[chrisseaton]

Wow can you really write

    val e = p | e

in Scala? How does that work with eager evaluation?

[hrjet]

It's not eager. The | combinator takes lazy parameters (called pass-by-name in scala). So it essentially gets translated to:

val e = operator_pipe(() => p, () => e)

Note that the operator_pipe() itself returns a function, which gets assigned as a value to `e`. So there is lots of implicit laziness.