Reader.fs

namespace Fable.Remoting.Server 

type Reader<'a, 'b> = Reader of ('a -> 'b) 

module Reader = 
  let run a (Reader fromAtoB) = 
    let b = fromAtoB a 
    b

  let returnM b = Reader (fun _ -> b) 
  
  let bindM f reader = 
      let nextReader environment =
          let x = run environment reader 
          run environment (f x)
      Reader nextReader

type ReaderBuilder<'t, 'u>() = 
  member this.Return(x) = Reader.returnM x 
  member this.Bind(x, f) = Reader.bindM f x