\end{enumerate}
Keyword arguments are provided as a general feature for C functions.
+However, Sod has special support for messages which accept keyword arguments
+(\xref{sec:concepts.methods.keywords}).
%%%--------------------------------------------------------------------------
\section{Messages and methods} \label{sec:concepts.methods}
$M$ is a more (resp.\ less) specific superclass of~$C$ than the class
defining $N$.
-\subsection{The standard method combination}
-\label{sec:concepts.methods.standard}
-
+\subsubsection{The standard method combination}
The default method combination is called the \emph{standard method
combination}; other method combinations are useful occasionally for special
effects. The standard method combination accepts four direct method roles,
-called @|primary| (the default), @|before|, @|after|, and @|around|.
+called `primary' (the default), @|before|, @|after|, and @|around|.
All direct methods subject to the standard method combination must have
argument lists which \emph{match} the message's argument list:
dynamic environment appropriately for the primary methods of its subclasses,
e.g., by claiming a lock, and restore it afterwards.
-The @|next_method| function provided to methods with the @|primary| and
+The @|next_method| function provided to methods with the primary and
@|around| roles accepts the same arguments, and returns the same type, as the
message, except that one or two additional arguments are inserted at the
front of the argument list. The first additional argument is always the
of the argument pointer (so the method body can process the variable argument
suffix itself, and still pass a fresh copy on to the next method).
-A method with the @|primary| or @|around| role may use the convenience macro
+A method with the primary or @|around| role may use the convenience macro
@|CALL_NEXT_METHOD|, which takes no arguments itself, and simply calls
@|next_method| with appropriate arguments: the receiver @|me| pointer, the
argument pointer @|sod__master_ap| (if applicable), and the method's
@|CALL_NEXT_METHOD| will pass along the updated values, rather than the
original ones.
-\subsection{Aggregating method combinations}
-\label{sec:concepts.methods.aggregating}
-
+\subsubsection{Aggregating method combinations}
A number of other method combinations are provided. They are called
`aggregating' method combinations because, instead of invoking just the most
specific primary method, as the standard method combination does, they invoke
There is also a @|custom| aggregating method combination, which is described
in \xref{sec:fixme.custom-aggregating-method-combination}.
+
+\subsection{Messages with keyword arguments}
+\label{sec:concepts.methods.keywords}
+
+A message or a direct method may declare that it accepts keyword arguments.
+A message which accepts keyword arguments is called a \emph{keyword message};
+a direct method which accepts keyword arguments is called a \emph{keyword
+method}.
+
+While method combinations may set their own rules, usually keyword methods
+can only be defined on keyword messages, and all methods defined on a keyword
+message must be keyword methods. The direct methods defined on a keyword
+message may differ in the keywords they accept, both from each other, and
+from the message. If two superclasses of some common class both define
+keyword methods on the same message, and the methods both accept a keyword
+argument with the same name, then these two keyword arguments must also have
+the same type. Different applicable methods may declare keyword arguments
+with the same name but different defaults; see below.
+
+The keyword arguments acceptable in a message sent to an object are the
+keywords listed in the message definition, together with all of the keywords
+accepted by any applicable method. There is no easy way to determine at
+runtime whether a particular keyword is acceptable in a message to a given
+instance.
+
+At runtime, a direct method which accepts one or more keyword arguments
+receives an additional argument named @|suppliedp|. This argument is a small
+structure. For each keyword argument named $k$ accepted by the direct
+method, @|suppliedp| contains a one-bit-wide bitfield member of type
+@|unsigned|, also named $k$. If a keyword argument named $k$ was passed in
+the message, then @|suppliedp.$k$| is one, and $k$ contains the argument
+value; otherwise @|suppliedp.$k$| is zero, and $k$ contains the default value
+from the direct method definition if there was one, or an unspecified value
+otherwise.
+
%%%--------------------------------------------------------------------------
\section{Metaclasses} \label{sec:concepts.metaclasses}
~mdw / sod / blobdiff