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import scala.collection.mutable.{Buffer, ArrayBuffer}
class RichBuffer[T, B[U] <: Buffer[U]](buffer: Buffer[T]) {
def mymap[S](f: T => S)(implicit rv: B[S]): B[S] = {
buffer.foreach{ e =>
rv += f(e)
}
rv
}
}
object App {
def mymap2[T, B[U] <: Buffer[U], S](buffer: B[T], f: T => S)(implicit rv: B[S]): B[S] = {
buffer.foreach{ e =>
rv += f(e)
}
rv
}
def mymap3[T, B <: Buffer[T], S](buffer: B, f: T => T)(implicit rv: B): B = {
buffer.foreach{ e =>
rv += f(e)
}
rv
}
def mymap4[T, B[U] <: Buffer[U], S](buffer: B[T])(f: T => S) (implicit rv: B[S]): B[S] = {
buffer.foreach{ e =>
rv += f(e)
}
rv
}
def main(args: Array[String]): Unit = {
implicit def richBuffer[T, B[U] <: Buffer[U]](buffer: B[T]): RichBuffer[T, B] =
new RichBuffer[T, B](buffer)
implicit val rv: scala.collection.mutable.ArrayBuffer[Int] = new ArrayBuffer[Int]
val buf = new ArrayBuffer[Int]
(1 to 5).foreach(buf += _)
buf.mymap(x => x*x)
richBuffer(buf).mymap[Int](x => x*x)
richBuffer[Int, ArrayBuffer](buf).mymap[Int](x => x*x)
mymap2(buf, (x: Int) => x*x)
mymap2[Int, ArrayBuffer, Int](buf, (x: Int) => x*x)
// mymap3(buf, x => x*x) // compiler error
mymap3(buf, (x: Int) => x*x)
mymap4(buf)(x => x*x)
}
}
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