基本上,我想要一个函数来从一个节点和 2 个子堆中创建一个堆。堆表示如下(其中Cons中的int表示节点的rank)
datatype 'a heap = Empty | Heap of int * 'a * 'a heap * 'a heap
我的功能是:
fun makeHeap x h1 h2 = Heap ((rank h1)+1, x, h1, h2)
程序编译但当我调用 makeHeap 时,我得到一个奇怪的值而不是堆:
makeHeap(#"c", Empty, Empty);
stdIn:72.1-72.29 Warning: type vars not generalized because of
value restriction are instantiated to dummy types (X1,X2,...)
val it = fn
: (char * ?.X1 heap * ?.X2 heap) heap
-> (char * ?.X1 heap * ?.X2 heap) heap
-> (char * ?.X1 heap * ?.X2 heap) heap