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/*
* Copyright (c) 2011 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.examples
/**
* Record examples.
*
* @author Miles Sabin
*/
object RecordExamples extends App {
import shapeless._
import record._
import ops.hlist.ToList
import ops.record.{ Keys, Values }
import syntax.singleton._
def printBook[B <: HList, K <: HList, V <: HList](b : B)
(implicit
keys: Keys.Aux[B, K],
values: Values.Aux[B, V],
ktl: ToList[K, Any],
vtl: ToList[V, Any]) = {
(b.keys.toList zip b.values.toList) foreach { case (field, value) => println(field+": "+value) }
println
}
val book =
("author" ->> "Benjamin Pierce") ::
("title" ->> "Types and Programming Languages") ::
("id" ->> 262162091) ::
("price" ->> 44.11) ::
HNil
printBook(book)
// Read price field
val currentPrice = book("price") // Static type is Double
println("Current price is "+currentPrice)
println
// Update price field, relying on static type of currentPrice
val updated = book + ("price" ->> (currentPrice+2.0))
printBook(updated)
// Add a new field
val extended = updated + ("inPrint" ->> true)
printBook(extended)
// Remove a field
val noId = extended - "id"
printBook(noId)
}
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