Welcome! This Scala lesson demystifies two key features: named arguments and default parameter values. They make function calls clearer and the code more maintainable.

Named arguments enhance code readability by associating each argument with a parameter name, thereby eliminating the need to remember their order. When using named arguments, you can place them in any order during the function invocation.

Imagine you're drawing a rectangle:

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1def drawRectangle(height: Int, width: Int, color: String): Unit =
2    println(s"Drawing a rectangle of height $height, width $width, and color $color")
3
4@main def run: Unit =
5    drawRectangle(height = 5, color = "blue", width = 10)
6    drawRectangle(height = 5, width = 10, color = "blue")
7    drawRectangle(color = "blue", width = 10, height = 5)

Named arguments make function invocations self-explanatory, reducing errors and improving readability.

Default parameter values automatically assign a predefined value to a function parameter. They permit the skipping of parameters that aren't required for the function call.

Consider a function that greets a user:

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1def greetUser(name: String = "Guest"): Unit =
2    println(s"Hello, $name")
3
4@main def run: Unit =
5    greetUser()                  // Displays "Hello, Guest"
6    greetUser("John")            // Displays "Hello, John"
7    greetUser(name = "Emily")    // Displays "Hello, Emily"

The first function call uses the default value, as no argument is passed.

The combination of both concepts brings flexibility and clarity.

Let's modify the drawRectangle function, adding a default color:

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1def drawRectangle(height: Int, width: Int, color: String = "Red"): Unit =
2    println(s"Drawing a rectangle of height $height, width $width, and color $color")
3
4@main def run: Unit =
5    drawRectangle(height = 20, width = 30)                      // color is "Red"
6    drawRectangle(height = 20, color = "Blue", width = 30)      // color is "Blue"

Excellent work! We've expanded our function toolkit by learning about named arguments and default parameter values. These features simplify function calls, thereby improving your Scala expertise.

Now, it's time for hands-on practice tasks to solidify your understanding. The combination of learning and practice is key to mastery in coding. So, let's start coding!