before a major refactor

I decide to adopt a new approach of recording and updating item
derivation forests.  Since this affects a lot of things, I decide to
commit before the refactor, so that I can create a branch for that
refactor.

1 files changed, 12 insertions, 4 deletions

diff --git a/semiring/src/lib.rs b/semiring/src/lib.rs
index 9d096db..6c0e0d5 100644
--- a/semiring/src/lib.rs
+++ b/semiring/src/lib.rs
@@ -15,6 +15,8 @@
 //! description.  Specifically, it will produce items as it parses the
 //! input string.  Then we can execute these items by any interpreter.
 
+use grammar::Grammar;
+
 /// A semiring is equipped with two operations: the addition and the
 /// multiplication.  It also has additive and multiplicative
 /// identities.  Also the two operations are supposed to be
@@ -29,14 +31,20 @@ pub trait Semiring {
     fn one() -> Self;
 
     /// The addition.
-    fn add(&mut self, other: impl AsRef<Self>);
+    fn add(&mut self, other: &Self);
 
     /// The multiplication.
-    fn mul(&mut self, other: impl AsRef<Self>);
+    fn mul(&mut self, other: &Self);
+
+    /// A valuation associates a semiring value from a rule position.
+    ///
+    /// Since a position is not complete without a grammar, we also
+    /// give it a grammar.
+    fn valuation(pos: usize, grammar: &Grammar) -> Self;
 }
 
-// TODO: Implement boolean semiring
-// TODO: Implement counting semiring
+pub mod counting;
+
 // TODO: Implement derivation forest semiring
 
 #[cfg(test)]