diff --git a/erlang/apps/as/src/parse.erl b/erlang/apps/as/src/parse.erl
index f950a2b..9f7fd81 100644
--- a/erlang/apps/as/src/parse.erl
+++ b/erlang/apps/as/src/parse.erl
@@ -43,11 +43,11 @@ stmt(ScanState) ->
     {ok, {_Location, ?T_DOT_SUBSECTION}} -> dot_subsection(ScanState);
     {ok, {_Location, ?T_DOT_TEXT}} -> dot_text(ScanState);
     {ok, {_Location, ?T_DOT_TYPE}} -> dot_type(ScanState);
-    {ok, {_Location, {?T_SYMBOL, Name}}} -> stmt_after_symbol(ScanState, Name);
+    {ok, {Location, {?T_SYMBOL, Name}}} -> stmt_after_symbol(ScanState, Location, Name);
     {ok, {_Location, {?T_UINTEGER, UInt}}} -> stmt_after_uinteger(ScanState, UInt);
     {ok, {_Location, ?T_NEWLINE}} -> stmt(ScanState);
     {ok, {_Location, ?T_EOF}} -> eof;
-    ScanRes -> badtok(ScanState, "expected directive, label, or instruction", ScanRes)
+    ScanRes -> badtok("expected directive, label, or instruction", ScanRes)
   end.
 
 %% Instructions and labels -----------------------------------------------------
@@ -94,120 +94,120 @@ stmt(ScanState) ->
 %% This means that "opcode (...)" is interpreted as having a displacement but no
 %% index.  Use "opcode 0(index)" if an index with zero displacement is needed.
 
-stmt_after_symbol(ScanState, Name) ->
+stmt_after_symbol(ScanState, Location, Name) ->
   case scan:token(ScanState) of
     {ok, {_Location, ?T_COLON}} -> {ok, #s_label{name = Name}};
-    {ok, {_Location, ?T_NEWLINE}} -> make_insn(ScanState, Name, false, false, false, false);
-    {ok, {_Location, {?T_UINTEGER, UInt}}} -> insn_uint(ScanState, Name, UInt);
-    {ok, {_Location, {?T_SYMBOL, Symbol}}} -> insn_symbol(ScanState, Name, Symbol);
+    {ok, {_Location, ?T_NEWLINE}} -> make_insn(Location, Name, false, false, false, false);
+    {ok, {_Location, {?T_UINTEGER, UInt}}} -> insn_uint(ScanState, Location, Name, UInt);
+    {ok, {_Location, {?T_SYMBOL, Symbol}}} -> insn_symbol(ScanState, Location, Name, Symbol);
     {ok, {_Location, {?T_LOCAL_LABEL, Number, Direction}}} ->
-      insn_local_label(ScanState, Name, Number, Direction);
-    ScanRes -> badtok(ScanState, "junk after symbol", ScanRes)
+      insn_local_label(ScanState, Location, Name, Number, Direction);
+    ScanRes -> badtok("junk after symbol", ScanRes)
   end.
 
 %% <stmt> ::= <uinteger> . ":"
 stmt_after_uinteger(ScanState, UInt) ->
   case scan:token(ScanState) of
     {ok, {_Location, ?T_COLON}} -> {ok, #s_local_label{number = UInt}};
-    ScanRes -> badtok(ScanState, "junk after symbol", ScanRes)
+    ScanRes -> badtok("junk after symbol", ScanRes)
   end.
 
