Java – Scala point syntax (or missing)

When I came across a piece of code that meant nothing to me, I was experiencing this wonderful book Programming in scala:

def above(that: Element): Element = {
    val this1 = this widen that.width
    val that1 = that widen this.width
    elem(this1.contents ++ that1.contents)
}

Notes 2 and 3:

val this1 = this widen that.width

It seems that I can use the following instead:

val this1 = this.widen that.width

However, when I try to compile this change, the following error occurs:

Why is this grammar unacceptable?

Solution

Line 2 uses the extension method as an operator instead of using it as a method in Java:

val this1 = this.widen(that.width)

The error occurred because you have omitted parentheses. You can only do this when using methods in operator symbols You cannot do this:

"a".+ "b" // error: ';' expected but string literal found.

Instead, you should write

"a".+ ("b")

In fact, you can do it with integers, but it's beyond the scope of this problem

Read more:

>Section 3 of Chapter 5 of your book is about operators. At least in the first edition and the fifth edition > a tour of scala: operators