in C++?

The internal representation of an object in a class should be visible to the user.

What is one way to change the internal representation of a class without affecting user code?

The principle of information hiding can be implemented in C++ using ____.

Match the following terms with their definitions:

What is the purpose of member functions in a class?

Private members of a class can be accessed from outside the class directly.

What must be checked before setting the denominator in the example provided?

The __ function allows setting the numerator of a rational instance.

Match the following member functions with their descriptions:

Which of the following statements about class member functions is true?

In object-oriented programming, hiding data does not serve any useful purpose.

What is a common misconception about information hiding in programming?

The class definition implies that 'd' must always be _____ while being set.

How can an instance of the class rational access member functions?

What is the purpose of the const keyword in member function declarations?

The denominator of a rational number can be zero.

What is the implicit parameter called that is accessible within member functions?

In the member function declaration, _____ is used to prevent the modification of the instance.

What will happen if a const object attempts to call a non-const member function?

In a rational number, setting the numerator can always result in an error.

What is the significance of the member function 'numerator()' in the rational class?

When a member function is called, the expression with a value of class type is passed implicitly as _____ to the function.

What does the statement 'int n = y.numerator();' demonstrate?

In C++, a class by default has all its members as private.

What is enforced by the invariant in the rational struct?

In C++, the keyword _____ is used to indicate a member function that does not modify the object.

Match the following C++ keywords with their descriptions:

Which of the following statements is true about the member function 'numerator()' in the rational class?

An object of class rational can directly access its member variables without a member function.

What does the struct rational contain as its members?

What is the default access modifier for members of a class in C++?

In C++, struct members are private by default.

What keyword is used to declare a member function that does not modify the object?

To access private members of a class from outside, you must use _____ members.

Match the access modifiers with their visibility:

Which function call would give access to a private member from outside the class?

Member functions can only be defined inside the class definition.

The keyword _____ is used to ensure that functions in a class can only access their own members.

Which of the following statements is true regarding member functions?

Study Notes

Introduction to Computer Science Course Information

Information Hiding

Encapsulation

Classes

Member Functions

Constructors

User-Defined Conversions

Containers and Iterators

Iterators

Const Iterators

Studying That Suits You

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