preferences:set-un/marshall in Framework Functions

• (preferences:set-un/marshall symbol marshall unmarshall) -> void?
     symbol : symbol?
     marshall : (any/c . -> . printable/c)
     unmarshall : (printable/c . -> . any/c)

  preference:set-un/marshall is used to specify marshalling and unmarshalling functions for the preference symbol. marshall will be called when the users saves their preferences to turn the preference value for symbol into a printable value. unmarshall will be called when the user's preferences are read from the file to transform the printable value into it's internal representation. If preference:set-un/marshall is never called for a particular preference, the values of that preference are assumed to be printable.

  If the unmarshalling function returns a value that does not meet the guard passed to preferences:set-default for this preference, the default value is used.

  The marshall function might be called with any value returned from read and it must not raise an error (although it can return arbitrary results if it gets bad input). This might happen when the preferences file becomes corrupted, or is edited by hand.

  preference:set-un/marshall must be called before calling preferences:get, preferences:set.