Added the functionality of split or clone.

I need more than the ability to clone nodes: I also need to split the
nodes.  Now this seems to be correctly added.

1 files changed, 35 insertions, 5 deletions

diff --git a/grammar/src/label.rs b/grammar/src/label.rs
index 3f89d9a..058baaf 100644
--- a/grammar/src/label.rs
+++ b/grammar/src/label.rs
@@ -12,6 +12,15 @@ pub enum GrammarLabelType {
     Rule(usize),
 }
 
+impl Display for GrammarLabelType {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            Self::TNT(tnt) => write!(f, "{tnt}"),
+            Self::Rule(pos) => write!(f, "R({pos})"),
+        }
+    }
+}
+
 // Some convenient conversions
 
 impl From<usize> for GrammarLabelType {
@@ -71,11 +80,17 @@ pub struct GrammarLabel {
 
 impl core::fmt::Display for GrammarLabel {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-        // Simply displaying this without the help of a grammar is not
-        // of much help, so we just use the debug method to cheat,
-        // haha.
-
-        write!(f, "{:?}", self)
+        write!(
+            f,
+            "{}, {}, {}",
+            self.label,
+            self.start,
+            if let Some(end) = self.end {
+                format!("{end}")
+            } else {
+                "ε".to_owned()
+            }
+        )
     }
 }
 
@@ -89,6 +104,15 @@ impl GrammarLabel {
         Self { label, start, end }
     }
 
+    /// Construct a new label with an ending position.
+    #[inline]
+    pub fn new_closed(label: impl Into<GrammarLabelType>, start: usize, end: usize) -> Self {
+        let label = label.into();
+        let end = Some(end);
+
+        Self { label, start, end }
+    }
+
     /// Return the end in the input.
     #[inline]
     pub fn end(&self) -> Option<usize> {
@@ -113,6 +137,12 @@ impl GrammarLabel {
         self.end = Some(end);
     }
 
+    /// Remove the ending boundary.
+    #[inline]
+    pub fn open_end(&mut self) {
+        self.end = None;
+    }
+
     /// Return a string description with the help of the associated
     /// grammar.
     pub fn to_string(&self, grammar: &Grammar) -> Result<String, Error> {