我可以转换类型 Expr的℃的报价;'A - > 'B> 来通过下面的代码片段一个LINQ表达式:
I can convert a quotation of type Expr<'a -> 'b> to a Linq expression via the following snippet:
/// Converts a F# Expression to a LINQ Lambda let toLambda (exp:Expr) = let linq = exp.ToLinqExpression() :?> MethodCallExpression linq.Arguments.[0] :?> LambdaExpression /// Converts a Lambda quotation into a Linq Lamba Expression with 1 parameter let ToLinq (exp : Expr<'a -> 'b>) = let lambda = toLambda exp Expression.Lambda<Func<'a, 'b>>(lambda.Body, lambda.Parameters)现在我想转换型报价 Expr的<A *b - > C> 或者甚至 Expr的<'A - > B - > C> 来型的Linq Lambda表达式表达式来; Func键<'一'B'C>>
Now I want to convert a quotation of type Expr<'a * 'b -> 'c> or maybe even Expr<'a -> 'b -> 'c> to a Linq Lambda Expression of type Expression<Func<'a,'b'c>>.
我怎样才能做到这一点?
How can I do this?
问候, forki
Regards, forki
推荐答案我不知道这是直接由F#PowerPack中提供的LINQ模块的支持。但是,您可以实现通过F#库产生的LINQ表达自己的后处理把它变成了一般形式的C#lambda函数:
I'm not sure if this is directly supported by the LINQ modules available in the F# PowerPack. However, you can implement your own post-processing of the LINQ expression produced by F# libraries to turn it into a C# lambda function of the usual form:
下面的函数取其被构造为单个参数的多个嵌套 LambdaExpression 表达式(即,被F#翻译产生的结构),并返回所述内的参数的列表和身体LINQ表达式 - 大多数表达式:
The following function takes a LINQ expression which is constructed as multiple nested LambdaExpression expressions of a single parameter (that is, the structure produced by F# translator) and returns a list of parameters and body of the inner-most expression:
let rec translateExpr (linq:Expression) = match linq with | :? MethodCallExpression as mc -> let le = mc.Arguments.[0] :?> LambdaExpression let args, body = translateExpr le.Body le.Parameters.[0] :: args, body | _ -> [], linq现在你可以用它来获得一个普通的 Func键委托出去的类型,例如 INT - > INT - > INT - > INT 是这样的:
Now you can use it to get an ordinary Func delegate out of type such as int -> int -> int -> int like this:
let linq = (<@@ fun a b c -> (a + b) * c @@>).ToLinqExpression() let args, body = translateExpr liq let f = Expression.Lambda<Func<int, int, int, int>> (body, args |> Array.ofSeq) f.Compile().Invoke(10, 11, 2)更多推荐
转换F#报价为LINQ表达式
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