14: Expression Trees (NOT RELEVANT TO EXAM)
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Questions and Answers

What is the main goal of expression trees?

  • To implement virtual functions
  • To enhance code modularity
  • To simplify memory allocation
  • To represent arithmetic expressions (correct)

Expression trees can only represent binary operators.

False (B)

What is one disadvantage of using a single node type for expression trees?

Memory wastage

The operator for a constant in an expression tree is represented as '__'.

<p>=</p> Signup and view all the answers

Match the following components of the expression tree with their descriptions:

<p>char op = Stores the operator double val = Holds the literal's value tnode* left = Points to the left operand tnode* right = Points to the right operand</p> Signup and view all the answers

Which of the following functions is responsible for evaluating an expression tree?

<p>eval (C)</p> Signup and view all the answers

The eval function is modular and does not require dissection of the node structure.

<p>False (B)</p> Signup and view all the answers

What does the presence of 'virtual' in a member function indicate?

<p>Dynamic binding occurs. (A)</p> Signup and view all the answers

Without the keyword 'virtual', the static type determines which function is executed.

<p>True (A)</p> Signup and view all the answers

What does the 'eval()' member function return in a Literal type?

<p>The value stored in the Literal object.</p> Signup and view all the answers

The class __________ is an abstract class since it does not implement the eval function.

<p>BinExp</p> Signup and view all the answers

Match the following classes to their descriptions:

<p>Literal = Stores a value and provides eval() Addition = Represents the addition of two expressions Times = Represents multiplication of two expressions BinExp = Base class for binary expressions</p> Signup and view all the answers

What is the purpose of the size() function in the Addition class?

<p>To return the total number of operands included. (C)</p> Signup and view all the answers

The 'Addition' class inherits both member variables and functions from the 'Exp' class.

<p>False (B)</p> Signup and view all the answers

What attributes does the BinExp class hold?

<p>Left and right operands (Exp* left, Exp* right).</p> Signup and view all the answers

To call the constructor of the base class in Addition, __________ is used.

<p>BinExp(l, r)</p> Signup and view all the answers

What is the significance of polymorphism in object-oriented programming?

<p>It allows one interface to represent different data types. (D)</p> Signup and view all the answers

Inheritance allows derived classes to completely replace the implementation of their parent classes.

<p>False (B)</p> Signup and view all the answers

What allows a dynamic type to determine which function is invoked during runtime?

<p>Polymorphism</p> Signup and view all the answers

In object-oriented programming, a class that inherits from another class is known as a __________.

<p>derived class</p> Signup and view all the answers

Match the concepts related to object-oriented programming:

<p>Polymorphism = Dynamic binding to functions Inheritance = Code reuse through parent-child relationships Subtyping = Type compatibility in a hierarchy Virtual function = Function that can be overridden</p> Signup and view all the answers

What does the Times::eval() method primarily do?

<p>Multiplies two evaluations (A)</p> Signup and view all the answers

The Times struct inherits from Exp.

<p>True (A)</p> Signup and view all the answers

What would need to happen for the Addition::eval() and Times::eval() methods to be unified?

<p>The concept of functional programming would need to be introduced.</p> Signup and view all the answers

The tnode structure includes members for a double value val and a character for the operation, represented by ___.

<p>op</p> Signup and view all the answers

Match the following structs with their corresponding operations and evaluations:

<p>Times = Multiplication of expressions Addition = Addition of expressions Cos = Evaluation of cosine function Literal = Direct value representation</p> Signup and view all the answers

Which operation is NOT directly implemented as a class derived from Exp?

<p>Power (D)</p> Signup and view all the answers

The tnode structure can handle unknown operators through its methods.

<p>False (B)</p> Signup and view all the answers

What is the purpose of the eval() method within the tnode structure?

<p>To evaluate the stored value</p> Signup and view all the answers

Functional programming concepts were deemed ___ for the current course's scope.

<p>outside</p> Signup and view all the answers

Which of the following best describes the inheritance structure in the provided code?

<p>Times is a subclass of Exp (B)</p> Signup and view all the answers

What does encapsulation in object-oriented programming primarily aim to achieve?

<p>Hiding implementation details from users (B)</p> Signup and view all the answers

A subtype can only support the same functionality as its supertype.

<p>False (B)</p> Signup and view all the answers

What does polymorphism allow in object-oriented programming?

