Extending Core.Option module in F# -


i want extend 1 of existing "core" modules, core.option:

module microsoft.fsharp.core.option      let filter predicate op =         match op         | some(v) -> if predicate(v) some(v) else none         | none -> none

(i know bind function, think filter method options in case more convenient).

but unfortunetely can't use filter method without explicitely open microsoft.fsharp.core namespace:

// commenting following line break code! open microsoft.fsharp.core  let v1 = 42 let v2 = v1 |> option.filter (fun v -> v > 40)  printfn "v2 is: %a" v2

in cases can't use functions module without opening appropriate namespace. f# compiler "opens" predefine (core) namespace automatically (like microsoft.fsharp.core), not bring scope methods "module extensions" , still should open core namespaces manually.

my question is: there workarounds?

or best way extend "core" modules create such extensions in custom namespace , open namespace manually?

// lets custom option module in our custom namespace module customnamespace.option      let filter predicate op = ...  // on client side lets open our custom namespace. // after can use both option modules simultaneously! open customnamespace  let v1 = 42 let b =      v1 |> option.filter (fun v -> v > 40) // using customnamespace.option     |> option.issome // using microsoft.fsharp.core.option

does if add autoopen attribute module?

[<autoopen>] module microsoft.fsharp.core.option      let filter predicate op =         match op         | some(v) -> if predicate(v) some(v) else none         | none -> none

edit

this works, across assembly borders. doesn't work within same assembly:

namespace microsoft.fsharp.core module option =     let filter predicate op =         match op         | some(v) -> if predicate(v) some(v) else none         | none -> none  [<assembly:autoopen("microsoft.fsharp.core")>] ()

to call assembly:

[<entrypoint>] let main args =      let f () = "" |> option.filter (fun f -> true)     console.writeline("hello world!")     0

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