2 files changed, 35 insertions, 0 deletions
diff --git a/src/lib.rs b/src/lib.rs
index 1eabc19..ee6c22e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,2 +1,3 @@
 pub mod sexp;
 pub mod parse;
+pub mod r#type;
diff --git a/src/type/mod.rs b/src/type/mod.rs
new file mode 100644
index 0000000..623edc9
--- /dev/null
+++ b/src/type/mod.rs
@@ -0,0 +1,34 @@
+
+use crate::sexp::{SExp, SExp::*};
+
+pub enum Type {
+    Integer,
+    Arrow(Box<Type>, Box<Type>),
+}
+
+pub enum TypeError {
+    UndefinedVariable(String),
+    InvalidOperator {
+	operator: SExp,
+	expected: Type,
+	found:    Type,
+    },
+    InvalidArgList {
+	arglist:  SExp,
+	expected: Type,
+	found:    Type,
+    },
+    OtherError
+}
+
+impl SExp {
+    /// ```rust
+    /// use melisp::{
+    ///     r#type::{*, Type::*, TypeError::*},
+    ///     sexp::{SExp::*, SLeaf::*, util::*},
+    /// };
+    /// ```
+    pub fn type_check(&self) -> Result<Type, TypeError> {
+	todo!()
+    }
+}