Foundations of Software - LAMP - EPFL

The Alternative Combinator
� The alternative combinator P | Q succeeds if either P or Q
succeeds.
� It returns the result of P if P succeeds, or the result of Q, if Q
succeeds.
� The alternative combinator is implemented as a method of class
Parser.
def | (q : ⇒ Parser[T]) = new Parser[T] {
def apply(in : Input) = Parser.this(in) match {
case s1 @ Success( , ) ⇒ s1
case failure ⇒ q(in)
}
}
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