1 files changed, 148 insertions, 0 deletions
diff --git a/src/eval/array.rs b/src/eval/array.rs
new file mode 100644
index 00000000..f62bda9f
--- /dev/null
+++ b/src/eval/array.rs
@@ -0,0 +1,148 @@
+use std::fmt::{self, Debug, Formatter};
+use std::iter::FromIterator;
+use std::ops::{Add, AddAssign};
+use std::rc::Rc;
+
+use super::Value;
+
+/// Create a new [`Array`] from values.
+#[macro_export]
+macro_rules! array {
+    ($value:expr; $count:expr) => {
+        $crate::eval::Array::from_vec(vec![$crate::eval::Value::from($value); $count])
+    };
+
+    ($($value:expr),* $(,)?) => {
+        $crate::eval::Array::from_vec(vec![$($crate::eval::Value::from($value)),*])
+    };
+}
+
+/// A variably-typed array with clone-on-write value semantics.
+#[derive(Clone, PartialEq)]
+pub struct Array {
+    vec: Rc<Vec<Value>>,
+}
+
+impl Array {
+    /// Create a new, empty array.
+    pub fn new() -> Self {
+        Self { vec: Rc::new(vec![]) }
+    }
+
+    /// Create a new array from a vector of values.
+    pub fn from_vec(vec: Vec<Value>) -> Self {
+        Self { vec: Rc::new(vec) }
+    }
+
+    /// Create a new, empty array with the given `capacity`.
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self {
+            vec: Rc::new(Vec::with_capacity(capacity)),
+        }
+    }
+
+    /// Whether the array is empty.
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// The length of the array.
+    pub fn len(&self) -> usize {
+        self.vec.len()
+    }
+
+    /// Borrow the value at the given index.
+    pub fn get(&self, index: usize) -> Option<&Value> {
+        self.vec.get(index)
+    }
+
+    /// Mutably borrow the value at the given index.
+    pub fn get_mut(&mut self, index: usize) -> Option<&mut Value> {
+        Rc::make_mut(&mut self.vec).get_mut(index)
+    }
+
+    /// Set the value at the given index.
+    ///
+    /// This panics the `index` is out of range.
+    pub fn set(&mut self, index: usize, value: Value) {
+        Rc::make_mut(&mut self.vec)[index] = value;
+    }
+
+    /// Push a value to the end of the array.
+    pub fn push(&mut self, value: Value) {
+        Rc::make_mut(&mut self.vec).push(value);
+    }
+
+    /// Extend the array with the values from another array.
+    pub fn extend(&mut self, other: &Array) {
+        Rc::make_mut(&mut self.vec).extend(other.into_iter())
+    }
+
+    /// Clear the array.
+    pub fn clear(&mut self) {
+        if Rc::strong_count(&mut self.vec) == 1 {
+            Rc::make_mut(&mut self.vec).clear();
+        } else {
+            *self = Self::new();
+        }
+    }
+
+    /// Repeat this array `n` times.
+    pub fn repeat(&self, n: usize) -> Self {
+        let len = self.len().checked_mul(n).expect("capacity overflow");
+        self.into_iter().cycle().take(len).collect()
+    }
+
+    /// Iterate over references to the contained values.
+    pub fn iter(&self) -> std::slice::Iter<Value> {
+        self.vec.iter()
+    }
+
+    /// Iterate over the contained values.
+    pub fn into_iter(&self) -> impl Iterator<Item = Value> + Clone + '_ {
+        // TODO: Actually consume the vector if the ref-count is 1?
+        self.iter().cloned()
+    }
+}
+
+impl Default for Array {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Debug for Array {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        f.debug_list().entries(self.vec.iter()).finish()
+    }
+}
+
+impl FromIterator<Value> for Array {
+    fn from_iter<T: IntoIterator<Item = Value>>(iter: T) -> Self {
+        Array { vec: Rc::new(iter.into_iter().collect()) }
+    }
+}
+
+impl<'a> IntoIterator for &'a Array {
+    type Item = &'a Value;
+    type IntoIter = std::slice::Iter<'a, Value>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+impl Add<&Array> for Array {
+    type Output = Self;
+
+    fn add(mut self, rhs: &Array) -> Self::Output {
+        self.extend(rhs);
+        self
+    }
+}
+
+impl AddAssign<&Array> for Array {
+    fn add_assign(&mut self, rhs: &Array) {
+        self.extend(rhs);
+    }
+}