Types 在SML数据类型中处理匿名函数

我有以下数据类型和3个测试示例：

datatype 'a test = Test of ('a -> bool) * string;
val pos = Test (fn x => x > 0, "pos");
val even = Test (fn x => x mod 2 = 0, "even");
val small = Test (fn x => x < 100, "small");

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我假设您希望筛选给定输入通过的测试名称

您可以通过模式匹配分解测试，获得相应的函数并在当前输入上测试它们：

fun pass x [] = []
  | pass x (Test(f, s)::t) = if f x then s::pass x t 
                             else pass x t

fun pass x [] = []
  | pass x (Test(f, s)::t) = if f x then s::pass x t 
                             else pass x t