renaming core to chain and some other changes

Some changes:

- The core crate is renamed to "chain".

- The crate "viz" is added, which will provide layered graph drawing
  algorithms.

- A function is added to convert from a grammar to the regular
  language of its left-linear closures.

- A function is added to convert from a nondeterministic finite
  automaton to its "null" closure.  A null closure is the same
  automaton with edges added, as if some edges are "null".  Whether an
  edge is null is determined by a function.
  Combined with the previous change, we can convert a grammar to the
  regular language of the null closure of its left-linear closures.

---

Now it remains to test more grammars and add an Atom trait, before
finishing the part about compilations.

1 files changed, 0 insertions, 20 deletions

diff --git a/repcore/src/lib.rs b/repcore/src/lib.rs
deleted file mode 100644
index 589b61c..0000000
--- a/repcore/src/lib.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-//! This package implements the core algorithm of the entire
-//! workspace: parsing with derivatives by means of regular nulling
-//! languages.
-
-pub mod grammar;
-
-pub fn add(left: usize, right: usize) -> usize {
-    left + right
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
-    }
-}