Bdtjtk

Here is a simplified snippet of the Provided method which accepts variable number of arguments, in this case 3

ProvidedMethod(methodName = "GetContext", 

               parameters = [ for i in [ 1..3 ] do

                                  yield ProvidedParameter("Param" + string i, typeof<string>) ], 

               IsStaticMethod = true, returnType = typeof<string>, 

               InvokeCode = (fun args -> 

                   <@@ 

                       let dim1 : string = %%args.[0] : string

                       let dim2 : string = %%args.[1] : string

                       let dim3 : string = %%args.[2] : string

                 //    let dims = [for %%arg in args do yield (arg : string) ]// [1] error below

                 //    let dims = [for arg in args do yield (%%arg : string) ]// [2] error below

                       let dims = [ dim1; dim2; dim3 ] //this works

                       String.Join("--", dims)

                   @@>))

I want to collect all arguments in a single list.

What I've tried and did not work is commented in code quotation.

[1]: [FS0010] Unexpected prefix operator in expression

     [FS0594] Identifier expected



[2]: [FS0446] The variable 'arg' is bound in a quotation but is used as part of a spliced expression. This is not permitted since it may escape its scope.

Hacking your solution in the following way actually compiles

InvokeCode = (fun args -> 

    let dims: string = Array.zeroCreate args.Length

    let mutable i = 0

    let inc () = i <- i + 1

    <@@

        while i < args.Length do

            dims.[i] <- %%args.[i]

            inc ()

        String.Join("--", dims)

    @@>

But I suspect that you rather want to transform a Quotations.Expr of the shape [|Value ("a"); Value ("b"); Value ("c")|] into a single Quotations.Expr.

You can use the patterns in Microsoft.FSharp.Quotations.Patterns to extract stuff from the expressions in the following way

InvokeCode = (fun args -> 

    let dims =

        args

        |> Array.choose (function | Value(value, _) -> value |> string |> Some | _ -> None)

        |> fun arr -> String.Join("--", arr)

    <@@ dims @@>

This kind of solution also worked based on the answer suggested in comments: F# Type Provider development: When providing a method, how to access parameters of variable number and type?

ProvidedMethod(methodName = "GetContext", 

           parameters = [ for i in [ 1..3 ] do

                              yield ProvidedParameter("Param" + string i, typeof<string>) ], 

           IsStaticMethod = true, returnType = typeof<string>, 

           InvokeCode = (fun args -> 

               let dims = List.fold ( fun state e -> <@@ (%%string)::%%state @@>) <@@ :List<string> @@> args

               <@@ 

                   String.Join("--", dims)

               @@>))