X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=topbloke-formulae.git;a=blobdiff_plain;f=notation.tex;h=b6b4a8cc814c01ffdb9076320796fbadfbc4bfbd;hp=966c51ec5cd64a6178b9b11bf50b367218ff77db;hb=1768ad396360b5f7145450858b4bae1e9d1c7b05;hpb=891ae7626916bde1eb7dfa38762bbb4d94b85211

diff --git a/notation.tex b/notation.tex
index 966c51e..b6b4a8c 100644
--- a/notation.tex
+++ b/notation.tex
@@ -1,9 +1,15 @@
-\section{Notation}
+\stdsection{Notation}
+
+Throughout, any free variables are implicitly universally quantified
+at the outermost level.
 
 \begin{basedescript}{
 \desclabelwidth{5em}
 \desclabelstyle{\nextlinelabel}
 }
+\item[ $ C \hasparent D $ ]
+Commit $C$ has commit $D$ as (one of) its parents.
+
 \item[ $ C \hasparents \set X $ ]
 The parents of commit $C$ are exactly the set
 $\set X$.
@@ -11,7 +17,7 @@ $\set X$.
 \item[ $ C \ge D $ ]
 $C$ is a descendant of $D$ in the git commit
 graph.  This is a partial order, namely the transitive closure of
-$ D \in \set X $ where $ C \hasparents \set X $.
+$ \hasparent $.
 
 \item[ $ C \has D $ ]
 Informally, the tree at commit $C$ contains the change
@@ -28,12 +34,20 @@ are respectively the base and tip git branches.  $\p$ may be used
 where the context requires a set, in which case the statement
 is to be taken as applying to both $\py$ and $\pn$.
 All of these sets will be disjoint by construction
-(see Invariants, below).  Hence:
+(see Invariants, below).
+
+\item[ $\foreign$ ]
+The set of all commits which are not part of a Topbloke branch.  We
+call these foreign commits.  Hence:
 
 \item[ $ \patchof{ C } $ ]
-Either $\p$ s.t. $ C \in \p $, or $\bot$.
+Either $\p$ s.t. $ C \in \p $, or $\foreign$.
 A function from commits to patches' sets $\p$.
 
+\item[ $\set A$, $\set P$, $\ldots$ ]
+Arbitrary sets of commits.  Maybe $\set P = \p$ i.e.\ some $\py$ or $\pn$, but
+maybe not.
+
 \item[ $ \pancsof{C}{\set P} $ ]
 $ \{ A \; | \; A \le C \land A \in \set P \} $
 i.e. all the ancestors of $C$
@@ -75,15 +89,42 @@ the relevant Topbloke branches, we hope that
 if the user still cares about the Topbloke patch,
 git's merge algorithm will DTRT when trying to re-apply the changes.
 
-\item[ $\displaystyle \mergeof{C}{L}{M}{R} $ ]
-The contents of a git merge result:
+\item[ $\displaystyle \stmtmergeof{\stmt L}{\stmt M}{\stmt R} $ ]
+The proper results of a merge.  Formally,
+where $\stmt L$, $\stmt M$ and $\stmt R$ are statements:
+$$
+  \stmtmergeof{\stmt L}{\stmt M}{\stmt R}
+    \equiv
+  \begin{cases}
+         (\stmt L \land \stmt R)      : & \true \\
+    (\neg \stmt L \land \neg \stmt R) : & \false \\
+    \text{otherwise} : & \neg \stmt M
+  \end{cases}
+$$
+
+May also be used with sets:
+$$
+  \setmergeof{\set L}{\set M}{\set R}
+     =
+  \left\{
+    \;
+    D \; \middle| \;
+      \setmergeof{ D \in \set L }{ D \in \set M }{ D \in \set R }
+    \;
+  \right\}
+$$
+
+\item[ $\displaystyle \commitmergeof{C}{L}{M}{R} $ ]
+With $C$, $L$, $M$ and $R$ being commits, a convenience notation.
+$C$ has exactly the contents of a git merge result:
 
 $\displaystyle D \isin C \equiv
   \begin{cases}
-    (D \isin L \land D \isin R) \lor D = C : & \true \\
-    (D \not\isin L \land D \not\isin R) \land D \neq C : & \false \\
-    \text{otherwise} : & D \not\isin M
+    D = C : & \true \\
+    D \neq C : & \stmtmergeof{ D \isin L }{ D \isin M }{ D \isin R }
   \end{cases}
 $
 
+We will refer to this as \bf\commitmergename.
+
 \end{basedescript}