Day 4 / Mar 4 (Fri)¶

Opening Questions¶

1. Are there any questions about the Scala topics covered?
2. What was the most important Scala feature that we covered during the last session?

Exercise: User Class¶

Define User class with greet method that says "Hello from $name" when executed.

Scala Topics¶

1. val vs def

   size("hello") // funkcja "hello".size // metoda

2. class User(name: String) vs class User(val name: String) (note name parameter)

git¶

• git installation on Windows 11
• git commmands
• init
• status
• add
• commit
• log
• diff (head..head~1, using commit shas)

Scala Topics¶

• scala.Predef
• Scaladoc
• String (it's java.lang.String)
• scala.collection.StringOps
• Higher-Order Functions (HOFs)
• filter
• sortBy
• foreach

• Underscore to mark unused input arguments to a function

  val size: String => Int = _ => 5

• assert

  assert(size("hello") == "hello".size)

  assert("hello".sortBy(c => c.toInt) == "ehllo") assert("hello".sortBy(_.toInt) == "ehllo")

• procedure vs method vs function

• methods = class members
• functions = standalone named executable block
• procedure = method that returns nothing (Unit)

Exercise: StringOps Favorities¶

Pick two methods of scala.collection.StringOps and use Scala Worksheet with sbt console to learn how to use them:

1. ++, concat
2. filter
3. drop
4. apply
5. sortBy
6. tail
7. foreach

Exercise: Convert function to method¶

Convert the f function to be a def to be used in filter.

val f: Char => Boolean = c => c != 'e' && c != 'o'

def f_def... = ???
"hello".filter(f_def) == "hll"

Exercise¶

Write last function that works like StringOps.last and uses the methods of StringOps we talked about today (except last).

val last: String => Char = ???

Hint: Use size and apply

Learning Scala¶

Working with the Learning Scala book, Chapter 8 "Classes".

Homework¶

Write nth function that returns the character at n-th position.

nth(s: String, n: Int): Char

Assume n as 0 <= n < s.length.

Breaks¶

1. 9:50 - 10:00
2. 11:00 - 11:10
3. 12:30 - 13:15 lunch break

Working Hours¶

Day: Mar 4 (Fri)

8:30am - 3pm remotely