这可以使用无形的 https://github.com/milessabin/shapeless图书馆的规模类型:
import shapeless._
def foo[A, N <: Nat](rect: Seq[Sized[Seq[A], N]]) = rect
val a = Seq(Sized(1, 2, 3), Sized(4, 5, 6))
val b = Seq(Sized(1, 2, 3), Sized(4, 5))
Now foo(a)
编译,但是foo(b)
没有。
这使我们能够编写非常接近您想要的界面的东西:
case class RectArray2D[A, N <: Nat](rows: Sized[Seq[A], N]*)
def processArray(arr: RectArray2D[Int, _]) = {
// Run-time confirmation of what we've verified at compile-time.
require(arr.rows.map(_.size).distinct.size == 1)
// Do something.
}
// Compiles and runs.
processArray(RectArray2D(
Sized( 0, 1, 2, 3),
Sized(10, 11, 12, 13),
Sized(20, 21, 22, 23)
))
// Doesn't compile.
processArray(RectArray2D(
Sized( 0, 1, 2, 3),
Sized(10, 11, 12),
Sized(20, 21, 22, 23)
))