1 files changed, 59 insertions, 0 deletions
diff --git a/repcore/src/grammar.rs b/repcore/src/grammar.rs
new file mode 100644
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--- /dev/null
+++ b/repcore/src/grammar.rs
@@ -0,0 +1,59 @@
+//! This file implements the extected behaviours of grammars.
+
+// NOTE: We shall first start with a parser that works at the level of
+// characters.  The purpose is to first experiment with the workings
+// and the performance of the algorithms, before optimising by using
+// regular expressions to classify inputs into tokens.  In other
+// words, the current focus is not on the optimisations, whereas
+// scanners are for optimisations only, so to speak.
+
+/// The type of a terminal.
+///
+/// For the time being this is a wrapper around a string, but in the
+/// future it may hold more information of scanners.
+pub struct Terminal {
+    // If we want to use scanners, per chance add them as a new field
+    // here.
+    name: String,
+}
+
+impl Terminal {
+    /// Create a terminal with the given name.
+    #[inline]
+    pub fn new(name: String) -> Self {
+        Self { name }
+    }
+
+    /// Return the name of the terminal.
+    #[inline]
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+}
+
+/// The type of a non-terminal.
+///
+/// This is just a wrapper around a string.
+pub struct Nonterminal(String);
+
+impl Nonterminal {
+    /// Return the name of the nonterminal.
+    ///
+    /// Just to improve readability.
+    #[inline]
+    pub fn name(&self) -> &str {
+        &self.0
+    }
+}
+
+/// The type of a terminal or a non-terminal.
+///
+/// Only an index is stored here.  Actual data are stored in two other
+/// arrays.
+#[derive(Debug, Hash, Eq, PartialEq, Clone, Copy, Ord, PartialOrd)]
+pub enum TNT {
+    /// Terminal variant
+    Ter(usize),
+    /// Nonterminal variant
+    Non(usize),
+}