Taken from Essential Scala by Noel Welsh and Dave Gurnell
Invariant: Foo[T]: Foo[A] and Foo[B] are unrelated regardless
of the relationship between A and B
Covariant: Foo[+T] -> Foo[A] is a supertype ofFoo[B] if A is a supertype of B.
Contravariant: Foo[-T] -> Foo[A] is a subtype of Foo[B] if A is a supertype of B.
| sealed trait Node { | |
| def print: String = | |
| this match { | |
| case Obj(v) => v.toString | |
| case JSONObj(v) => s"{\n${v.print}\n}" | |
| case Element(k, v) => s"""\t"$k": "${v.print}",\n""" | |
| case JSONEnd => "" | |
| case JSONPair(hd, tl) => s"${hd.print} ${tl.print}" | |
| case JSONSeq(hd, tl) => s"[ ${hd.print} ${tl.print} ]" | |
| } |
| httpPort: 7000 | |
| cacheDuration: 60 | |
| probeConnectionWaitInSeconds: 10 | |
| databases: | |
| - name: bobsDatabase | |
| user: system | |
| jdbcUrl: jdbc:oracle:thin:@localhost:1522:xe | |
| probes: | |
| - healthCheck | |
| - noLabels |