1 files changed, 60 insertions, 0 deletions
diff --git a/src/modelica_ast.rs b/src/modelica_ast.rs
index cbb82ea..2828f81 100644
--- a/src/modelica_ast.rs
+++ b/src/modelica_ast.rs
@@ -79,6 +79,10 @@ impl ModelicaModel {
         binds
     }
 
+    // This crude function finds "unbound" variables: those which are not constants, parameters, or
+    // the sole element on the LHS of an equation.
+    // Bugs:
+    //   if a var is on LHS and RHS of same equation
     pub fn get_free_vars(&self) -> Vec<String> {
         // Start with components, and remove constants and parameters
         let vars = self.components.iter().filter(|v| match v.prefix {
@@ -100,6 +104,62 @@ impl ModelicaModel {
     }
 }
 
+impl Expr {
+
+    // Order is undefined
+    pub fn identifiers(&self) -> Vec<String> {
+        use self::Expr::*;
+        match *self {
+            Integer(_) | Float(_) => vec![],
+            Ident(ref s) => vec![s.clone()],
+            Der(ref e) | Abs(ref e) => e.identifiers(),
+            BinExpr(_, ref e1, ref e2) => {
+                let mut all = e1.identifiers();
+                for i in e2.identifiers() {
+                    if !(all.contains(&i)) {
+                        all.push(i.clone());
+                    }
+                }
+                all
+            },
+        }
+    }
+}
+
+#[test]
+fn test_expr_identifiers() {
+    use self::Expr::*;
+
+    fn set_eq(a: Vec<String>, b: Vec<String>) -> bool {
+        let set_a: HashSet<String> = HashSet::from_iter(a);
+        let set_b: HashSet<String> = HashSet::from_iter(b);
+        return set_a == set_b;
+    }
+
+    assert!(set_eq(
+        vec![],
+        Integer(0).identifiers()));
+    assert!(set_eq(
+        vec!["x".to_string()],
+        Ident("x".to_string()).identifiers()));
+    assert!(set_eq(
+        vec!["x".to_string(), "y".to_string(), "z".to_string()],
+        BinExpr(BinOperator::Add,
+            Box::new(Abs(Box::new(Ident("z".to_string())))),
+            Box::new(BinExpr(BinOperator::Add,
+                Box::new(Abs(Box::new(Ident("x".to_string())))),
+                Box::new(Abs(Box::new(Ident("y".to_string()))))))).identifiers()));
+    assert!(set_eq(
+        vec!["z".to_string()],
+        BinExpr(BinOperator::Add,
+            Box::new(Ident("z".to_string())),
+            Box::new(Ident("z".to_string()))).identifiers()));
+}
+
+impl SimpleEquation {
+}
+
+
 //// Debug Implementations
 
 impl Debug for ModelicaModel {