F#中的功能模板 [英] Function templates in F#
问题描述
假设我正在解决一个特定的问题并提出一个功能
Let's say I am solving a particular problem and come up with a function
let function parameter1 ... =
a lot of adding, multiplying & so on with a lot of
literals all over the place
现在,如果我的参数为int类型,则此功能正常运行.但是在某个地方,我需要将其提高到11,我需要额外地将其推入int64甚至BigInteger.那我该怎么办? 我复制并粘贴该函数,更改名称,然后搜寻所有使编译器认为该函数应在int上运行的文字外观.这很烂.
Now this function works fine if my parameters are of type int. But somewhere I will need it to go up to 11, I will need that extra push into int64 or even BigInteger. So what do I do? I copy&paste the function, change the name, and go hunting for all literal appearances that make the compiler think the function should operate on int. And this sucks.
有没有办法做到这一点:
Is there a way to do this:
let greatFunction param1 param2 = (param1+1)/(param2*2)
其中param1和param2可以是整数类型的任意组合吗?
where param1 and param2 can be any combo of integer types?
下面通过kvb扩展了一个很好的技巧,我想到了以下内容
Expanding a bit on a great tip by kvb below, I came up with the following
module NumericLiteralG
let inline FromZero() = LanguagePrimitives.GenericZero
let inline FromOne() = LanguagePrimitives.GenericOne
let inline FromInt32 n =
let rec loop nIn nOut =
if nIn>0 then loop (nIn - 1) (nOut + LanguagePrimitives.GenericOne)
else nOut
loop n LanguagePrimitives.GenericZero
因此使用起来会变得不那么难看
so it becomes a bit less ugly when used
let inline halfSquare num =
let res = num / 2G
res * res
let solve1 = halfSquare 5I
let solve2 = halfSquare 5.0
let solve3 = halfSquare 5uy
现在的问题是我应该使用这个吗?如果没有,为什么不呢?
Now the question is should I use this? If not, why not?
推荐答案
我认为通用算术是.NET语言中的常见问题. 有很多文章介绍了不同的方法,不久我将发布另一篇文章来解释我的方法,与您发布的解决方案相似.
I think Generic Arithmetic is common problem in .NET languages. There are many articles explaining different approaches and very soon I will post another one explaining mine which is similar to the solution you posted.
现在,如果您问我是否应该使用它,我会说:只要您了解自己在做什么,为什么不呢?我在生产中使用了它的一部分,没有任何问题,但是因为我关心运行时性能,所以我使用重载来解决编译时的所有问题. 然后,为了加快编译时间,我重新定义了基本数学运算符以使用相同的类型,否则类型签名会变得非常复杂,并且可能需要很长时间才能编译.
Now, if you ask me if should you use it, I would say: as long as you understand what you are doing why not? I'm using it partially in production and have no issues at all, but because I care about run-time performance I use overloading to resolve everything at compile time. Then to speed up compile time I redefine basic math operators to operate in the same type, otherwise type signatures get really complicated and may take ages to compile.
还有更多要考虑的事情,但是对于您的特定问题,这里是示例代码:
There are more things to consider but for your specific problem here is a sample code:
open System.Numerics
type FromInt = FromInt with
static member ($) (FromInt, _:sbyte ) = fun (x:int) -> sbyte x
static member ($) (FromInt, _:int16 ) = fun (x:int) -> int16 x
static member ($) (FromInt, _:int32 ) = id
static member ($) (FromInt, _:float ) = fun (x:int) -> float x
static member ($) (FromInt, _:float32 ) = fun (x:int) -> float32 x
static member ($) (FromInt, _:int64 ) = fun (x:int) -> int64 x
static member ($) (FromInt, _:nativeint ) = fun (x:int) -> nativeint x
static member ($) (FromInt, _:byte ) = fun (x:int) -> byte x
static member ($) (FromInt, _:uint16 ) = fun (x:int) -> uint16 x
static member ($) (FromInt, _:char ) = fun (x:int) -> char x
static member ($) (FromInt, _:uint32 ) = fun (x:int) -> uint32 x
static member ($) (FromInt, _:uint64 ) = fun (x:int) -> uint64 x
static member ($) (FromInt, _:unativeint) = fun (x:int) -> unativeint x
static member ($) (FromInt, _:bigint ) = fun (x:int) -> bigint x
static member ($) (FromInt, _:decimal ) = fun (x:int) -> decimal x
static member ($) (FromInt, _:Complex ) = fun (x:int) -> Complex(float x,0.0)
let inline fromInt (a:int) : ^t = (FromInt $ Unchecked.defaultof< ^t>) a
module NumericLiteralG =
let inline FromZero() =LanguagePrimitives.GenericZero
let inline FromOne() = LanguagePrimitives.GenericOne
let inline FromInt32 (i:int) = fromInt i
// This will reduce the number of types inferred, will reduce compile time too.
let inline (+) (a:^t) (b:^t) : ^t = a + b
let inline (-) (a:^t) (b:^t) : ^t = a - b
let inline (*) (a:^t) (b:^t) : ^t = a * b
let inline (/) (a:^t) (b:^t) : ^t = a / b
let inline (~-) (a:^t) : ^t = -a
let inline halfSquare num =
let res = num / 2G
res * res
let solve1 = halfSquare 5I
let solve2 = halfSquare 5.0
let solve3 = halfSquare 5uy
// Define more generic math functions.
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