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| class A | |
| class A2 extends A | |
| class B | |
| trait M[X] | |
| // | |
| // Upper Type Bound | |
| // | |
| def upperTypeBound[AA <: A](x: AA): A = x | |
| // equivalently, require a implicit parameter of <:<[AA, A]. | |
| // This technique must be used if A is an abstract type from the | |
| // enclosing scope. | |
| def upperTypeBound2[AA](x: AA)(implicit ev: AA <:< A): A = x // compiles to ev(x) | |
| // | |
| // Lower Type Bound | |
| // | |
| def lowerTypeBound[AA >: A](x: AA, pred: (AA => Boolean)): Boolean = pred(x) | |
| // equivalently, require a implicit parameter of <:<[A, AA]. | |
| // This technique must be used if A is an abstract type from the | |
| // enclosing scope. | |
| def lowerTypeBound2[AA >: A](x: AA, pred: (AA => Boolean))(implicit ev: A <:< AA): Boolean = pred(x) | |
| // | |
| // View Bound | |
| // | |
| def viewBound[AA <% A](x: AA): A = x | |
| //compiles to: | |
| def viewBound$[AA](x: AA)(implicit ev1$ : AA => A) = ev1$(x) | |
| // | |
| // Context Bound | |
| // | |
| def contextBound[X: M](x: X) = x; | |
| //compiles to: | |
| def contextBound$[X](x: X)(implicit ev1$ : M[X]) = x | |
| // In combination: | |
| def combo[AA <: A >: B <% String <% Int : M : Ordering] = 0 | |
| // compiles to: | |
| def combo[AA >: B <: A](implicit | |
| evidence$1: (AA) => String, | |
| evidence$2: (AA) => Int, | |
| evidence$3: M[AA], | |
| evidence$4: Ordering[AA] | |
| ): Int = 0 | |
| // | |
| // Usage | |
| // | |
| { | |
| { | |
| upperTypeBound(new A) | |
| upperTypeBound(new A2) | |
| } | |
| { | |
| val predA = (a: A) => true | |
| val predAny = (a: Any) => true | |
| lowerTypeBound(new A, predA) | |
| lowerTypeBound(new {}, predAny) | |
| } | |
| { | |
| implicit def String2A(s: String): A = new A | |
| viewBound("") | |
| } | |
| { | |
| implicit def MofA: M[A] = new M[A] {} | |
| contextBound(new A) | |
| } | |
| } |
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