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

    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</p> Signup and view all the answers

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

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

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

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

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

    <p>True</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.</p> Signup and view all the answers

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

    <p>False</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.</p> Signup and view all the answers

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

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

    The Times struct inherits from Exp.

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

    The tnode structure can handle unknown operators through its methods.

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

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

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

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

    <p>False</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.</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</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.</p> Signup and view all the answers

    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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    Related Documents

    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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