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eamelink/predicates.scala

Created June 25, 2014 16:06
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Composable predicates
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predicates.scala
class SimpleFile
class ExtendedFile extends SimpleFile
implicit class Predicate[-A](val fn: A => Boolean) {
def &&[B <: A](other: Predicate[B]): Predicate[B] = Predicate { (x: B) =>
fn(x) && other.fn(x)
}
}
val alwaysTrueSimple = (_: SimpleFile) => true
val alwaysTrueAdvanced = (_: ExtendedFile) => true
alwaysTrueSimple && alwaysTrueAdvanced
alwaysTrueAdvanced && alwaysTrueSimple
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