`type..with` Construct

[SpiralOSS]

Need type... with and possible links from Code Organization

[IanWitham]

My main use case for type ... with is in taking module functions that I intend to use from C# and making them appear as methods on a type. e.g.

type Animal = { Species: string; Noise: string }

module Animal =
    let speak (animal : Animal) = printfn $"{animal.Noise}! says the {animal.Species}"

{ Species = "pig"; Noise = "oink" } |> Animal.speak // idiomatic F#

type Animal with
    member this.speak() = Animal.speak this

{ Species = "dog"; Noise = "woof" }.speak()         // better for C#

This also shows the pattern of having a type and it's accompanying module use the same name. (too confusing for beginners?)

[bartelink]

I use type with to layer OO dottable extensions onto e.g. a type Sut that I have in an acceptance test suite...
Any file that's got a top level module with AutoOpen can feed extensions in on top that are usable further down the compile order. Not sure if that makes for a good example or whether its best to stick with the animals; probably the latter....