Scala’s ‘::’ operator, how does it work?

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From the Spec:

6.12.3 InfixOperations An infix operator can be an arbitrary
identifier. Infix operators have
precedence and associativity defined
as follows.

…

The associativity of an operator is
determined by the operator’s last
character. Operators ending in a colon
‘:’ are right-associative. All other
operators are left- associative.

You can always see how these rules are applied in Scala by printing the program after it has been through the ‘typer’ phase of the compiler:

scala -Xprint:typer -e "1 :: Nil"

val r: List[Int] = {
  <synthetic> val x$1: Int = 1;
  immutable.this.Nil.::[Int](x$1)
};

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