 %% Seen "<symbol> <uinteger>".  The <uinteger> is the <accumulator> if followed
 %% by ",", otherwise (the start of) the <displacement>.
-insn_uint(ScanState, Name, UInt) ->
+insn_uint(ScanState, Location, Name, UInt) ->
   case scan:token(ScanState) of
     {ok, {_Location, ?T_COMMA}} -> % the Uint is the Accumulator, parse EA next
-      insn_ea(ScanState, Name, _AccOrDev = UInt);
+      insn_ea(ScanState, Location, Name, _AccOrDev = UInt);
     {ok, {_Location, ?T_LPAREN}} -> % the Uint is the Displacement, parse Index next
       Displacement = #e_integer{value = UInt},
-      insn_ea_index(ScanState, Name, _AccOrDev = false, _At = false, Displacement);
+      insn_ea_index(ScanState, Location, Name, _AccOrDev = false, _At = false, Displacement);
     {ok, {_Location, ?T_NEWLINE}} -> % the Uint is the Displacement
       Displacement = #e_integer{value = UInt},
-      make_insn(ScanState, Name, _AccOrDev = false, _At = false, Displacement, _Index = false);
-    ScanRes -> badtok(ScanState, "junk after <symbol> <uinteger>", ScanRes)
+      make_insn(Location, Name, _AccOrDev = false, _At = false, Displacement, _Index = false);
+    ScanRes -> badtok("junk after <symbol> <uinteger>", ScanRes)
   end.
 
 %% Seen "<symbol> <symbol2>".  The <symbol2> is (the start of) the <displacement>.
 %% TODO: permit <symbol2> to be the <accumulator> (named register or device).
-insn_symbol(ScanState, Name, Symbol2) ->
+insn_symbol(ScanState, Location, Name, Symbol2) ->
   Displacement = #e_symbol{name = Symbol2},
-  insn_ea_disp(ScanState, Name, _AccOrDev = false, _At = false, Displacement).
+  insn_ea_disp(ScanState, Location, Name, _AccOrDev = false, _At = false, Displacement).
 
 %% Seen "<symbol> <local label>".  The <local label> is (the start of) the <displacement>.
-insn_local_label(ScanState, Name, Number, Direction) ->
+insn_local_label(ScanState, Location, Name, Number, Direction) ->
   Displacement = #e_local_label{number = Number, direction = Direction},
-  insn_ea_disp(ScanState, Name, _AccOrDev = false, _At = false, Displacement).
+  insn_ea_disp(ScanState, Location, Name, _AccOrDev = false, _At = false, Displacement).
 
 %% <symbol> <accordev> "," . [ ["@"] <displacement> ["(" <index> ")"] ] <newline>
-insn_ea(ScanState, Name, AccOrDev) ->
+insn_ea(ScanState, Location, Name, AccOrDev) ->
   case scan:token(ScanState) of
     {ok, {_Location, ?T_NEWLINE}} ->
-      make_insn(ScanState, Name, AccOrDev, _At = false, _Displacement = false, _Index = false);
-    {ok, {_Location, ?T_AT}} -> insn_ea_at(ScanState, Name, AccOrDev);
+      make_insn(Location, Name, AccOrDev, _At = false, _Displacement = false, _Index = false);
+    {ok, {_Location, ?T_AT}} -> insn_ea_at(ScanState, Location, Name, AccOrDev);
     {ok, {_Lcation, {?T_UINTEGER, UInt}}} ->
       Displacement = #e_integer{value = UInt},
-      insn_ea_disp(ScanState, Name, AccOrDev, _At = false, Displacement);
+      insn_ea_disp(ScanState, Location, Name, AccOrDev, _At = false, Displacement);
     {ok, {_Location, {?T_SYMBOL, Symbol}}} ->
       Displacement = #e_symbol{name = Symbol},
-      insn_ea_disp(ScanState, Name, AccOrDev, _At = false, Displacement);
+      insn_ea_disp(ScanState, Location, Name, AccOrDev, _At = false, Displacement);
     {ok, {_Location, {?T_LOCAL_LABEL, Number, Direction}}} ->
       Displacement = #e_local_label{number = Number, direction = Direction},
-      insn_ea_disp(ScanState, Name, AccOrDev, _At = false, Displacement);
-    ScanRes -> badtok(ScanState, "junk after comma", ScanRes)
+      insn_ea_disp(ScanState, Location, Name, AccOrDev, _At = false, Displacement);
+    ScanRes -> badtok("junk after comma", ScanRes)
   end.
 
