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Currently, editors in an invalid state within a Maybe editor are valid and produce a Nothing value. The concept of editors should be changed to include three possible states:

• valid state (e.g. an integer field with "3")
• invalid state (e.g. an integer field with "a")
• empty state (e.g. an integer field with "", this should only be given if the editor was generated with the optional flag)

Complex editor, e.g. for records, should generate a checkbox to indicate that they are empty.

Proposal for new types:

:: Editor = {
...
valueFromState :: !EditState -> *EditorValue a
}

:: EditorValue a = ValidValue a | InvalidValue | EmptyValue