<p>Using a single interface to represent different underlying data types.</p> Signup and view all the answers

The ______ section of a class contains members that are not accessible to users.

<p>private</p> Signup and view all the answers

Match the concepts with their descriptions:

<p>Encapsulation = Hiding implementation details Subtyping = Creating type hierarchies Polymorphism = Single interface for multiple classes Inheritance = Deriving new classes from existing ones</p> Signup and view all the answers

Which of the following is true about static dispatch in object-oriented programming?

<p>It resolves method calls at compile time. (A)</p> Signup and view all the answers

Private inheritance is a feature that lets derived classes inherit all public members of the base class.

<p>False (B)</p> Signup and view all the answers

What is the role of an abstract supertype in a type hierarchy?

<p>To define a common interface for subtypes.</p> Signup and view all the answers

In object-oriented programming, members that are accessible to users and provide functionality are defined in the ______ section.

<p>public</p> Signup and view all the answers

Which statement best describes multiple inheritance?

<p>It enables a subclass to inherit features from multiple classes. (A)</p> Signup and view all the answers

Flashcards

Expression Tree

A tree-like data structure representing arithmetic expressions.

Modularization

A technique for organizing code by separating concerns and making code more reusable.

Type Hierarchies

A hierarchy of classes where subclasses inherit properties and methods from parent classes.

Virtual Functions

Methods that can be overridden in subclasses, allowing different implementations for the same operation.

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Dynamic Binding

The process of determining the correct method to call at runtime based on the object's type.

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Code Reuse

The ability to reuse existing code by extending or modifying it.

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Concepts of Object-Oriented Programming

A set of principles and techniques for designing and writing software using object-oriented programming (OOP).

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String

A programming construct that groups multiple characters together, enclosed within double quotes, to represent text data.

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Inheritance

A type of object-oriented programming (OOP) technique that allows a subclass to inherit properties and methods from a parent class.

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Constructor

A type of function in OOP that is automatically called when an object of a class is created, used to initialize member variables.

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Polymorphism

Mechanism in OOP where different types of objects can be treated generically through a common interface, allowing for dynamic binding.

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Base Class

A class that defines a common set of properties and methods for other classes to inherit from.

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Derived Class

A class that inherits properties and methods from a base class, extending its functionalities.

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Abstract Class

A class that cannot be instantiated directly, used as a template for other classes, and often defines abstract methods that must be implemented by its subclasses.

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BinExp Class

A class in C++ that represents a binary expression, having a left and a right operand (both of type Exp).

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Times Class

A class in C++ that represents a multiplication operation, inheriting from the BinExp class. It has a left and right operand (both of type Exp) to multiply together.

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Times::eval()

A public member function of the Times class that evaluates the multiplication operation represented by the Times object. It performs the multiplication of the evaluations of the left and right operands.

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Literal Class

A class in C++ that represents a literal value (constant). It inherits from the Exp class and holds a double value.

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Addition Class

A class in C++ that represents an addition operation. It inherits from the Exp class and has a left and right operand (both of type Exp) to add together.

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Addition::eval()

A public member function of the Addition class that evaluates the addition operation represented by the Addition object. It performs the addition of the evaluations of the left and right operands.

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Cos::eval()

A public member function of the Cos class that evaluates the cosine operation represented by the Cos object. It calculates the cosine of the evaluation of the operand.

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Specialized Subtypes

Specialized subtypes are derived from a more general base type, inheriting common functionality but allowing for specific implementations. This reduces code redundancy and promotes code reusability.

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Overriding

Overriding is when a derived class provides its own implementation for a function that was inherited from the parent class, allowing specialized behavior.

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Encapsulation

Hiding implementation details of a type from users, exposing only a controlled interface for interaction.

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Subtyping

A subtype inherits all the capabilities of its supertype and can potentially add more.

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Static Dispatch

Non-virtual member functions are called based on the static type of the object at compile time.

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Overridden Member Function

A member function in a subtype that provides a different implementation than the one found in its supertype.

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Multiple Inheritance

A situation where a subtype inherits from multiple super types.

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Virtual Member Function

A member function that can be overridden in subtypes.

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Upcasting

The act of modifying an existing code base to use a super type instead of a subtype, leveraging polymorphism.