 %% <symbol> [<accordev> ","] "@" . <displacement> ["(" <index> ")"] <newline>
-insn_ea_at(ScanState, Name, AccOrDev) ->
+insn_ea_at(ScanState, Location, Name, AccOrDev) ->
   case scan:token(ScanState) of
     {ok, {_Location, {?T_UINTEGER, UInt}}} ->
       Displacement = #e_integer{value = UInt},
-      insn_ea_disp(ScanState, Name, AccOrDev, _At = true, Displacement);
+      insn_ea_disp(ScanState, Location, Name, AccOrDev, _At = true, Displacement);
     {ok, {_Location, {?T_SYMBOL, Symbol}}} ->
       Displacement = #e_symbol{name = Symbol},
-      insn_ea_disp(ScanState, Name, AccOrDev, _At = true, Displacement);
+      insn_ea_disp(ScanState, Location, Name, AccOrDev, _At = true, Displacement);
     {ok, {_Location, {?T_LOCAL_LABEL, Number, Direction}}} ->
       Displacement = #e_local_label{number = Number, direction = Direction},
-      insn_ea_disp(ScanState, Name, AccOrDev, _At = true, Displacement);
-    ScanRes -> badtok(ScanState, "junk after @", ScanRes)
+      insn_ea_disp(ScanState, Location, Name, AccOrDev, _At = true, Displacement);
+    ScanRes -> badtok("junk after @", ScanRes)
   end.
 
 %% <symbol> [<accordev> ","] ["@"] <displacement> . ["(" <index> ")"] <newline>
-insn_ea_disp(ScanState, Name, AccOrDev, At, Displacement) ->
+insn_ea_disp(ScanState, Location, Name, AccOrDev, At, Displacement) ->
   case scan:token(ScanState) of
-    {ok, {_Location, ?T_LPAREN}} -> insn_ea_index(ScanState, Name, AccOrDev, At, Displacement);
-    {ok, {_Location, ?T_NEWLINE}} -> make_insn(ScanState, Name, AccOrDev, At, Displacement, _Index = false);
-    ScanRes -> badtok(ScanState, "junk after <displacement>", ScanRes)
+    {ok, {_Location, ?T_LPAREN}} -> insn_ea_index(ScanState, Location, Name, AccOrDev, At, Displacement);
+    {ok, {_Location, ?T_NEWLINE}} -> make_insn(Location, Name, AccOrDev, At, Displacement, _Index = false);
+    ScanRes -> badtok("junk after <displacement>", ScanRes)
   end.
 
 %% <symbol> [<accordev> ","] ["@"] <displacement> "(" . <index> ")" <newline>
-insn_ea_index(ScanState, Name, AccOrDev, At, Displacement) ->
+insn_ea_index(ScanState, Location, Name, AccOrDev, At, Displacement) ->
   case scan:token(ScanState) of
     {ok, {_Location1, {?T_UINTEGER, Index}}} when Index =< 8#17 ->
       case scan:token(ScanState) of
         {ok, {_Location2, ?T_RPAREN}} ->
           case scan:token(ScanState) of
             {ok, {_Location3, ?T_NEWLINE}} ->
-              make_insn(ScanState, Name, AccOrDev, At, Displacement, Index);
-            ScanRes -> badtok(ScanState, "junk after <index>", ScanRes)
+              make_insn(Location, Name, AccOrDev, At, Displacement, Index);
+            ScanRes -> badtok("junk after <index>", ScanRes)
           end;
-        ScanRes -> badtok(ScanState, "junk in <index>", ScanRes)
+        ScanRes -> badtok("junk in <index>", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk in <index>", ScanRes)
+    ScanRes -> badtok("junk in <index>", ScanRes)
   end.
 
