Why some methods cannot be called with Rounded bracket in Scala

Question

Here is the example. I would like to know why I am not able to use Rounded Bracket (()) to call the toFloat method

This works : toFloat

scala> val no = "8.5".toFloat
no: Float = 8.5

This DO NOT work : toFloat()

scala> val no = "8.5".toFloat()
<console>:27: error: Float does not take parameters
         val no = "8.5".toFloat()
                               ^

See http://docs.scala-lang.org/style/naming-conventions#parentheses — jub0bs, Apr 30 '16 at 20:50

score 4 · Accepted Answer · edited Jun 20 '20 at 09:12

The method StringLike.toFloat is defined as:

def toFloat: Float = java.lang.Float.parseFloat(toString)

The documentation says the following in regards to parenthesis:

Parentheses

Unlike Ruby, Scala attaches significance to whether or not a method is declared with parentheses (only applicable to methods of arity-0).

For example:

def foo1() = ...

def foo2 = ...

These are different methods at compile-time. While foo1 can be called with or without the parentheses, foo2 may not be called with parentheses.

This goes to show that if a method is declared without parenthesis they may not be added during invocation.

Why some methods cannot be called with Rounded bracket in Scala

1 Answers1

Parentheses