+ class Symbol
+ property :str
+
+ def initialize(@str : String)
+ end
+
+ def ==(other : Symbol)
+ @str == other.str
+ end
+ end
+
+ class List < Array(Type)
+ end
+
+ class Vector < Array(Type)
+ end
+
+ class HashMap < Hash(String, Type)
+ end
+
+ class Atom
+ property :val
+
+ def initialize(@val : Type)
+ end
+
+ def ==(rhs : Atom)
+ @val == rhs.val
+ end
+ end
+
+ class Closure
+ property :ast, :params, :env, :fn
+
+ def initialize(@ast : Type, @params : Array(Mal::Type) | List | Vector, @env : Env, @fn : Func)
+ end
+ end
+
+ alias Type::ValueType = Nil | Bool | Int64 | String | Symbol | List | Vector | HashMap | Func | Closure | Atom