Re: [Chicken-users] New immediate values (was: DBI)

[John Cowan]

Thomas Chust scripsit:

> So if you considered NULL as being a marker for the absence of any real 
> value, its type would be the empty set which is a subset of every other 
> type.

And yet the null set contains, per definitionem, no members at all,
whether null or otherwise.  A paradox, and very appropriate for this
bissextile day!  Here's a song from Gilbert and Sullivan's comic operetta
_The Pirates of Penzance_, where the hero Frederic is by an agreement
of indenture to be a pirate's apprentice until his 21st *birthday*:

        Ruth.   
        When you had left our pirate fold,
        We tried to raise our spirits faint,
        According to our custom old,
        With quip and quibble quaint.
        But all in vain the quips we heard,
        We lay and sobbed upon the rocks,
        Until to somebody occurred
        A startling paradox.

        Frederic.
        A paradox?

        Ruth. (laughing)
        A paradox,
        A most ingenious paradox!
        We've quips and quibbles heard in flocks,
        But none to beat this paradox!

        All.
        A paradox, a paradox,
        A most ingenious paradox.
        Ha, ha, ha, ha, ha, ha, ha, ha,
        This paradox.

        Pirate King.    
        We knew your taste for curious quips,
        For cranks and contradictions queer;
        And with the laughter on our lips,
        We wished you there to hear.
        We said, "If we could tell it him,
        How Frederic would the joke enjoy!"
        And so we've risked both life and limb
        To tell it to our boy.

        Frederic. (interested)
        A paradox?

        King. (laughing)

        A paradox,
        That most ingenious paradox!
        We've quips and quibbles heard in flocks,
        But none to beat that paradox!

        All.
        A paradox, a paradox,
        A most ingenious paradox.
        Ha, ha, ha, ha, ha, ha, ha, ha,
        That paradox.

        King (recitative).
        For some ridiculous reason, to which, however, I've no desire to be 
disloyal,
        Some person in authority, I don't know who, very likely the Astronomer 
Royal,
        Has decided that, although for such a beastly month as February,
                twenty-eight days as a rule are plenty,
        One year in every four his days shall be reckoned as nine and twenty.
        Through some singular coincidence -- I shouldn't be surprised if it 
were owing to the
                agency of an ill-natured fairy --
        You are the victim of this clumsy arrangement, having been born in 
leap-year,
                on the twenty-ninth of February;
        And so, by a simple arithmetical process, you'll easily discover,
        That though you've lived twenty-one years, yet, if we go by birthdays,
                you're only five and a little bit over!

        Ruth & King.
        Ha! ha! ha! ha! ha! ha!
        Ho! ho! ho! ho!

        Frederic.
        Dear me!
        Let's see! (counting on fingers)
        Yes, yes; with yours my figures do agree!

        Ruth & King.
        Ha! ha! ha! ha! ha! ha! ha! ha!

        Frederic. (more amused than any)
        How quaint the ways of Paradox!
        At common sense she gaily mocks!
        Though counting in the usual way,
        Years twenty-one I've been alive.
        Yet, reckoning by my natal day,
        Yet, reckoning by my natal day,
        I am a little boy of five!

        Ruth & King.
        He is a little boy of five!

        All.
        Ha, ha, ha, ha, ha, ha, ha, ha,
        A paradox, a paradox,
        A most ingenious paradox.
        Ha, ha, ha, ha, ha, ha, ha, ha,
        A paradox.
        Ha, ha, ha, ha, ha, ha, ha, ha,
        A curious paradox,
        Ha, ha, ha, ha, ha, ha, ha, ha, ha,
        A most ingenious paradox.

So rather than being free of his indenture on 29 February 1877, the
date of the action, Frederic must remain with the pirates until 1940!
(Gilbert overlooked the fact that 1900 was not a leap year; the
alternative date of 1873 is ruled out by internal evidence.)

> This is not the only possible interpretation of NULL, though, and whether 
> it is a useful one may depend on the situation ;-)

In fact the paradox is easily disposed of:  while the null value
*semantically* indicates the absence of information, either because it
is unknown, or (less defensibly) because it cannot exist (e.g., the
name of the spouse of an unmarried person), it is *formally* a value
like any other, and its type is a singleton set.

> Nevertheless I think it is pretty bad practice to call a static method on 
> an instance instead of the class itself...

Indeed.

-- 
John Cowan  http://ccil.org/~cowan    address@hidden
There are books that are at once excellent and boring.  Those that at
once leap to the mind are Thoreau's Walden, Emerson's Essays, George
Eliot's Adam Bede, and Landor's Dialogues.  --Somerset Maugham