Save before system restart.

I am about to re-start my system, so I save before any crashes
happen.

1 files changed, 26 insertions, 2 deletions

diff --git a/chain/src/plan.org b/chain/src/plan.org
index 75acf30..bbd6683 100644
--- a/chain/src/plan.org
+++ b/chain/src/plan.org
@@ -38,11 +38,30 @@
       finite automata.
     * [X] Test the removal of dead states, where a state is dead if
       and only if no other states have an edge into that state.
-- [-] Refactor [2/5]
+- [-] Refactor [2/8]
   + [X] Implement a data type for graphs with labels on vertices and
     edges, but do not need to index edges by labels, which can index
     vertices by labels instead.
+    * [X] Test it.
   + [X] Implement a builder that borrows a graph mutably.
+    * [X] Test it.
+  + [ ] Implement a data type for graphs in which every node knows its
+    parents, and every node has a unique label but edges have no
+    labels.
+    * [ ] Test it.
+  + [ ] We need to record the expansions of those "virtual nodes".
+    That is, the virtual nodes represent atomic languages such as
+    [s]^{(t)} where s is a non-terminal and t is a terminal.  To be more
+    specific, it represents the derivative of the left-linear closure
+    of the non-terminal s with respect to the terminal t.  The
+    left-linear closure of s is the set of all strings (consisting of
+    terminals and non-terminals alike) that are derivable from s
+    alone, without consuming any inputs, by expanding according to the
+    grammar rules.  This means that we need to know which
+    non-terminals were expanded in order to get to a state in [s]^{(t)}.
+  + [ ] Each edge in the chain-rule machine needs to be labelled also
+    with a position in the forest.  This perfectly solves the problem
+    of those "plugs"!
   + [ ] When we pull in some regular language because of the
     left-linear expansion, we need to mark that branch as coming from
     left-linear expansions.  This is necessary because we cannot
@@ -66,7 +85,12 @@
   + [X] First define a trait with the expected behaviours.
   + [ ] Then implement them as doubly labelled graphs.
   + [ ] Thenimplement finding derivatives by use of the chain rule.
-- [-] Implement forests [1/2]
+- [-] Implement forests [2/3]
+  + [X] Design a format of forests.  This should be the most crucial
+    thing to do, in order to have a better understanding of the whole
+    picture.  I need to have a clear understanding of the details of
+    the binarised shared packed parsed forests, that reflects the
+    regular expressions in the grammar equations.
   + [X] Define a trait with the expected behaviours.
   + [-] Implement them using adjacency map: we only need one label per
     edge, and we do not wish to exclude duplicate edges, and we do not