Reinventing the Reader Monad

/// Applies the specified function to all items in the list.
/// If any of the function calls results in a Failure, the
/// map function returns failure immediately.
let mapOrFail f items = 
    let rec loop acc items =
        match items with
        | x::xs -> 
            match f x with
            | Success r -> loop (r::acc) xs
            | fail -> fail
        | [] -> Success(List.rev acc)
    loop [] items


let getPurchaseInfo (custId:CustId)  : Result<ProductInfo list> =

    // Open api connection (I'm not calling 'Close' at the end
    // because this is should be done done automatically, as the
    // client implements IDisposable)
    use api = new ApiClient()
    api.Open()

    // Get product ids purchased by customer id
    let productIdsResult = api.Get<ProductId list> custId
    match productIdsResult with
    | Success productIds -> 
        productIds |> mapOrFail (api.Get<ProductInfo>)
    | Failure err -> 
        Failure err