Graph CE

[vasily-kirichenko]

type GraphBuilder(b: GraphDsl.Builder<_>) =
    member __.Return x = x
    member __.Yield x = x
    member __.Bind(m, f) = f(b.Add(m))

[<AutoOpen>]
module GraphBuilder =
    let graph = GraphBuilder

let partition (evens: Flow<int, 'a, _>) (odds: Flow<int, 'a, _>) =
        Graph.create (fun b -> 
            graph b {
                let! p = Partition(2, fun x -> if x % 2 = 0 then 0 else 1)
                let! merge = Merge<_>(2)
                b.From(p.Out 0).Via(evens).To(merge.In 0)
                b.From(p.Out 1).Via(odds).To(merge.In 1)
                return FlowShape(p.In, merge.Out)
            })

It works, but I don't like how Graph.create (fun b -> graph b { ... }) looks :( Also, I'd like to add custom operations so the following would be possible:

graph b {
    let! p = Partition(2, fun x -> if x % 2 = 0 then 0 else 1)
    let! merge = Merge<_>(2)

    from (p.Out 0)
    via evens
    to (merge.In 0)

    return FlowShape(p.In, merge.Out)
}

(I've failed so far).

[Horusiath]

Great idea :) With custom operations, maybe we'd be able to completely remove builder and keep it implicit inside the computation expression itself. I was thinking about something like:

graph {
    let! p = Partition(2, fun x -> if x % 2 = 0 then 0 else 1)
    let! merge = Merge<_>(2)

    connect (p.Out 0 => evens => merge.In 0)

    return FlowShape(p.In, merge.Out)
}

[vasily-kirichenko]

yes, I thought about hiding the builder, but I cannot see how to obtain one inside the CE since it does not have public ctor and the only way to get it is inside lambda passed to Graph.create.