rename "unit" to "atom", to avoid confusion with the unit type;

--- a/src/Pure/Isar/outer_syntax.ML	Sun Aug 15 20:13:07 2010 +0200
+++ b/src/Pure/Isar/outer_syntax.ML	Sun Aug 15 20:19:56 2010 +0200
@@ -249,7 +249,7 @@
     handle ERROR msg => (Toplevel.malformed range_pos msg, true)
   end;
 
-fun prepare_unit commands init (cmd, proof, proper_proof) =
+fun prepare_atom commands init (cmd, proof, proper_proof) =
   let
     val (tr, proper_cmd) = prepare_span commands cmd |>> Toplevel.modify_init init;
     val proof_trs = map (prepare_span commands) proof |> filter #2 |> map #1;
@@ -278,14 +278,14 @@
     val toks = Source.exhausted (Thy_Syntax.token_source lexs pos (Source.of_string text));
     val spans = Source.exhaust (Thy_Syntax.span_source toks);
     val _ = List.app Thy_Syntax.report_span spans;  (* FIXME ?? *)
-    val units = Source.exhaust (Thy_Syntax.unit_source (Source.of_list spans))
-      |> Par_List.map (prepare_unit commands init) |> flat;
+    val atoms = Source.exhaust (Thy_Syntax.atom_source (Source.of_list spans))
+      |> Par_List.map (prepare_atom commands init) |> flat;
 
     val _ = Present.theory_source name
       (fn () => HTML.html_mode (implode o map Thy_Syntax.present_span) spans);
 
     val _ = if time then writeln ("\n**** Starting theory " ^ quote name ^ " ****") else ();
-    val (results, thy) = cond_timeit time "" (fn () => Toplevel.excursion units);
+    val (results, thy) = cond_timeit time "" (fn () => Toplevel.excursion atoms);
     val _ = if time then writeln ("**** Finished theory " ^ quote name ^ " ****\n") else ();
 
     fun after_load () =

--- a/src/Pure/Thy/thy_syntax.ML	Sun Aug 15 20:13:07 2010 +0200
+++ b/src/Pure/Thy/thy_syntax.ML	Sun Aug 15 20:19:56 2010 +0200
@@ -21,7 +21,7 @@
   val parse_spans: Scan.lexicon * Scan.lexicon -> Position.T -> string -> span list
   val present_span: span -> output
   val report_span: span -> unit
-  val unit_source: (span, 'a) Source.source ->
+  val atom_source: (span, 'a) Source.source ->
     (span * span list * bool, (span, 'a) Source.source) Source.source
 end;
 
@@ -160,7 +160,7 @@
 
 
 
-(** units: commands with proof **)
+(** specification atoms: commands with optional proof **)
 
 (* scanning spans *)
 
@@ -174,7 +174,7 @@
 val stopper = Scan.stopper (K eof) is_eof;
 
 
-(* unit_source *)
+(* atom_source *)
 
 local
 
@@ -188,13 +188,13 @@
     (if d = 0 then Scan.fail else command_with Keyword.is_qed >> pair (d - 1)) ||
     Scan.unless (command_with Keyword.is_theory) (Scan.one not_eof) >> pair d)) -- Scan.state);
 
-val unit =
+val atom =
   command_with Keyword.is_theory_goal -- proof >> (fn (a, (bs, d)) => (a, bs, d >= 0)) ||
   Scan.one not_eof >> (fn a => (a, [], true));
 
 in
 
-fun unit_source src = Source.source stopper (Scan.bulk unit) NONE src;
+fun atom_source src = Source.source stopper (Scan.bulk atom) NONE src;
 
 end;