在scala,为什么';下限在这里不起作用吗?
这些代码编译得很好:在scala,为什么';下限在这里不起作用吗?,scala,generics,types,functional-programming,type-inference,Scala,Generics,Types,Functional Programming,Type Inference,这些代码编译得很好: abstract class CodeTree case class Fork(left: CodeTree, right: CodeTree, chars: List[Char], weight: Int) extends CodeTree case class Leaf(char: Char, weight: Int) extends CodeTree def weight(tree: CodeTree): Int = tree match {
abstract class CodeTree
case class Fork(left: CodeTree, right: CodeTree, chars: List[Char], weight: Int) extends CodeTree
case class Leaf(char: Char, weight: Int) extends CodeTree
def weight(tree: CodeTree): Int = tree match {
case Fork(left, right, chars, weight) => weight
case Leaf(char, weight) => weight
}
def insert_orderedCodeTreeList[T >: CodeTree](leaf: CodeTree, orderedCodeTrees: List[CodeTree]): List[T] = orderedCodeTrees match {
case Nil => List(leaf)
case head :: tail => {
if (weight(leaf) <= weight(head)) leaf :: orderedCodeTrees
else head :: insert_orderedCodeTreeList(leaf, tail)
}
}
可以看出,类型参数T
使用CodeTree
作为下限,因此,我认为在insert\u orderedCodeTreeList
的参数列表中,可以将CodeTree替换为T
:
def insert_orderedCodeTreeList[T >: CodeTree](leaf: T, orderedCodeTrees: List[T]): List[T] = orderedCodeTrees match {
case Nil => List(leaf)
case head :: tail => {
if (weight(leaf) <= weight(head)) leaf :: orderedCodeTrees
else head :: insert_orderedCodeTreeList(leaf, tail)
}
}
def insert\u orderedCodeTreeList[T>:CodeTree](叶:T,orderedCodeTrees:List[T]):List[T]=orderedCodeTrees匹配{
案例Nil=>列表(叶)
案例头部::尾部=>{
如果(重量(叶子)阅读后,我发现正确的方法是这样写:
insert_orderedCodeTreeList[Leaf](Leaf(theChar, theInt), makeOrderedLeafList(tail))
type arguments [patmat.Huffman.Leaf] do not conform to method insert_orderedCodeTreeList's type parameter bounds [T >: patmat.Huffman.CodeTree]
[error] case (theChar, theInt) :: tail => insert_orderedCodeTreeList[Leaf](Leaf(theChar, theInt), makeOrderedLeafList(tail))
[error] ^
[error] one error found
def insert_orderedCodeTreeList[T <: CodeTree](leaf: T, orderedCodeTrees: List[T]): List[T] = orderedCodeTrees match {
case Nil => List(leaf)
case head :: tail => {
if (weight(leaf) <= weight(head)) leaf :: orderedCodeTrees
else head :: insert_orderedCodeTreeList(leaf, tail)
}
}
def insert_orderedCodeTreeList[T列表(叶)
案例头部::尾部=>{
if(叶重)
def insert_orderedCodeTreeList[T <: CodeTree](leaf: T, orderedCodeTrees: List[T]): List[T] = orderedCodeTrees match {
case Nil => List(leaf)
case head :: tail => {
if (weight(leaf) <= weight(head)) leaf :: orderedCodeTrees
else head :: insert_orderedCodeTreeList(leaf, tail)
}
}