object types: ket

        |some text label>
        c|another text label>
        kets are the fundamental building block of the SDB project
        in essence everything is either a ket or an operator
        the text label of a ket is an almost arbitrary string
        with the exception that it can't contain the < | or > symbols
        the so called coefficient of a ket is a float, usually positive
        if the coefficient is not given then it has coefficient == 1
        colons in the ket label notate the category of the object
        |food: bread> says that bread is in the category of food
        one interpretation of a ket is a single synapse in a brain
        where the coefficient represents the activity of that synapse over some small time window
        and the ket label is just some useful label for that synapse
        another interpretation of a ket is a single node in a directed graph
        NB: in the back-end code, the ket label strings are mapped to unique integers

        -- kets can represent concepts:
        -- eg, a little hungry:

        -- eg, very tired:

        -- noun's:
        |person: Fred Smith>

        -- proper noun's:
        |city of Adelaide>

        -- numbers:

        -- point on a number line:
        |x: 9>

        -- a 2D co-ordinate:
        |3: 11>

    see also:
        superposition, sequence