I have a lambda join in C# which looks like this:
我在C#中有一个lambda连接,看起来像这样:
int[] arrX = { 1, 2, 3 };
int[] arrY = { 3, 4, 5 };
var res = arrX.Join(arrY, x => x, y => y, (x, y) => x);
After execution res contains 3 which is common for both arrays.
执行后res包含3,这对两个数组都是通用的。
I want to make the exact same lambda join in F#, and try:
我想在F#中进行完全相同的lambda连接,并尝试:
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
let res = arrX.Join(fun arrY, fun x -> x, fun y -> y, fun (x, y) -> x)
But the compiler says:
但是编译器说:
Unexpected symbol ',' in lambda expression. Expected '->' or other token.
lambda表达式中的意外符号','。预期' - >'或其他令牌。
The error is the comma after the first parameter arrY.
错误是第一个参数arrY后面的逗号。
Can you tell me how I can get it to work (as a lambda expression)?
你能告诉我如何让它工作(作为一个lambda表达式)?
3 个解决方案
#1
3
this will work for me in F#-interactive (and is the direct translation from your C# code):
这对我来说在F#-interactive中起作用(并且是从你的C#代码直接翻译):
open System
open System.Linq
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
let res = arrX.Join(arrY, Func<_,_>(id), Func<_,_>(id), (fun x _ -> x))
after executing res
will look like this:
执行res后会看起来像这样:
> res;;
val it : Collections.Generic.IEnumerable<int> = seq [3]
remarks
if you like you can write
如果你愿意,你可以写
let res = arrX.Join(arrY, (fun x -> x), (fun x -> x), fun x _ -> x)
as @RCH proposed too
正如@RCH提出的那样
#2
1
Note that there are at least two ways to do this using the F# core lib.
请注意,使用F#核心库至少有两种方法可以实现此目的。
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
//method 1 (does not preserve order)
let res1 = Set.intersect (set arrX) (set arrY)
//method 2
let res2 =
query {
for x in arrX do
join y in arrY on (x = y)
select x
}
#3
0
May I boldly suggest the following:
我可以大胆地提出以下建议:
open System
open System.Linq
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
let res = Set.intersect (Set.ofArray arrX) (Set.ofArray arrY) |> Set.toArray
or if going for some total "obfuscation style":
或者如果要采取一些完整的“混淆风格”:
let res' = arrX |> Set.ofArray |> Set.intersect <| (Set.ofArray <| arrY) |> Set.toArray
I guess the res'-version is not recommended...
我想不建议使用res'版本......
:-)
:-)
#1
3
this will work for me in F#-interactive (and is the direct translation from your C# code):
这对我来说在F#-interactive中起作用(并且是从你的C#代码直接翻译):
open System
open System.Linq
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
let res = arrX.Join(arrY, Func<_,_>(id), Func<_,_>(id), (fun x _ -> x))
after executing res
will look like this:
执行res后会看起来像这样:
> res;;
val it : Collections.Generic.IEnumerable<int> = seq [3]
remarks
if you like you can write
如果你愿意,你可以写
let res = arrX.Join(arrY, (fun x -> x), (fun x -> x), fun x _ -> x)
as @RCH proposed too
正如@RCH提出的那样
#2
1
Note that there are at least two ways to do this using the F# core lib.
请注意,使用F#核心库至少有两种方法可以实现此目的。
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
//method 1 (does not preserve order)
let res1 = Set.intersect (set arrX) (set arrY)
//method 2
let res2 =
query {
for x in arrX do
join y in arrY on (x = y)
select x
}
#3
0
May I boldly suggest the following:
我可以大胆地提出以下建议:
open System
open System.Linq
let arrX = [| 1; 2; 3 |]
let arrY = [| 3; 4; 5 |]
let res = Set.intersect (Set.ofArray arrX) (Set.ofArray arrY) |> Set.toArray
or if going for some total "obfuscation style":
或者如果要采取一些完整的“混淆风格”:
let res' = arrX |> Set.ofArray |> Set.intersect <| (Set.ofArray <| arrY) |> Set.toArray
I guess the res'-version is not recommended...
我想不建议使用res'版本......
:-)
:-)