-make_insn(ScanState, Name, AccOrDev, At, Displacement, Index) ->
+make_insn(Location, Name, AccOrDev, At, Displacement, Index) ->
   Models = ?PDP10_KL10_271, % FIXME: make dynamic
   case pdp10_opcodes:insn_from_name(Models, Name, AccOrDev =/= false) of
-    false -> badinsn(ScanState, "invalid mnemonic ~s", Name);
+    false -> badinsn(Location, "invalid mnemonic ~s", Name);
     #pdp10_insn_desc{ high13 = High13
                     , format = Format
                     , e_unused = EUnused
                     , extended = false % TODO: handle extended opcodes
                     } ->
-      case make_high13(ScanState, Name, AccOrDev, High13, Format) of
+      case make_high13(Location, Name, AccOrDev, High13, Format) of
         {error, _Reason} = Error -> Error;
         {ok, FinalHigh13} ->
-          case check_e(ScanState, Name, At, Displacement, Index, EUnused) of
+          case check_e(Location, Name, At, Displacement, Index, EUnused) of
             {error, _Reason} = Error -> Error;
             ok -> {ok, #s_insn{ high13 = FinalHigh13
                               , at = At
@@ -221,14 +221,14 @@ make_insn(ScanState, Name, AccOrDev, At, Displacement, Index) ->
       end
   end.
 
-make_high13(ScanState, Name, AccOrDev, High13, Format) ->
+make_high13(Location, Name, AccOrDev, High13, Format) ->
   case {Format, AccOrDev} of
     {?PDP10_INSN_A_OPCODE, false} ->
       {ok, High13};
     {?PDP10_INSN_A_OPCODE, _} ->
-      badinsn(ScanState, "~s: extraneous accumulator operand", Name);
+      badinsn(Location, "~s: extraneous accumulator operand", Name);
     {?PDP10_INSN_IO, false} ->
-      badinsn(ScanState, "~s: missing device operand", Name);
+      badinsn(Location, "~s: missing device operand", Name);
     {?PDP10_INSN_IO, _} ->
       make_high13_io(High13, AccOrDev);
     {?PDP10_INSN_BASIC, false} ->
@@ -236,9 +236,9 @@ make_high13(ScanState, Name, AccOrDev, High13, Format) ->
     {?PDP10_INSN_BASIC, _} ->
       make_high13_basic(High13, AccOrDev);
     {?PDP10_INSN_A_NONZERO, false} ->
-      badinsn(ScanState, "~s: missing accumulator operand", Name);
+      badinsn(Location, "~s: missing accumulator operand", Name);
     {?PDP10_INSN_A_NONZERO, 0} ->
-      badinsn(ScanState, "~s: accumulator must not be zero", Name);
+      badinsn(Location, "~s: accumulator must not be zero", Name);
     {?PDP10_INSN_A_NONZERO, _} ->
       make_high13_basic(High13, AccOrDev)
   end.
@@ -251,17 +251,17 @@ make_high13_io(High13, Device) ->
   Mask = ((1 bsl 7) - 1),
   {ok, (High13 band bnot (Mask bsl 3)) bor ((Device band Mask) bsl 3)}.
 
-check_e(ScanState, Name, At, Displacement, Index, EUnused) ->
+check_e(Location, Name, At, Displacement, Index, EUnused) ->
   HaveE = At orelse Displacement =/= false orelse Index =/= false,
   case {EUnused, HaveE} of
     {true, false} -> ok;
-    {true, true} -> badinsn(ScanState, "~s: extraneous address operand", Name);
-    {false, false} -> badinsn(ScanState, "~s: missing address operand", Name);
+    {true, true} -> badinsn(Location, "~s: extraneous address operand", Name);
+    {false, false} -> badinsn(Location, "~s: missing address operand", Name);
     {false, true} -> ok
   end.
 
-badinsn(ScanState, Fmt, Mnemonic) ->
-  fmterr(ScanState, Fmt, [Mnemonic]).
+badinsn(Location, Fmt, Mnemonic) ->
+  fmterr(Location, Fmt, [Mnemonic]).
 
