Scala Functions and Graphs Quiz

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Questions and Answers

Which definition is utilized when executing the expression `(dots compose abs)(-3)`?

The first definition of `abs`.

The second definition of `abs1`.

A composition of `abs` and `dots`. (correct)

None of the above.

What will be the output of `shorten("Functional Programming", 20)`?

Functional Programmin...

Functional Programming

Functional Progra... (correct)

Functional Programming...

What does the `abs1` function return when called with the argument `-3`?

Undefined

3 (correct)

-3

Which of the following expressions will produce the same result as `a.to(b)`?

a --> b Signup and view all the answers

What result does `(abs andThen dots)(-3)` produce?

3... Signup and view all the answers

What type of data structure is created when `Edge(a, b)` is called?

Edge Signup and view all the answers

What will be the output of the function call `formatMessage("hello", "Joe")`?

Joe: hello Signup and view all the answers

What is the return value of the expression `average(1.0, 2.3, 4.5)`?

3.8 Signup and view all the answers

Which form of calling the `average` function utilizes variable-length argument lists?

average(1.0, nums*) Signup and view all the answers

What is the type of the parameter for the `first` function?

(A, B) Signup and view all the answers

What will the result of `first((1, 2)) - 10` be?

-9 Signup and view all the answers

Study Notes

Functional Programming Concepts

Absolute Value Function: Defined using an if-else expression to return the positive version of an integer. Example: def abs(x: Int): Int = if x > 0 then x else -x.
String Repetition: The function dots(length: Int) generates a string consisting of dots based on the specified length, achieved through string multiplication: "." * length.

Functional Composition

Function Composition: Utilizes (dots compose abs)(-3) to apply abs first and then dots on the result.
Function Chaining: (abs andThen dots)(-3) applies abs and then passes the output to dots, demonstrating another method of combining functions.

Graph Structure

Graph Class Definitions:
- class Edge(from: Node, to: Node) defines a connection between nodes.
- class Node features methods for creating edges:
  - infix def to(that: Node): Edge allows an infix style for establishing edges.
  - def --> (that: Node): Edge enables a more natural syntax for connecting nodes.

Node Interactions

Examples of creating nodes (val a = Node(); val b = Node()) and connecting them using both defined methods: a.to(b) and a --> b demonstrate multiple ways to establish relationships between nodes.

String Manipulation

String Shortening Function: def shorten(str: String, maxLen: Int): String truncates a string if its length exceeds maxLen, appending "..." to indicate truncation.
Extension Methods: An extension method to simplify the shortening process can be added, allowing strings to call the short function directly, e.g., "Functional Programming".short(20).

Alternatives for Absolute Value

Enhanced Absolute Value Implementation:
- abs1 uses a local max function to calculate the maximum value between the input and its negation: def abs1(x: Int): Int = def max(a: Int, b: Int) = if a > b then a else b.
- abs2 uses a more closure-like approach by defining maxX, which compares the input value against its negation: def abs2(x: Int): Int = def maxX(a: Int) = if a > x then a else x.

Each method showcases different programming paradigms within functional programming, such as higher-order functions, method overloading, and the usage of extensions for adding functionality to existing types.

String Formatting Function

formatMessage function creates a formatted message string with optional user prefix and newline.
Takes three parameters: msg (String), user (String, default "") and withNewline (Boolean, default true).
Utilizes StringBuilder for string construction for efficiency.
If user is provided and non-empty, it appends user: to the message.
Appends msg to the constructed string.
Depending on withNewline, a newline character can be added after the message.

Usage Examples

formatMessage("hello") returns "hello\n".
formatMessage("hello", "Joe") returns "Joe:hello\n".
formatMessage("hello", "Joe", false) returns "Joe:hello" (no newline).
Using named parameters for clarity, e.g., formatMessage("hello", "Joe", withNewline = false).

Average Calculation Function

average function computes the mean of given numbers.
Takes first (Double) and a variable number of additional others (Double*).
Calculates the average as the sum of first and others divided by their total count (1 + length of others).

Usage Examples

average(1.0, 2.3, 4.5) returns 2.3 as the average.
average(1.0, 2.3) returns 1.65, averaging the two numbers.
average(10.0) returns 10.0, the average of a single number.
Can pass a list of numbers using the splat operator, e.g., val nums = List(2.3, 4.5); average(1.0, nums*).

Tuple Handling Functions

first_bad retrieves the first element of a tuple but is typed to Any, noting potential unsafe type handling.
first_better[A] is a type-safe version retrieving the first element of a tuple of the same type.
first[A, B] generically retrieves the first element from a tuple with two different types.

Example Usage of Tuple Functions

first((1, 2)) results in 1.
first(("chicken", "egg")).toUpperCase returns "CHICKEN".
first(("chicken", 2)).toUpperCase calls an unsafe operation due to mismatched types.

Higher-Order Functions

Functions like f[B, A] and g[T, U] demonstrate how to define higher-order functions that generically handle tuples while retrieving elements.
Notably, f((1, "X")) infers the types correctly as A and B.
Type parameters can be explicitly specified, e.g., f[String, Int]((1, "X")).

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Description

Test your knowledge on Scala functions, such as absolute value and string manipulation, alongside basic graph theory concepts. This quiz includes concepts like function composition and infix notation in Scala. Dive deep into the essence of programming with functional approaches and object-oriented structures.