Re: Clarification

[Danny Bobrow <Bobrow.pa@Xerox.COM>]

    We propose the following fair copy:

    ``The slot options provided by the various slot descriptions
    combine as follows:

    The {\bf :allocation} option is inherited from the most
    specific class in the class precedence list. If no superclass
    explicitly specifies the {\bf :allocation} option, the default is
    {\bf :allocation} {\bf :instance}.''

    Note that this definition is intended to be recursive, because
    there might be no class that explicitly specifies the :allocation
    option.

The only issue this skirts is the following example that has a problem:

(defclass A () ((s :initform 1 :allocation :class)))

(defclass B (A)((s :initform 2)))

The latter MUST mean :allocation :instance (or signal an error).  I
think we should insist that :allocation :class be repeated if it is
intended to change anything else about the class variable (this is the
only sane semantic interpretation).   Another alternative is to make
there be a different class variable in B.  

For :dynamic, this kind of example makes sense (there is a different
value stored in a different class).  But on the principle that the
unusual case (namely anything but :allocation :instance) ought to be
visible locally. I would say that if a local description appears in a
class, then allocation is :instance, unless overridden locally.  Or
stronger, if allocation inherited is anything but :instance, then an
error is signalled if no :allocation is specified locally.  Which of
these two do you like?