1 files changed, 91 insertions, 0 deletions
diff --git a/src/chomp/set.rs b/src/chomp/set.rs
new file mode 100644
index 0000000..0661ab6
--- /dev/null
+++ b/src/chomp/set.rs
@@ -0,0 +1,91 @@
+use std::collections::BTreeSet;
+
+#[derive(Clone, Debug, Default, Eq, PartialEq, Hash)]
+pub struct FirstSet {
+    inner: BTreeSet<char>,
+}
+
+impl FirstSet {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn of_str(s: &str) -> Self {
+        let mut inner = BTreeSet::new();
+        s.chars().next().map(|c| inner.insert(c));
+
+        Self { inner }
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    pub fn union(mut self, mut other: Self) -> Self {
+        self.inner.append(&mut other.inner);
+        self
+    }
+
+    pub fn intersect(&self, other: &Self) -> Self {
+        Self {
+            inner: self.inner.intersection(&other.inner).copied().collect(),
+        }
+    }
+}
+
+impl IntoIterator for FirstSet {
+    type Item = char;
+
+    type IntoIter = <BTreeSet<char> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.into_iter()
+    }
+}
+
+#[derive(Clone, Debug, Default, Eq, PartialEq, Hash)]
+pub struct FlastSet {
+    inner: BTreeSet<char>,
+}
+
+impl FlastSet {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    pub fn union_first(mut self, mut other: FirstSet) -> Self {
+        self.inner.append(&mut other.inner);
+        self
+    }
+
+    pub fn union(mut self, mut other: Self) -> Self {
+        self.inner.append(&mut other.inner);
+        self
+    }
+
+    pub fn intersect_first(&self, other: &FirstSet) -> Self {
+        Self {
+            inner: self.inner.intersection(&other.inner).copied().collect(),
+        }
+    }
+
+    pub fn intersect(&self, other: &Self) -> Self {
+        Self {
+            inner: self.inner.intersection(&other.inner).copied().collect(),
+        }
+    }
+}
+
+impl IntoIterator for FlastSet {
+    type Item = char;
+
+    type IntoIter = <BTreeSet<char> as IntoIterator>::IntoIter;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.inner.into_iter()
+    }
+}