Question

我是F＃的新手，我正在尝试编写一个计算powerset的函数。

我从Mono（在Mac上运行它）收到错误。

例如，我将通过calcPowerSet（[1; 2; 3]，[]）来启动该函数。关于如何解决这个问题的任何想法？

System.InvalidProgramException: Invalid IL code in FSI_0010:calcPowerSet (Microsoft.FSharp.Collections.List`1,Microsoft.FSharp.Collections.List`1): IL_005d: stind.r4  


  at FSI_0010.calcPowerSet[Int32] (Microsoft.FSharp.Collections.List`1 _arg1_0, Microsoft.FSharp.Collections.List`1 _arg1_1) [0x00000] 
  at .$FSI_0011._main () [0x00000] 
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[],System.Exception&)
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] 
stopped due to error

代码：

let rec calcPowerSet = function
 | ([], []) -> [[]]
 | ((head::tail), (cHead::cTail)) -> 
  calcPowerSet (tail, (cHead::cTail)) @ calcPowerSet (tail, (head::cHead::cTail))
 | ((head::tail), []) -> 
  calcPowerSet (tail, []) @ calcPowerSet (tail, [head])
 | ([], collect) -> [collect];;

Answer 1

我不知道它为什么不起作用（我得到了相同的结果），但如果你把它重写为：

let calcPowerSet =
   let rec innerCalc = 
      function
      | ([], []) -> [[]]
      | ((head::tail), (cHead::cTail)) -> 
         innerCalc (tail, (cHead::cTail)) @ innerCalc (tail, (head::cHead::cTail))
      | ((head::tail), []) -> 
         innerCalc (tail, []) @ innerCalc (tail, [head])
      | ([], collect) -> [collect]
   innerCalc

它似乎在Mac（英特尔）下使用Mono 2.4和F＃1.9.6.2

工作正常

Answer 2

仅供参考，事实证明F＃团队已经意识到这个错误，这是Mono团队所知道的Mono 2.4中的一个错误（dunno，如果已经修复）。

无效的IL代码 - F＃

2 个答案: