Class MosKey

Class MosKey provides part of the Muq support for the Muq Object System model of object-oriented computation. It is an internal support class normally only directly visible to -- or of interest to -- programmers venturing deep into the internals of Muq compilers and runtimes.

The MOS model requires that

• Generic functions be real compiled-functions, which can be called, applied &tc just like any normal compiledFunction.
• Generic functions be modifiable on the fly, adding and removing new methods and the like.
• Such modification may not actually change the idenity of the generic compiledFunction: The modified compiledFunction must be eq to the original.

Muq meets these requirements by implementing MOS generic functions as normal compiledFunction instances which happen to have (among other things) a special bit set identifying them as a MOS compiledFunction, and to have in their first constant slot a pointer to a MosKey instance, which then contains the time-varying information such as the currently-defined set of methods for the generic function.

A MosKey instance is itself neither a function nor a compiledFunction: It is merely a passive datastructure containing information about the generic function encoded for quick access during method invocation ("message-sending").

Class MosKey adds the following properties to those of Class Plain:

( Buggo, should merge type and layout, I think: )
$S.abstract              Normally NIL; non-NIL to forbid creation of instances.
$S.type                  'vector 'list or nil
$S.layout                Ram layout: :structure :vector :built-in :fixnum ...
$S.compiler              Parallel to function$s.compiler
$S.documentation         Value supplied to ]defclass :documentation option.
$S.source                Parallel to function$s.source
$S.fileName             Parallel to function$s.fileName
$S.fnLine               Parallel to function$s.fnLine
$S.assertion             Type verification compiledFunction.
$S.predicate             Type check compiled-funciton.
$S.printFunction        Print function.
$S.createdAnInstance   NIL unless an instances has been created.
$S.mosClass             Backpointer to MOS class we implement.
$S.newerKey             NIL, else pointer to key superceding us.
$S.concName             Prefix for accessor functions.
$S.constructor           Constructor compiledFunction.
$S.copier                Copier compiledFunction.
$S.named                 t or nil
$S.initialOffset        whole number
$S.export                NIL unless defstruct included :export t option.
$S.fertile               NIL unless subclassing by other users is ok.
$S.unsharedSlots        # of unshared slots (those stored in key).
$S.sharedSlots          # of shared slots (those stored in instances).
$S.mosParents           # of direct superclasses.
$S.mosAncestors         # of direct and indirect superclasses.
$S.initargs              # of initarg -> slotname map pairs.
$S.objectMmethods        # of methods keying on obj of our class in 1st arg.
$S.classMethods         # of methods keying on our class in 1st arg.
$S.metaclass             Currently always standardClass.

Note: For convenience, the $S properties are also available in the public (default) propdir.

MosKey instances also contain internal arrays with the above dimensions, in particular, the class precedence list: See section getMosKeyInitarg. See section getMosKeyInitarg. See section getMosKeyParent. See section setMosKeyParent. See section getMosKeyAncestor. See section setMosKeyAncestor. See section getMosKeySlotProperty. See section setMosKeySlotProperty.

See section makeMosKey.

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