Compare functions and templates by identity

3 files changed, 56 insertions, 68 deletions

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index ba2de8c7..4992f70c 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -229,7 +229,10 @@ impl Eval for Rc<SyntaxTree> {
         let mut visitor = ExprVisitor { ctx, map: ExprMap::new() };
         visitor.visit_tree(self);
 
-        vec![TemplateNode::Tree { tree: Rc::clone(self), map: visitor.map }]
+        Rc::new(vec![TemplateNode::Tree {
+            tree: Rc::clone(self),
+            map: visitor.map,
+        }])
     }
 }
 
diff --git a/src/eval/ops.rs b/src/eval/ops.rs
index 01044842..3b48140c 100644
--- a/src/eval/ops.rs
+++ b/src/eval/ops.rs
@@ -1,35 +1,9 @@
 use std::cmp::Ordering::*;
+use std::rc::Rc;
 
 use super::{TemplateNode, Value};
 use Value::*;
 
-/// Join a value with another value.
-pub fn join(lhs: Value, rhs: Value) -> Result<Value, Value> {
-    Ok(match (lhs, rhs) {
-        (_, Error) => Error,
-        (Error, _) => Error,
-
-        (a, None) => a,
-        (None, b) => b,
-
-        (Str(a), Str(b)) => Str(a + &b),
-        (Array(a), Array(b)) => Array(concat(a, b)),
-        (Dict(a), Dict(b)) => Dict(concat(a, b)),
-
-        (Template(a), Template(b)) => Template(concat(a, b)),
-        (Template(mut a), Str(b)) => Template({
-            a.push(TemplateNode::Str(b));
-            a
-        }),
-        (Str(a), Template(mut b)) => Template({
-            b.insert(0, TemplateNode::Str(a));
-            b
-        }),
-
-        (a, _) => return Err(a),
-    })
-}
-
 /// Apply the plus operator to a value.
 pub fn pos(value: Value) -> Value {
     match value {
@@ -82,21 +56,7 @@ pub fn add(lhs: Value, rhs: Value) -> Value {
 
         (Fractional(a), Fractional(b)) => Fractional(a + b),
 
-        (Str(a), Str(b)) => Str(a + &b),
-        (Array(a), Array(b)) => Array(concat(a, b)),
-        (Dict(a), Dict(b)) => Dict(concat(a, b)),
-
-        (Template(a), Template(b)) => Template(concat(a, b)),
-        (Template(mut a), Str(b)) => Template({
-            a.push(TemplateNode::Str(b));
-            a
-        }),
-        (Str(a), Template(mut b)) => Template({
-            b.insert(0, TemplateNode::Str(a));
-            b
-        }),
-
-        _ => Error,
+        (a, b) => concat(a, b).unwrap_or(Value::Error),
     }
 }
 
@@ -130,6 +90,11 @@ pub fn sub(lhs: Value, rhs: Value) -> Value {
 
 /// Compute the product of two values.
 pub fn mul(lhs: Value, rhs: Value) -> Value {
+    fn repeat<T: Clone>(vec: Vec<T>, n: usize) -> Vec<T> {
+        let len = n * vec.len();
+        vec.into_iter().cycle().take(len).collect()
+    }
+
     match (lhs, rhs) {
         (Int(a), Int(b)) => Int(a * b),
         (Int(a), Float(b)) => Float(a as f64 * b),
@@ -258,17 +223,43 @@ pub fn range(lhs: Value, rhs: Value) -> Value {
     }
 }
 
-/// Concatenate two collections.
-fn concat<T, A>(mut a: T, b: T) -> T
-where
-    T: Extend<A> + IntoIterator<Item = A>,
-{
-    a.extend(b);
-    a
+/// Join a value with another value.
+pub fn join(lhs: Value, rhs: Value) -> Result<Value, Value> {
+    Ok(match (lhs, rhs) {
+        (_, Error) => Error,
+        (Error, _) => Error,
+
+        (a, None) => a,
+        (None, b) => b,
+
+        (a, b) => return concat(a, b),
+    })
 }
 
