如果您有一个依赖于其他函数的递归函数,实现它的首选方法是什么?
1( 递归函数之外
let doSomething n = ...
let rec doSomethingElse x =
match x with
| yourDone -> ...
| yourNotDone -> doSomethingElse (doSomething x)
2( 在递归函数内部
let rec doSomethingElse x =
let doSomething n = ...
match x with
| yourDone -> ...
| yourNotDone -> doSomethingElse (doSomething x)
3( 将两者封装在第三个功能中
let doSomethingElse x =
let doSomething n = ...
let innerDoSomethingElse =
match x with
| yourDone -> ...
| yourNotDone -> innerDoSomethingElse (doSomething x)
4( 有更好的东西吗?
module Test =
let f x =
let add a b = a + b //inner function
add x 1
let f2 x =
let add a = a + x //inner function with capture, i.e., closure
add x
let outerAdd a b = a + b
let f3 x =
outerAdd x 1
翻译为:
[CompilationMapping(SourceConstructFlags.Module)]
public static class Test {
public static int f(int x) {
FSharpFunc<int, FSharpFunc<int, int>> add = new add@4();
return FSharpFunc<int, int>.InvokeFast<int>(add, x, 1);
}
public static int f2(int x) {
FSharpFunc<int, int> add = new add@8-1(x);
return add.Invoke(x);
}
public static int f3(int x) {
return outerAdd(x, 1);
}
[CompilationArgumentCounts(new int[] { 1, 1 })]
public static int outerAdd(int a, int b) {
return (a + b);
}
[Serializable]
internal class add@4 : OptimizedClosures.FSharpFunc<int, int, int> {
internal add@4() { }
public override int Invoke(int a, int b) {
return (a + b);
}
}
[Serializable]
internal class add@8-1 : FSharpFunc<int, int> {
public int x;
internal add@8-1(int x) {
this.x = x;
}
public override int Invoke(int a) {
return (a + this.x);
}
}
}
内部函数的唯一额外成本是新建一个FSharpFunc
实例——似乎可以忽略不计。
除非您对性能非常敏感,否则我会选择最有意义的范围,即尽可能窄的范围。