ast: improved the implementation of syntactic_ast

debug: added debug functions for the syntactic_ast module
Modified the compiler executable to test a little bit.

todo: Some nodes of the syntactic ast are not yet emitted,

lib/compiler/syntactic_ast.mli

@@ -0,0 +1,37 @@
+type symbol = string
+(* These are just used for the GADT *)
+type expression
+type definition
+type clause (* for cond *)
+type binding (* for let *)
+type lambda_list
+
+type _ t =
+  | LitInt : int -> expression t
+  | LitDouble : float -> expression t
+  | LitString : string -> expression t
+  | LitNil : expression t
+  | QuotedList : expression t list * expression t option -> expression t
+  | LambdaList : symbol list * symbol option -> lambda_list t
+  | Lambda : lambda_list t * definition t list * expression t list -> expression t
+  | Define : symbol * expression t -> definition t
+
+  | LetBinding : symbol * expression t -> binding t
+  | Let : binding t list * expression t list -> expression t
+
+  | CondClause : expression t * expression t -> clause t
+  | Cond : clause t list -> expression t
+
+  | Var : symbol -> expression t
+  | Apply : expression t * expression t list -> expression t
+
+type top_level =
+  | Def of definition t
+  | Exp of expression t
+
+
+val make : Parser.Ast.lisp_ast -> (top_level, string) result
+
+val print_def : definition t -> string
+val print_expr : expression t -> string
+val print : top_level -> string