A partially applied function is an expression in which you don't supply all of the arguments needed by the function. Instead, you supply some, or none, of the needed arguments. For example, to create a partially applied function expression involving sum,

scala> def sum(a: Int, b: Int, c: Int) = a + b + c
sum: (a: Int,b: Int,c: Int)Int

in which you supply none of the three required arguments, you just place an underscore after "sum". The resulting function can then be stored in a variable. Here's an example:

scala> val a = sum _
a: (Int, Int, Int) => Int = 

Read more: Partially applied functions

partially applied functions

Scala allows you to indicate that the last parameter to a function may be repeated. This allows clients to pass variable length argument lists to the function. To denote a repeated parameter, place an asterisk after the type of the parameter. For example:

  scala> def echo(args: String*) = 
           for (arg <- args) println(arg)
  echo: (String*)Unit

Defined this way, echo can be called with zero to many String arguments:

  scala> echo()
  
  scala> echo("one")
  one
  
  scala> echo("hello", "world!")
  hello
  world!

Read more: Repeated parameters

functions

Syntax:
    Expr1 ::=  ‘return’ [Expr]

An apply method which is generated by the compiler as an expansion of an anonymous function does not count as a named function in the source program, and therefore is never the target of a return expression.
Returning from a nested anonymous function is implemented by throwing and catching a scala.runtime.NonLocalReturnException. Any exception catches between the point of return and the enclosing methods might see the exception. A key comparison makes sure that these exceptions are only caught by the method instance which is terminated by the return.
If the return expression is itself part of an anonymous function, it is possible that the enclosing instance of f has already returned before the return expression is executed. In that case, the thrown scala.runtime.NonLocalReturnException will not be caught, and will propagate up the call stack.

return type return statement NonLocalReturnException syntax