Sep 12, 2012
Scala Predef
Scala implicitly imports members of packages java.lang and scala, as well as the members of a singleton object named Predef, into every Scala source file. Predef, which resides in package scala, contains many useful methods. For example, when you say println in a Scala source file, you're actually invoking println on Predef. (Predef.println turns around and invokes Console.println, which does the real work.) When you say assert, you're invoking Predef.assert.
Programming in Scala, Second Edition
Martin Odersky (Author), Lex Spoon (Author), Bill Venners (Author)