What is the formal difference in Scala between braces and parentheses, and when should they be used?

Question

What is the formal difference between passing arguments to functions in parentheses () and in braces {}?

The feeling I got from the Pro

Answer 1

There is an effort from the community to standardize the usage of braces and parentheses, see Scala Style Guide (page 21): http://www.codecommit.com/scala-style-guide.pdf

The recommended syntax for higher order methods calls is to always use braces, and to skip the dot:

val filtered = tupleList takeWhile { case (s1, s2) => s1 == s2 }

For "normal" metod calls you should use the dot and parentheses.

val result = myInstance.foo(5, "Hello")