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Questions and Answers
Which definition is utilized when executing the expression (dots compose abs)(-3)
?
What will be the output of shorten("Functional Programming", 20)
?
What does the abs1
function return when called with the argument -3
?
Which of the following expressions will produce the same result as a.to(b)
?
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What result does (abs andThen dots)(-3)
produce?
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What type of data structure is created when Edge(a, b)
is called?
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What will be the output of the function call formatMessage("hello", "Joe")
?
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What is the return value of the expression average(1.0, 2.3, 4.5)
?
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Which form of calling the average
function utilizes variable-length argument lists?
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What is the type of the parameter for the first
function?
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What will the result of first((1, 2)) - 10
be?
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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 applyabs
first and thendots
on the result. -
Function Chaining:
(abs andThen dots)(-3)
appliesabs
and then passes the output todots
, 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)
anda --> 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 exceedsmaxLen
, 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 localmax
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 definingmaxX
, 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 "") andwithNewline
(Boolean, default true). - Utilizes
StringBuilder
for string construction for efficiency. - If
user
is provided and non-empty, it appendsuser:
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 additionalothers
(Double*). - Calculates the average as the sum of
first
andothers
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 toAny
, 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 in1
. -
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]
andg[T, U]
demonstrate how to define higher-order functions that generically handle tuples while retrieving elements. - Notably,
f((1, "X"))
infers the types correctly asA
andB
. - 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.