X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/sod/blobdiff_plain/d1b394fa5cde326c2635997ddb7cda27a52d537d..13cb243aea114b87d4382b8aaf1d357c9495dc0e:/doc/concepts.tex

diff --git a/doc/concepts.tex b/doc/concepts.tex
index b48746e..0f4b336 100644
--- a/doc/concepts.tex
+++ b/doc/concepts.tex
@@ -461,8 +461,96 @@ If there are no applicable primary methods then no effective method is
 constructed: the vtables contain null pointers in place of pointers to method
 entry functions.
 
+\begin{figure}
+  \begin{tikzpicture}
+    [>=stealth, thick,
+     order/.append style={color=green!70!black},
+     code/.append style={font=\sffamily},
+     action/.append style={font=\itshape},
+     method/.append style={rectangle, draw=black, thin, fill=blue!30,
+                           text height=\ht\strutbox, text depth=\dp\strutbox,
+                           minimum width=40mm}]
+
+    \def\delgstack#1#2#3{
+      \node (#10) [method, #2] {#3};
+      \node (#11) [method, above=6mm of #10] {#3};
+      \draw [->] ($(#10.north)!.5!(#10.north west) + (0mm, 1mm)$) --
+                 ++(0mm, 4mm)
+        node [code, left=4pt, midway] {next_method};
+      \draw [<-] ($(#10.north)!.5!(#10.north east) + (0mm, 1mm)$) --
+                 ++(0mm, 4mm)
+        node [action, right=4pt, midway] {return};
+      \draw [->] ($(#11.north)!.5!(#11.north west) + (0mm, 1mm)$) --
+                 ++(0mm, 4mm)
+        node [code, left=4pt, midway] {next_method}
+        node (ld) [above] {$\smash\vdots\mathstrut$};
+      \draw [<-] ($(#11.north)!.5!(#11.north east) + (0mm, 1mm)$) --
+                 ++(0mm, 4mm)
+        node [action, right=4pt, midway] {return}
+        node (rd) [above] {$\smash\vdots\mathstrut$};
+      \draw [->] ($(ld.north) + (0mm, 1mm)$) -- ++(0mm, 4mm)
+        node [code, left=4pt, midway] {next_method};
+      \draw [<-] ($(rd.north) + (0mm, 1mm)$) -- ++(0mm, 4mm)
+        node [action, right=4pt, midway] {return};
+      \node (p) at ($(ld.north)!.5!(rd.north)$) {};
+      \node (#1n) [method, above=5mm of p] {#3};
+      \draw [->, order] ($(#10.south east) + (4mm, 1mm)$) --
+                          ($(#1n.north east) + (4mm, -1mm)$)
+        node [midway, right, align=left]
+        {Most to \\ least \\ specific};}
+
+    \delgstack{a}{}{Around method}
+    \draw [<-] ($(a0.south)!.5!(a0.south west) - (0mm, 1mm)$) --
+               ++(0mm, -4mm);
+    \draw [->] ($(a0.south)!.5!(a0.south east) - (0mm, 1mm)$) --
+               ++(0mm, -4mm)
+      node [action, right=4pt, midway] {return};
+
+    \draw [->] ($(an.north)!.6!(an.north west) + (0mm, 1mm)$) --
+               ++(-8mm, 8mm)
+      node [code, midway, left=3mm] {next_method}
+      node (b0) [method, above left = 1mm + 4mm and -6mm - 4mm] {};
+    \node (b1) [method] at ($(b0) - (2mm, 2mm)$) {};
+    \node (bn) [method] at ($(b1) - (2mm, 2mm)$) {Before method};
+    \draw [->, order] ($(bn.west) - (6mm, 0mm)$) -- ++(12mm, 12mm)
+      node [midway, above left, align=center] {Most to \\ least \\ specific};
+    \draw [->] ($(b0.north east) + (-10mm, 1mm)$) -- ++(8mm, 8mm)
+      node (p) {};
+
+    \delgstack{m}{above right=1mm and 0mm of an.west |- p}{Primary method}
+    \draw [->] ($(mn.north)!.5!(mn.north west) + (0mm, 1mm)$) -- ++(0mm, 4mm)
+      node [code, left=4pt, midway] {next_method}
+      node [above right = 0mm and -8mm]
+      {$\vcenter{\hbox{\Huge\textcolor{red}{!}}}
+        \vcenter{\hbox{\begin{tabular}[c]{l}
+                         \textsf{next_method} \\
+                         pointer is null
+                       \end{tabular}}}$};
+
+    \draw [->, color=blue, dotted]
+        ($(m0.south)!.2!(m0.south east) - (0mm, 1mm)$) --
+        ($(an.north)!.2!(an.north east) + (0mm, 1mm)$)
+      node [midway, sloped, below] {Return value};
+
+    \draw [<-] ($(an.north)!.6!(an.north east) + (0mm, 1mm)$) --
+               ++(8mm, 8mm)
+      node [action, midway, right=3mm] {return}
+      node (f0) [method, above right = 1mm and -6mm] {};
+    \node (f1) [method] at ($(f0) + (-2mm, 2mm)$) {};
+    \node (fn) [method] at ($(f1) + (-2mm, 2mm)$) {After method};
+    \draw [<-, order] ($(f0.east) + (6mm, 0mm)$) -- ++(-12mm, 12mm)
+      node [midway, above right, align=center]
+      {Least to \\ most \\ specific};
+    \draw [<-] ($(fn.north west) + (6mm, 1mm)$) -- ++(-8mm, 8mm);
+
+  \end{tikzpicture}
+
+  \caption{The standard method combination}
+  \label{fig:concepts.methods.stdmeth}
+\end{figure}
+
 The effective method for a message with standard method combination works as
-follows.
+follows (see also~\xref{fig:concepts.methods.stdmeth}).
 \begin{enumerate}
 
 \item If any applicable methods have the @|around| role, then the most
@@ -769,7 +857,7 @@ be executed to set up a new instance.  Each superclass's initialization
 fragments are executed with @|me| bound to an instance pointer of the
 appropriate superclass type, immediately after that superclass's slots (if
 any) have been initialized; therefore, fragments defined by a more specific
-superclass are executed after fragments defined by a more specific
+superclass are executed after fragments defined by a less specific
 superclass.  A class may define more than one initialization fragment: the
 fragments are executed in the order in which they appear in the class
 definition.  It is possible for an initialization fragment to use @|return|
@@ -883,7 +971,7 @@ A class can define \emph{teardown fragments}: pieces of literal code to be
 executed to shut down an instance.  Each superclass's teardown fragments are
 executed with @|me| bound to an instance pointer of the appropriate
 superclass type; fragments defined by a more specific superclass are executed
-before fragments defined by a more specific superclass.  A class may define
+before fragments defined by a less specific superclass.  A class may define
 more than one teardown fragment: the fragments are executed in the order in
 which they appear in the class definition.  It is possible for an
 initialization fragment to use @|return| or @|goto| for special control-flow