 %% Directives ------------------------------------------------------------------
 
@@ -271,9 +271,9 @@ dot_data(ScanState) ->
     {ok, {_Location1, {?T_UINTEGER, Nr}}} ->
       case scan:token(ScanState) of
         {ok, {_Location2, ?T_NEWLINE}} -> {ok, #s_dot_data{nr = Nr}};
-        ScanRes -> badtok(ScanState, "junk after .data <nr>", ScanRes)
+        ScanRes -> badtok("junk after .data <nr>", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .data", ScanRes)
+    ScanRes -> badtok("junk after .data", ScanRes)
   end.
 
 dot_file(ScanState) ->
@@ -289,9 +289,9 @@ dot_file_or_ident(ScanState, MkStmt, ErrMsg) ->
     {ok, {_Location1, {?T_STRING, String}}} ->
       case scan:token(ScanState) of
         {ok, {_Location2, ?T_NEWLINE}} -> {ok, MkStmt(String)};
-        ScanRes -> badtok(ScanState, ErrMsg, ScanRes)
+        ScanRes -> badtok(ErrMsg, ScanRes)
       end;
-    ScanRes -> badtok(ScanState, ErrMsg, ScanRes)
+    ScanRes -> badtok(ErrMsg, ScanRes)
   end.
 
 dot_globl(ScanState) ->
@@ -299,21 +299,21 @@ dot_globl(ScanState) ->
     {ok, {_Location1, {?T_SYMBOL, Name}}} ->
       case scan:token(ScanState) of
         {ok, {_Location2, ?T_NEWLINE}} -> {ok, #s_dot_globl{name = Name}};
-        ScanRes -> badtok(ScanState, "junk after .globl", ScanRes)
+        ScanRes -> badtok("junk after .globl", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .globl", ScanRes)
+    ScanRes -> badtok("junk after .globl", ScanRes)
   end.
 
 dot_popsection(ScanState) ->
   case scan:token(ScanState) of
     {ok, {_Location, ?T_NEWLINE}} -> {ok, #s_dot_popsection{}};
-    ScanRes -> badtok(ScanState, "junk after .popsection", ScanRes)
+    ScanRes -> badtok("junk after .popsection", ScanRes)
   end.
 
 dot_previous(ScanState) ->
   case scan:token(ScanState) of
     {ok, {_Location, ?T_NEWLINE}} -> {ok, #s_dot_previous{}};
-    ScanRes -> badtok(ScanState, "junk after .previous", ScanRes)
+    ScanRes -> badtok("junk after .previous", ScanRes)
   end.
 
 %% For now only accepts ".pushsection <name> [, <nr>]".  TODO: extend
@@ -324,7 +324,7 @@ dot_pushsection(ScanState) ->
     %% TODO: do we need a general mapping from reserved to plain symbols?
     {ok, {_Location, ?T_DOT_DATA}} -> dot_pushsection(ScanState, _Name = ".data");
     {ok, {_Location, ?T_DOT_TEXT}} -> dot_pushsection(ScanState, _Name = ".text");
-    ScanRes -> badtok(ScanState, "junk after .pushsection", ScanRes)
+    ScanRes -> badtok("junk after .pushsection", ScanRes)
   end.
 
 %% Seen ".pushsection <name>", expects "[, <nr>]".
@@ -336,11 +336,11 @@ dot_pushsection(ScanState, Name) ->
         {ok, {_Location2, {?T_UINTEGER, Nr}}} ->
           case scan:token(ScanState) of
             {ok, {_Location3, ?T_NEWLINE}} -> {ok, #s_dot_pushsection{name = Name, nr = Nr}};
-            ScanRes -> badtok(ScanState, "junk after .pushsection <name>, <nr>", ScanRes)
+            ScanRes -> badtok("junk after .pushsection <name>, <nr>", ScanRes)
           end;
-        ScanRes -> badtok(ScanState, "junk after .pushsection <name>,", ScanRes)
+        ScanRes -> badtok("junk after .pushsection <name>,", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .pushsection <name>", ScanRes)
+    ScanRes -> badtok("junk after .pushsection <name>", ScanRes)
   end.
 
