Overview

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The library Fmlib_browser helps to write web applications which run in the browser in a pure functional style. It mimics the elm language in ocaml.

The core of a functional web application is a system state and 2 main functions to describe the behaviour of a web application.

1. The system state: It contains all relevant data of the application. For a pure static page with no interaction with the user the state is just the unit value (). For an application representing a counter which can be increased or decreased by clicking on buttons the state is an int which represents the value of the counter.
2. A view function: This function maps the state into a virtual dom. The virtual dom is a description of what the user sees on the screen. Furthermore the virtual dom contains elements like buttons or text fields which produce messages. The messages are dispatched to the update function.
3. An update function: The update function maps the state of the application and a message to a new state.

If we just want to display a static page with a grocery list the functions are quite simple.

    type message    (* no constructor, i.e. no message can be created. *)

    let view (): unit Html.t =
        let open Html in
        ol [] [
            text "Milk";
            text "Honey";
            text "Meet"
        ]

    let update () (_: message): unit =
        assert false (* Function can never be called because [message] has no
                        constructor *)

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