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Higher-order functions

Several higher-order functions are available on containers, for example foreach, count, exists, forall, foldLeft (or /:); however, the calling convention is slightly different from the Scala collections to avoid allocating tuples:

import metal._; import syntax._
val m = mutable.HashMap(1 -> 2, 3 -> 4)

scala> m.foreach { (k, v) => println(s"($k, $v)") }
(1, 2)
(3, 4)

instead of

m.foreach { case (k, v) => println(s"($k, $v)") }

The methods min, max, sum, product are also available; the required algebraic operations (orders, additive monoids, multiplicative monoids) are provided using Spire type classes. Contrary to the standard Scala library, Spire is heavily specialized on primitive types.

Those higher-order functions are implemented using implicit classes and macros, to avoid polluting the container interfaces.

At compilation time, a call such as m.foreach { (k, v) => println(k) } is inlined, producing code similar to:

@inline def rec(ptr: Ptr[m.Tag, m.Cap]): Unit = ptr match {
    case IsVPtr(vp) =>
      val k = m.ptrKey[Int](vp)
      val v = m.ptrValue[Int](vp)
      println(k)
      rec(m.ptrNext(vp))
    case _ =>
  }