a prototype of an item derivation forest

It seems to be complete now, but still awaits more tests to see where
the errors are, which should be plenty, haha.

2 files changed, 48 insertions, 30 deletions

diff --git a/grammar/src/label.rs b/grammar/src/label.rs
index 05b0b1e..3f89d9a 100644
--- a/grammar/src/label.rs
+++ b/grammar/src/label.rs
@@ -12,15 +12,50 @@ pub enum GrammarLabelType {
     Rule(usize),
 }
 
+// Some convenient conversions
+
+impl From<usize> for GrammarLabelType {
+    #[inline]
+    fn from(r: usize) -> Self {
+        Self::Rule(r)
+    }
+}
+
+impl From<TNT> for GrammarLabelType {
+    #[inline]
+    fn from(tnt: TNT) -> Self {
+        Self::TNT(tnt)
+    }
+}
+
 impl GrammarLabelType {
     /// Return the name of this label with the help of the associated
     /// grammar.
+    #[inline]
     pub fn name(&self, grammar: &Grammar) -> Result<String, Error> {
         match self {
             Self::TNT(tnt) => grammar.name_of_tnt(*tnt),
             Self::Rule(pos) => grammar.rule_pos_to_string(*pos),
         }
     }
+
+    /// Return the contained TNT, if any.
+    #[inline]
+    pub fn tnt(&self) -> Option<TNT> {
+        match self {
+            Self::TNT(tnt) => Some(*tnt),
+            Self::Rule(_) => None,
+        }
+    }
+
+    /// Return the contained rule position, if any.
+    #[inline]
+    pub fn rule(&self) -> Option<usize> {
+        match self {
+            Self::TNT(_) => None,
+            Self::Rule(pos) => Some(*pos),
+        }
+    }
 }
 
 /// The label to be used in a forest.
@@ -32,8 +67,6 @@ pub struct GrammarLabel {
     start: usize,
     /// The end in the input that this label correponds to.
     end: Option<usize>,
-    /// A node in the forest might be a packed node.
-    packed_p: bool,
 }
 
 impl core::fmt::Display for GrammarLabel {
@@ -48,54 +81,44 @@ impl core::fmt::Display for GrammarLabel {
 
 impl GrammarLabel {
     /// Construct a new label.
-    pub fn new(label: GrammarLabelType, start: usize) -> Self {
+    #[inline]
+    pub fn new(label: impl Into<GrammarLabelType>, start: usize) -> Self {
+        let label = label.into();
         let end = None;
-        let packed_p = false;
 
-        Self {
-            label,
-            start,
-            end,
-            packed_p,
-        }
+        Self { label, start, end }
     }
 
     /// Return the end in the input.
+    #[inline]
     pub fn end(&self) -> Option<usize> {
         self.end
     }
 
     /// Return the start in the input.
+    #[inline]
     pub fn start(&self) -> usize {
         self.start
     }
 
     /// Return the actual label.
+    #[inline]
     pub fn label(&self) -> GrammarLabelType {
         self.label
     }
 
     /// Update the end.
+    #[inline]
     pub fn set_end(&mut self, end: usize) {
         self.end = Some(end);
     }
 
-    /// Check whether the node is a packed node.
-    pub fn is_packed(&self) -> bool {
-        self.packed_p
-    }
-
-    /// Update the packed status.
-    pub fn set_packed_p(&mut self, packed_p: bool) {
-        self.packed_p = packed_p;
-    }
-
     /// Return a string description with the help of the associated
     /// grammar.
     pub fn to_string(&self, grammar: &Grammar) -> Result<String, Error> {
         // First calculate the length of the resulting string.
 
-        let mut num = 2 + 7 + 14 + 6;
+        let mut num = 16 + 6;
 
         num += self.label().name(grammar)?.len();
 
@@ -111,15 +134,7 @@ impl GrammarLabel {
 
         let mut s = String::with_capacity(num);
 
-        s.push_str("a ");
-
-        if self.is_packed() {
-            s.push_str("packed ");
-        } else {
-            s.push_str("normal ");
-        }
-
-        s.push_str("node labelled ");
+        s.push_str("a node labelled ");
 
         s.push_str(&self.label().name(grammar)?);
 
diff --git a/grammar/src/lib.rs b/grammar/src/lib.rs
index b29fc69..2c17a5f 100644
--- a/grammar/src/lib.rs
+++ b/grammar/src/lib.rs
@@ -486,6 +486,9 @@ impl Grammar {
             .contains(&None))
     }
 
+    // FIXME: We shall use a label to query this information as well,
+    // probably.
+
     /// Query the expansion information from the position `pos1` to
     /// the position `pos2` .
     #[inline]