Add file for AST

ast.rkt

@@ -0,0 +1,19 @@
+#lang typed/racket
+
+(define-type ConId Integer)
+(define-type Arity Integer)
+(define-type Let (∪ 'let 'letrec))
+(define-type Name Symbol)
+
+
+(define-type (Bind A) (List A (Expr A)))
+(define-type (Alt A) (List 'branch ConId (Listof A) (Expr A)))
+
+(define-type (Expr A)
+  (∪ Name
+     Integer
+     (List 'pack ConId Arity)
+     (List (Expr A) (Expr A))
+     (List Let (Pair (Bind A) (Listof (Bind A))) (Expr A))
+     (List 'case (Expr A) (Pair (Alt A) (Listof (Alt A))))
+     (List 'λ (Pair Name (Listof Name)) (Expr A))))