假设我有两个SML函数Ping和Pong.My代码是这样的:
val arr=Array.array(10,0)
fun Ping (arr,_,[],_)=true
|Ping (arr,0,(x::xs),ping_list)=Ping(arr,1,xs,Pong(arr,ping_list,10)) //<-Problem is here
| Ping (arr,K,(x :: xs),ping_list) =
(if Array.sub(arr,x)=0
then
Array.update(arr, x, Array.sub(arr,x)+1)
else
Array.update(arr, x, Array.sub(arr,x)+1);
if Array.sub(arr,x)-1<1 then Ping (arr,(K-1),xs,(x::ping_list)) else Ping (arr,K,xs,(x::ping_list)))
fun Pong arr [] _ =[]
|Pong arr (x::xs) min=
(if Array.sub(arr,x)>=1
then Array.update(arr,x,Array.sub(arr,x)-1)
else();
if Array.sub(arr,x)+1>1
then if (length xs)<min then Pong arr xs (length xs)
else Pong arr xs min
else xs)
如果我调用Ping,让我们说一个数组,3:int,[1,2,3]:list,[]它给了我令人厌恶的输出。以同样的方式,如果我用一个数组调用Pong,列表,整数给出我想要的输出。在ping函数中,如果K = 0,我想调用pong函数(修改数组)并递归调用Ping函数但在参数ping_list中有Pong的结果(这是一个列表)但是运行thisgives我这个错误:
stdIn:27.40-27.73 Error: operator and operand do not agree [tycon mismatch]
operator domain: int array
operand: 'Z * 'Y * [int ty]
in expression:
Pong (arr,ping_list,10)
我也尝试将Ping和Pong放在本地并从中调用Ping,但它似乎没有用。如何解决这个问题?
Control.Print.printDepth := 20;
val arr = Array.array(10,0)
fun Ping (arr, _, [], _) = true
|Ping (arr, 0, (x::xs), ping_list) = Ping(arr, 1, xs, Pong(arr, ping_list, 10))
|Ping (arr, K, (x :: xs), ping_list) =
(if Array.sub(arr, x) = 0
then Array.update(arr, x, Array.sub(arr, x)+1)
else Array.update(arr, x, Array.sub(arr, x)+1);
if Array.sub(arr, x)-1 < 1
then Ping(arr, (K-1), xs, (x::ping_list))
else Ping(arr, K, xs, (x::ping_list)))
and Pong(arr, [], _) = []
|Pong(arr, (x::xs), min) =
(if Array.sub(arr, x) >= 1
then (Array.update(arr, x, Array.sub(arr, x)-1); [])
else [];
if Array.sub(arr,x) + 1 > 1
then if (length xs) < min then Pong(arr, xs, (length xs)) else Pong(arr, xs, min)
else xs);
val result = Ping(arr, 3, [0, 2, 4], []);
val it = arr;
输出:
val arr = [|0,0,0,0,0,0,0,0,0,0|] : int array
val Ping = fn : int array * int * int list * int list -> bool
val Pong = fn : int array * int list * int -> int list
val result = true : bool
val it = [|1,0,1,0,1,0,0,0,0,0|] : int array
我在运行之前修复的问题:
()
和int list
)