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Using Poly/ML, I wanted to write a function to construct an n*n identity matrix using Array of Arrays.

I wrote:

fun equiv x y = if x = y then 1 else 0;
fun idmatrix n = Array.tabulate(n, fn i => (Array.tabulate(n, equiv i)));

and it compiled successfully, giving

> val equiv = fn: ''a -> ''a -> int
> val idmatrix = fn: int -> int array array

But when I called idmatrix

idmatrix 2;

for a test, the output of the compiler was

> Exception- Cast "toAddress" raised

Can anybody explain why the exception was raised, please?

Thank you very much!

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1 回答 1

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你的代码对我来说很好。查看引发异常的代码，可能是 32/64 位地址问题？您的 Poly/ML 是否针对正确的架构进行编译？

聚/毫升：

$ poly
Poly/ML 5.2 Release
> fun equiv x y = if x = y then 1 else 0;
val equiv = fn : ''a -> ''a -> int
> fun idmatrix n = Array.tabulate(n, fn i => (Array.tabulate(n, equiv i)));
val idmatrix = fn : int -> int Array.array Array.array
> idmatrix 3;
val it = fromList[fromList[1, 0, 0], fromList[0, 1, 0], fromList[0, 0, 1]]
: int Array.array Array.array

莫斯科毫升：

$ mosml
Moscow ML version 2.10
Enter `quit();' to quit.
- fun equiv x y = if x = y then 1 else 0;
> val ''a equiv = fn : ''a -> ''a -> int
- fun idmatrix n = Array.tabulate(n, fn i => (Array.tabulate(n, equiv i)));
> val idmatrix = fn : int -> int array array
- idmatrix 3;
> val it = <array> : int array array

和 SML/NJ：

$ sml
Standard ML of New Jersey v110.76 [built: Sun Jun 29 03:29:51 2014]
- fun equiv x y = if x = y then 1 else 0;
stdIn:1.23 Warning: calling polyEqual
val equiv = fn : ''a -> ''a -> int
- fun idmatrix n = Array.tabulate(n, fn i => (Array.tabulate(n, equiv i)));
[autoloading]
[library $SMLNJ-BASIS/basis.cm is stable]
[autoloading done]
val idmatrix = fn : int -> int array array
- idmatrix 3;
val it = [|[|1,0,0|],[|0,1,0|],[|0,0,1|]|] : int array array
于 2018-01-08T18:24:47.153 回答