1 files changed, 33 insertions, 1 deletions
diff --git a/src/type/mod.rs b/src/type/mod.rs
index 5e7076a..6c4be97 100644
--- a/src/type/mod.rs
+++ b/src/type/mod.rs
@@ -17,7 +17,10 @@ pub enum Type {
 
     List(Vec<Type>),
 
-    UndefinedType, // only for errors
+    /// Type for generics
+    /// and also error messages
+    /// with unknown types
+    VarType(String),
 
 }
 
@@ -27,6 +30,8 @@ pub enum TypeError {
 
     UndefinedVariable(String),
 
+    UnboundGeneric(String),
+
     InvalidOperator {
 	operator: SExp,
 	expected: Type,
@@ -41,3 +46,30 @@ pub enum TypeError {
 
     OtherError
 }
+
+
+impl Type {
+    /// Tests if the type has no variable types.
+    ///
+    /// **Examples**
+    /// ```rust
+    /// use melisp::r#type::{*, Type::*, TypeError::*, util::*};
+    ///
+    /// assert!(Integer.is_concrete());
+    /// assert!(!VarType("a".to_string()).is_concrete());
+    ///
+    /// assert!(arr(Integer, Integer).is_concrete());
+    /// assert!(!arr(VarType("b".to_string()), Integer).is_concrete());
+    ///
+    /// assert!(
+    ///     List(vec![Integer, Integer, arr(Integer, Integer)]).is_concrete()
+    /// );
+    /// assert!(
+    ///     !List(vec![Integer, VarType("a".to_string()), Integer])
+    ///         .is_concrete()
+    /// );
+    /// ```
+    pub fn is_concrete(&self) -> bool {
+        todo!()
+    }
+}