Add locations and improve error messages and improve code quality

bin/sgen.ml

@@ -2,54 +2,52 @@ open Base
 open Cmdliner
 open Stellogen
 
+let create_start_pos filename =
+  { Lexing.pos_fname = filename; pos_lnum = 1; pos_bol = 0; pos_cnum = 0 }
+
 let parse input_file =
   let lexbuf = Sedlexing.Utf8.from_channel (Stdlib.open_in input_file) in
-  let start_pos filename =
-    { Lexing.pos_fname = filename; pos_lnum = 1; pos_bol = 0; pos_cnum = 0 }
-  in
-  Sedlexing.set_position lexbuf (start_pos input_file);
+  Sedlexing.set_position lexbuf (create_start_pos input_file);
   Sgen_parsing.parse_with_error input_file lexbuf
 
 let run input_file =
   let expr = parse input_file in
   let preprocessed = Expr.preprocess expr in
   match Expr.program_of_expr preprocessed with
-  | Ok p ->
-    let _ = Stellogen.Sgen_eval.eval_program p in
+  | Ok program ->
+    let (_ : (Sgen_ast.env, Sgen_ast.err) Result.t) =
+      Sgen_eval.eval_program program
+    in
     ()
-  | Error e ->
-    let open Stellogen.Sgen_eval in
-    begin
-      match pp_err (ExprError e) with
-      | Ok pp ->
-        Out_channel.output_string Out_channel.stderr pp;
-        ()
-      | Error _ -> ()
-    end
+  | Error expr_error -> (
+    match Sgen_eval.pp_err (ExprError (expr_error, None)) with
+    | Ok error_msg -> Stdlib.Printf.eprintf "%s" error_msg
+    | Error _ -> () )
 
 let preprocess_only input_file =
   let expr = parse input_file in
   let preprocessed = Expr.preprocess expr in
-  Stdlib.print_string
-    (List.map ~f:Expr.to_string preprocessed |> String.concat ~sep:"\n");
-  Stdlib.print_newline ()
+  preprocessed |> List.map ~f:Expr.to_string |> String.concat ~sep:"\n"
+  |> Stdlib.print_endline
 
 let input_file_arg =
   let doc = "Input file to process." in
   Arg.(required & pos 0 (some string) None & info [] ~docv:"FILENAME" ~doc)
 
 let wrap f input_file =
-  try Ok (f input_file) with e -> Error (`Msg (Stdlib.Printexc.to_string e))
+  try Ok (f input_file) with e -> Error (`Msg (Exn.to_string e))
 
 let run_cmd =
+  let doc = "Run the Stellogen program" in
   let term = Term.(const (wrap run) $ input_file_arg |> term_result) in
-  Cmd.v (Cmd.info "run" ~doc:"Run the Stellogen program") term
+  Cmd.v (Cmd.info "run" ~doc) term
 
 let preprocess_cmd =
+  let doc = "Show the preprocessed code" in
   let term =
     Term.(const (wrap preprocess_only) $ input_file_arg |> term_result)
   in
-  Cmd.v (Cmd.info "preprocess" ~doc:"Show the preprocessed code") term
+  Cmd.v (Cmd.info "preprocess" ~doc) term
 
 let default_cmd =
   let doc = "Stellogen: code generator and evaluator" in