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Study Notes

Subtyping, Inheritance and Polymorphism

  • Subtyping, inheritance, and dynamic binding enable modularization through specialization
  • Inheritance enables sharing common code across modules, avoiding code duplication
  • The type hierarchy of expressions (e.g., Exp, Literal, Addition, Times) allows subtypes (e.g., Literal) to be used in places where supertypes (e.g., Exp) are expected
  • This is because of the subtype relation in the hierarchy
  • A variable of type Exp can hold expressions of different dynamic types, such as Literal or Addition
  • Polymorphism and dynamic dispatch are essential concepts in this context
  • Executed member functions of a subtype are determined by the dynamic type, not the static type in some cases

Expression Trees

  • Expression trees represent arithmetic expressions as a tree structure
  • Nodes in an expression tree include: literals, binary and unary operators, and function applications
  • Using a single node type for expression trees results in inefficiencies, like memory wastage
  • Alternate implementations lead to modular, less error-prone evaluation functions

Disadvantages of a Single Node Type

  • Every function must "dissect" the "sum" of all required nodes for evaluation
  • This approach is complex and error-prone, hindering code modularity

New Concepts Today

  • Subtyping
  • Polymorphism and dynamic dispatch

Polymorphism and Dynamic Dispatch

  • Variables of static type Exp can contain expressions of different dynamic types (e.g., Literal, Addition)
  • During execution, member functions for the dynamic type are executed, which promotes Polymorphism
  • The member functions execute according to their respective dynamic type, even though the static type is Exp
  • Using the dynamic type for the expression is called dynamic dispatch

Inheritance

  • Shared functionality among type hierarchy members is implemented only once
  • Examples of shared functionality are computing the size of binary expressions (e.g., Addition, Times)
  • Functionality is shared across subtypes using inheritance
  • Subtypes inherit functionality making it easier to extend the functionality given by the base class or super class

Syntax and Terminology

  • Specific structures (Exp, BinExp, Times) are defined as either types or subclasses
  • Relationships between types are specified, using the (public) keyword

Abstract Class Exp and Concrete Class Literal

  • Abstract class Exp defines members like size and eval (size=0;eval=0) which must be implemented by a concrete class and has no implementations, or concrete class methods, to fulfill the abstract class's structure for a specific dynamic type
  • A concrete class Literal implements methods size and eval

Literal Implementation

  • The implementation defines size as 1
  • The implementation defines eval as the value

Subtyping: A Literal is an Expression

  • A pointer to a subtype (Literal) can be used in place of a pointer to a super type (Exp)
  • But a pointer to a super type (Exp) cannot be used in place of a pointer to a subtype (Literal) in C++ programming

Polymorphism: A Literal Behaves Like a Literal

  • Dynamic types determine the member function to be executed
  • Dynamic binding is important in this context

Further Expressions and Operations

  • Additional expressions (e.g., -, /, √, cos, log) can be derived from the Exp base class
  • Examples are offered in the lecture materials through code demonstrations

Further Expressions: Addition and Times

  • Functionality for addition and multiplication of expressions is derived from a shared base class, BinExp, reducing code duplication

Extracting Commonalities - BinExp

  • Functionality related to operations on expressions is generalized from base class BinExp
  • Functionality associated with expressions is streamlined, using inheritance
  • Methods involving expression handling are commonly extracted

Inheriting Commonalities - Addition

  • The Addition class inherits core functionality from BinExp and provides its own implementation of the eval method to perform the addition operation

Inheriting Commonalities - Times

  • The multiplication operation is handled in a similar way for the Times object
  • This class inherits and implements a function override

Object-Oriented Programming Concepts

  • Encapsulation (weeks 10-13): Hiding implementation details, defining public interfaces for interaction
  • Subtyping (week 14): Type Hierarchies, defining relationships between general and specific types. A subtype can be used where a super-type is required and more features may be added
  • Polymorphism and dynamic binding (week 14): Using subtypes as if they were a supertype while handling different underlying functionality based on subtype at runtime.
  • Inheritance (week 14): Reduces code-duplication and promotes code reusability

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Lecture 14: Subtyping, Inheritance, and Polymorphism (PDF)

Description

Test your knowledge on expression trees, their structure, and evaluation processes. This quiz covers key concepts such as binary operators, evaluation functions, and class inheritance. Perfect for students learning about data structures and algorithms.

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