/* * Copyright (c) 2011-13 Miles Sabin * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package shapeless package ops import scala.collection.{ GenTraversable, GenTraversableLike } object traversable { /** * Type class supporting type safe conversion of `Traversables` to `HLists`. * * @author Miles Sabin */ trait FromTraversable[Out <: HList] { def apply(l : GenTraversable[_]) : Option[Out] } /** * `FromTraversable` type class instances. * * @author Miles Sabin */ object FromTraversable { import syntax.typeable._ implicit def hnilFromTraversable[T] = new FromTraversable[HNil] { def apply(l : GenTraversable[_]) = if(l.isEmpty) Some(HNil) else None } implicit def hlistFromTraversable[OutH, OutT <: HList] (implicit flt : FromTraversable[OutT], oc : Typeable[OutH]) = new FromTraversable[OutH :: OutT] { def apply(l : GenTraversable[_]) : Option[OutH :: OutT] = if(l.isEmpty) None else for(h <- l.head.cast[OutH]; t <- flt(l.tail)) yield h :: t } } }