Make compilation (--compile ...) works

lib/compiler.ml

@@ -0,0 +1,43 @@
+open Ppx_compare_lib.Builtin
+open Sexplib.Std
+
+type ocaml_type =
+    | Unspecified
+    | Int
+    | Float
+    | Bool
+    [@@deriving compare, sexp]
+
+type ocaml_expr =
+    | None_
+    | Int of int
+    | Bool of bool
+    | Symbol of {
+        name: string;
+        type_: ocaml_type;
+    }
+    | Let of {
+        rec_: bool;
+        name: string;
+        body: ocaml_expr list;
+        in_: ocaml_expr;
+    }
+    | Fun of {
+        params: ocaml_expr list;
+        body: ocaml_expr list;
+    }
+    [@@deriving compare, sexp]
+
+let compile node =
+    match node with
+    | Parser.Bool (value) -> Bool value
+    | Parser.Func (params, body) -> 0
+    | Parser.NumberInt (value) -> Int value
+    (* | Parser.NumberFloat (_) *)
+    (* | Parser.String_ (_) -> true *)
+    | _ -> failwith "compile unreachable code"
+let%test_unit "compile" =
+    ([%test_eq: ocaml_expr]
+        (compile (Parser.NumberInt 2))
+        (Int 2))
+

lib/dune

@@ -7,5 +7,5 @@
      ppx_assert
      ppx_compare
      ppx_sexp_conv))
- (modules Tokenizer Parser Evaluator)
+ (modules Tokenizer Parser Evaluator Compiler)
  (libraries str sexplib))