结构内部的签名
我想将签名/结构对放置在结构内部，如下所示：
structure Outer :> OUTER =
struct
signature INNER =
sig
...
end
structure Inner :> INNER =
struct
...
end
end
但即使是最简单的示例也会产生错误：
../test.sml:1.18-2.6 Error: syntax error: replacing STRUCT with EQUALOP ../test.sml:5.6 Error: syntax error found at END
看来结构内部不允许签名。实现此功能的最佳方法是什么？
I want to place signature/structure pair inside a structure, like so:
structure Outer :> OUTER =
struct
signature INNER =
sig
...
end
structure Inner :> INNER =
struct
...
end
end
but even the simplest of examples produces an error:
../test.sml:1.18-2.6 Error: syntax error: replacing STRUCT with EQUALOP ../test.sml:5.6 Error: syntax error found at END
It appears that signatures are not allowed inside structures. What is the best way to achieve this functionality?
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尽管结构嵌套在 SML 中，但签名却不然。目前尚不清楚您想要实现什么功能：
隐藏命名签名是不可能的。
使
INNER签名依赖于结构Outer中声明的类型是通过fibration实现的（where type条款）。在 Benjamin Pierce 的关于编程语言高级类型的书中，Harper 和 Pierce 的教程中有一个关于纤维化的详细部分。Although structures nest in SML, signatures do not. It's not clear what functionality you want to achieve:
Hiding a named signature is impossible.
Having the
INNERsignature depend on types declared in structureOuteris achieved through fibration (thewhere typeclause). There's a length section on fibration in the tutorial by Harper and Pierce in Benjamin Pierce's book on advanced types in programming languages.您还可以内联内部签名，如
You could also inline the inner signature, as in