我正在尝试使用各种 Scala 实现的类似 C# 的 yield return (即这个)和 "for" -constructions,例如:
private def permutations[T](s: Vector[T]) = {
def swap(i: Int, j: Int) {
val tmp = s(i)
s.set(i, s.get(j))
s.set(j, tmp)
}
iterator[Vector[T]] {
def generate(left: Int, right: Int): Unit @cps[Iteration[Vector[T]]] = {
if (left >= right)
yieldValue(s)
else {
generate(left, right)
for (i <- left to right) {
swap(left, i)
generate(left+1, right)
swap(left, i)
}
}
}
generate(0, s.size-1)
}
}
但是这段代码编译错误:
error: no type parameters for method foreach: (f: (Int) => U)Unit exist so that it can be applied to arguments ((Int) => Unit @util.continuations.package.cps[ru.ispras.texterra.nlp.GHMMDisambiguator.Iteration[Vector[T]]])
--- because ---
argument expression's type is not compatible with formal parameter type;
found : (Int) => Unit @util.continuations.package.cps[ru.ispras.texterra.nlp.GHMMDisambiguator.Iteration[Vector[T]]]
required: (Int) => ?U
for (i <- left to right) {
据我了解,我必须将所有代码都设置为类型() => Unit
,而不是类型() => Unit @with-annotations
。我怎样才能做到这一点?
这个问题似乎很常见,但是我在网上没有找到任何提及。