-/// Repeat a vector `n` times.
-fn repeat<T: Clone>(vec: Vec<T>, n: usize) -> Vec<T> {
-    let len = n * vec.len();
-    vec.into_iter().cycle().take(len).collect()
+/// Concatentate two values.
+fn concat(lhs: Value, rhs: Value) -> Result<Value, Value> {
+    Ok(match (lhs, rhs) {
+        (Str(a), Str(b)) => Str(a + &b),
+        (Array(mut a), Array(b)) => Array({
+            a.extend(b);
+            a
+        }),
+        (Dict(mut a), Dict(b)) => Dict({
+            a.extend(b);
+            a
+        }),
+        (Template(mut a), Template(b)) => Template({
+            Rc::make_mut(&mut a).extend(b.iter().cloned());
+            a
+        }),
+        (Template(mut a), Str(b)) => Template({
+            Rc::make_mut(&mut a).push(TemplateNode::Str(b));
+            a
+        }),
+        (Str(a), Template(mut b)) => Template({
+            Rc::make_mut(&mut b).insert(0, TemplateNode::Str(a));
+            b
+        }),
+        (a, _) => return Err(a),
+    })
 }
diff --git a/src/eval/value.rs b/src/eval/value.rs
index 472df0ea..07552c84 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -59,7 +59,7 @@ impl Value {
     where
         F: Fn(&mut ExecContext) + 'static,
     {
-        Self::Template(vec![TemplateNode::Func(TemplateFunc::new(f))])
+        Self::Template(Rc::new(vec![TemplateNode::Func(TemplateFunc::new(f))]))
     }
 
     /// The name of the stored value's type.
@@ -102,6 +102,7 @@ impl Value {
                 a.len() == b.len()
                     && a.iter().all(|(k, x)| b.get(k).map_or(false, |y| x.eq(y)))
             }
+            (Self::Template(a), Self::Template(b)) => Rc::ptr_eq(a, b),
             (a, b) => a == b,
         }
     }
@@ -153,7 +154,7 @@ pub type ArrayValue = Vec<Value>;
 pub type DictValue = BTreeMap<String, Value>;
 
 /// A template value: `[*Hi* there]`.
-pub type TemplateValue = Vec<TemplateNode>;
+pub type TemplateValue = Rc<Vec<TemplateNode>>;
 
 /// One chunk of a template.
 ///
@@ -177,7 +178,6 @@ pub enum TemplateNode {
 
 impl PartialEq for TemplateNode {
     fn eq(&self, _: &Self) -> bool {
-        // TODO: Figure out what we want here.
         false
     }
 }
@@ -205,13 +205,6 @@ impl TemplateFunc {
     }
 }
 
-impl PartialEq for TemplateFunc {
-    fn eq(&self, _: &Self) -> bool {
-        // TODO: Figure out what we want here.
-        false
-    }
-}
-
 impl Deref for TemplateFunc {
     type Target = dyn Fn(&mut ExecContext);
 
@@ -232,6 +225,7 @@ pub struct FuncValue {
     /// The string is boxed to make the whole struct fit into 24 bytes, so that
     /// a [`Value`] fits into 32 bytes.
     name: Option<Box<String>>,
+    /// The closure that defines the function.
     f: Rc<dyn Fn(&mut EvalContext, &mut FuncArgs) -> Value>,
 }
 
@@ -251,9 +245,9 @@ impl FuncValue {
 }
 
 impl PartialEq for FuncValue {
-    fn eq(&self, _: &Self) -> bool {
-        // TODO: Figure out what we want here.
-        false
+    fn eq(&self, other: &Self) -> bool {
+        // We cast to thin pointers because we don't want to compare vtables.
+        Rc::as_ptr(&self.f) as *const () == Rc::as_ptr(&other.f) as *const ()
     }
 }
 
@@ -620,7 +614,7 @@ primitive! { DictValue: "dictionary", Value::Dict }
 primitive! {
     TemplateValue: "template",
     Value::Template,
-    Value::Str(v) => vec![TemplateNode::Str(v)],
+    Value::Str(v) => Rc::new(vec![TemplateNode::Str(v)]),
 }
 primitive! { FuncValue: "function", Value::Func }