Open
Description
Proposed additions to object PartialFunction and object Option to provide a faster method for iterating over a largish collection of (Partial)Functions than orElse ... orElse ... orElse.
PartialFunction.liftChain():
/**
* Turn a collection of [[PartialFunction]]s into a virtual match expression. If the
* supplied collection is mutable, then changes after this call will be reflected in
* future invocations of the chained function.
*/
def liftChain[A, B](c: Iterable[PartialFunction[A, B]]): ((A) => Option[B]) = { x: A =>
// slow version: c.find(_.isDefinedAt(x)).map(_.apply(x))
// fast version:
var result: Option[B] = None
val i = c.iterator
while (result.isEmpty && i.hasNext) {
val func = i.next()
if (func.isDefinedAt(x))
result = Some(func(x))
}
result
}Option.chain():
/**
* Turn a collection of functions returning [[Option]] into a virtual match expression.
* If the supplied collection is mutable, then changes after this call will be reflected in
* future invocations of the chained function.
*/
def chain[A, B](c: Iterable[(A) => Option[B]]): ((A) => Option[B]) = { x: A =>
var result: Option[B] = None
val i = c.iterator
while (result.isEmpty && i.hasNext)
result = i.next().apply(x)
result
}