我写了一个函数,该函数将数组作为输入,并返回一个相等大小的数组与输出相等的数组。例如:
myFunc [| "apple"; "orange"; "banana" |]
> val it : (string * string) [] =
[|("red", "sphere"); ("orange", "sphere"); ("yellow", "oblong")|]
现在,我想通过绑定来分配结果。例如:
let [|
( appleColor, appleShape );
( orangeColor, orangeShape );
( bananaColor, bananaShape )
|] =
myFunc [| "apple"; "orange"; "banana" |]
效果很好...
> val orangeShape : string = "sphere"
> val orangeColor : string = "orange"
> val bananaShape : string = "oblong"
> val bananaColor : string = "yellow"
> val appleShape : string = "sphere"
> val appleColor : string = "red"
...除了发出警告外:
warning FS0025: Incomplete pattern matches on this expression. For example, the value '[|_; _; _; _|]' may indicate a case not covered by the pattern(s).
警告的来源和原因已经涵盖,我只是在寻找简洁的工作。此功能调用发生在我功能的顶部附近,我不喜欢将整个功能物体放入比赛中的想法:
let otherFunc =
match myFunc [| "apple"; "orange"; "banana" |] with
| [|
( appleColor, appleShape );
( orangeColor, orangeShape );
( bananaColor, bananaShape )
|] ->
// ... the rest of my function logic
| _ -> failwith "Something impossible just happened!"
闻起来很臭。我不喜欢忽略警告的想法 - 反对我更好的判断。还有其他选择对我开放,还是我只需要完全找到其他方法?
如果您期望这种呼叫模式经常使用,那就是制作包装器,以对您期望的元组进行作用,例如
myFunc3 (in1,in2,in3) =
match myFunc [|in1;in2;in3|] with
[|out1;out2;out3|] -> out1, out2, out3
_ -> failwith "Internal error"
等。但是它所做的就是将丑陋的代码移至标准位置,并且写出包装纸会带来不便。
我认为此API没有更好的选择,因为没有办法告诉编译器myFunc
总是返回通过它传递的相同数量的元素。
另一个选项可能是用IDisposable
类替换myFunc
:
type MyClass() =
let expensiveResource = ...
member this.MyFunc(v) = ...calculate something with v using expensiveResource
interface IDisposable with
override this.Dispose() = // cleanup resource
然后将其在
之类的块中使用use myClass = new MyClass()
let appleColor, appleShape = myClass.MyFunc(apple)
...
适应 @ganesh的答案,这是解决问题的原始方法:
let Tuple2Map f (u, v)
= (f u, f v)
let Tuple3Map f (u, v, w)
= (f u, f v, f w)
let Tuple4Map f (u, v, w, x)
= (f u, f v, f w, f x)
示例:
let Square x = x * x
let (a,b) = Tuple2Map Square (4,6)
// Output:
// val b : int = 36
// val a : int = 16
,但我猜是这样的更原始的是:
let Square x = x * x
let (a,b) = (Square 4, Square 6)
,如果函数名称太长,例如
// Really wordy way to assign to (a,b)
let FunctionWithLotsOfInput w x y z = w * x * y * z
let (a,b) =
(FunctionWithLotsOfInput input1 input2 input3 input4A,
FunctionWithLotsOfInput input1 input2 input3 input4B)
我们可以定义临时函数
let FunctionWithLotsOfInput w x y z = w * x * y * z
// Partially applied function, temporary function
let (a,b) =
let f = (FunctionWithLotsOfInput input1 input2 input3)
(f input4A, f input4B)