The mode selectors for emitting JSON texts from opaque values.

Use mode () to create a mode selector record for the opaque value emitter. Use any of the various optional parameters to set a mode selector to other than its default value.

No selector modes are defined at present.

Use value () to create an opaque value emitter. The following table describes the runtime type indications required for values emitted.

• null: Cf_type.Unit
• boolean: Cf_type.Bool
• number: Cf_type.Int or Cf_type.Float
• string: Cf_type.String or Ucs_type.Text
• array: Cf_type.(Seq Opaque)
• object: Cf_type.(Seq (Pair (Opaque, Opaque))

Use the ~mode parameter to select modes other than the default. Raises Invalid_argument if the witnessed type is not valid for output as a JSON value.

Note well: the first opaque value of each pair element in an object value must be witness either by Ucs_type.Text or Cf_type.String.

Use to_text v to format v as a Unicode text. Use ~mode to select the encoding modes. Raises Invalid_argument if v was not witnessed with a type compatible with JSON encoding.