 %% For now only accepts ".size <sym>,.-<sym>".  TODO: extend
@@ -357,17 +357,17 @@ dot_size(ScanState) ->
                     {ok, {_Location5, {?T_SYMBOL, Name}}} -> % same Name as above
                       case scan:token(ScanState) of
                         {ok, {_Location6, ?T_NEWLINE}} -> {ok, #s_dot_size{name = Name}};
-                        ScanRes -> badtok(ScanState, "junk after .size", ScanRes)
+                        ScanRes -> badtok("junk after .size", ScanRes)
                       end;
-                    ScanRes -> badtok(ScanState, "junk after .size", ScanRes)
+                    ScanRes -> badtok("junk after .size", ScanRes)
                   end;
-                ScanRes -> badtok(ScanState, "junk after .size", ScanRes)
+                ScanRes -> badtok("junk after .size", ScanRes)
               end;
-            ScanRes -> badtok(ScanState, "junk after .size", ScanRes)
+            ScanRes -> badtok("junk after .size", ScanRes)
           end;
-        ScanRes -> badtok(ScanState, "junk after .size", ScanRes)
+        ScanRes -> badtok("junk after .size", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .size", ScanRes)
+    ScanRes -> badtok("junk after .size", ScanRes)
   end.
 
 dot_subsection(ScanState) ->
@@ -375,9 +375,9 @@ dot_subsection(ScanState) ->
     {ok, {_Location1, {?T_UINTEGER, Nr}}} ->
       case scan:token(ScanState) of
         {ok, {_Location2, ?T_NEWLINE}} -> {ok, #s_dot_subsection{nr = Nr}};
-        ScanRes -> badtok(ScanState, "junk after .subsection <nr>", ScanRes)
+        ScanRes -> badtok("junk after .subsection <nr>", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .subsection", ScanRes)
+    ScanRes -> badtok("junk after .subsection", ScanRes)
   end.
 
 dot_text(ScanState) ->
@@ -386,9 +386,9 @@ dot_text(ScanState) ->
     {ok, {_Location1, {?T_UINTEGER, Nr}}} ->
       case scan:token(ScanState) of
         {ok, {_Location2, ?T_NEWLINE}} -> {ok, #s_dot_text{nr = Nr}};
-        ScanRes -> badtok(ScanState, "junk after .text <nr>", ScanRes)
+        ScanRes -> badtok("junk after .text <nr>", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .text", ScanRes)
+    ScanRes -> badtok("junk after .text", ScanRes)
   end.
 
 %% For now only accepts ".type <sym>,@function".  TODO: extend
@@ -403,25 +403,24 @@ dot_type(ScanState) ->
                 {ok, {_Location4, {?T_SYMBOL, "function"}}} ->
                   case scan:token(ScanState) of
                     {ok, {_Location5, ?T_NEWLINE}} -> {ok, #s_dot_type{name = Name}};
-                    ScanRes -> badtok(ScanState, "junk after .type", ScanRes)
+                    ScanRes -> badtok("junk after .type", ScanRes)
                   end;
-                ScanRes -> badtok(ScanState, "junk after .type", ScanRes)
+                ScanRes -> badtok("junk after .type", ScanRes)
               end;
-            ScanRes -> badtok(ScanState, "junk after .type", ScanRes)
+            ScanRes -> badtok("junk after .type", ScanRes)
           end;
-        ScanRes -> badtok(ScanState, "junk after .type", ScanRes)
+        ScanRes -> badtok("junk after .type", ScanRes)
       end;
-    ScanRes -> badtok(ScanState, "junk after .type", ScanRes)
+    ScanRes -> badtok("junk after .type", ScanRes)
   end.
 
 %% Error reporting -------------------------------------------------------------
 
-badtok(_ScanState, _ErrMsg, {error, _Reason} = Error) -> Error;
-badtok(ScanState, ErrMsg, {ok, {_Location, Token}}) ->
-  fmterr(ScanState, ErrMsg ++ "; current token is ~s", [token:format(Token)]).
+badtok(_ErrMsg, {error, _Reason} = Error) -> Error;
+badtok(ErrMsg, {ok, {Location, Token}}) ->
+  fmterr(Location, ErrMsg ++ "; current token is ~s", [token:format(Token)]).
 
-fmterr(ScanState, Fmt, Args) ->
-  {ok, {FileName, LineNr}} = scan_state:location(ScanState),
+fmterr({FileName, LineNr}, Fmt, Args) ->
   {error, {?MODULE, {FileName, LineNr, Fmt, Args}}}.
 
 -spec format_error(term()) -> io_lib:chars().