freepascal.compiler/compiler/htypechk.pas

{
    $Id$
    Copyright (c) 1996-98 by Florian Klaempfl

    This unit exports some help routines for the type checking

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 ****************************************************************************
}
unit htypechk;
interface

    uses
      tree,symtable;

    const
    { firstcallparan without varspez we don't count the ref }
       count_ref : boolean = true;
       allow_array_constructor : boolean = false;


    { Conversion }
    function isconvertable(def_from,def_to : pdef;
             var doconv : tconverttype;fromtreetype : ttreetyp;
             explicit : boolean) : boolean;

    { Register Allocation }
    procedure make_not_regable(p : ptree);
    procedure left_right_max(p : ptree);
    procedure calcregisters(p : ptree;r32,fpu,mmx : word);

    { subroutine handling }
    procedure test_protected_sym(sym : psym);
    procedure test_protected(p : ptree);
    function  is_procsym_load(p:Ptree):boolean;
    function  is_procsym_call(p:Ptree):boolean;
    function  is_assignment_overloaded(from_def,to_def : pdef) : boolean;


implementation

    uses
       cobjects,verbose,systems,globals,
       aasm,types,
       hcodegen;

{****************************************************************************
                             Convert
****************************************************************************}

    function isconvertable(def_from,def_to : pdef;
             var doconv : tconverttype;fromtreetype : ttreetyp;
             explicit : boolean) : boolean;
{$ifndef OLDCNV}
      { Tbasetype:  uauto,uvoid,uchar,
                    u8bit,u16bit,u32bit,
                    s8bit,s16bit,s32,
                    bool8bit,bool16bit,boot32bit }
      type
        tbasedef=(bvoid,bchar,bint,bbool);
      const
        basedeftbl:array[tbasetype] of tbasedef =
          (bvoid,bvoid,bchar,
           bint,bint,bint,
           bint,bint,bint,
           bbool,bbool,bbool);
        basedefconverts : array[tbasedef,tbasedef] of tconverttype =
         ((tc_not_possible,tc_not_possible,tc_not_possible,tc_not_possible),
          (tc_not_possible,tc_equal,tc_not_possible,tc_not_possible),
          (tc_not_possible,tc_not_possible,tc_int_2_int,tc_int_2_bool),
          (tc_not_possible,tc_not_possible,tc_bool_2_int,tc_int_2_bool));
{$else}
      const
         basedefconverts : array[tbasetype,tbasetype] of tconverttype =
           {uauto}
           ((tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible),
           {uvoid}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible),
           {uchar}
            (tc_not_possible,tc_not_possible,tc_only_rangechecks32bit,
             tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible,
             tc_not_possible,tc_not_possible,tc_not_possible),
           {u8bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_only_rangechecks32bit,tc_u8bit_2_u16bit,tc_u8bit_2_u32bit,
             tc_only_rangechecks32bit,tc_u8bit_2_s16bit,tc_u8bit_2_s32bit,
             tc_int_2_bool,tc_int_2_bool,tc_int_2_bool),
           {u16bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_u16bit_2_u8bit,tc_only_rangechecks32bit,tc_u16bit_2_u32bit,
             tc_u16bit_2_s8bit,tc_only_rangechecks32bit,tc_u16bit_2_s32bit,
             tc_int_2_bool,tc_int_2_bool,tc_int_2_bool),
           {u32bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_u32bit_2_u8bit,tc_u32bit_2_u16bit,tc_only_rangechecks32bit,
             tc_u32bit_2_s8bit,tc_u32bit_2_s16bit,tc_only_rangechecks32bit,
             tc_int_2_bool,tc_int_2_bool,tc_int_2_bool),
           {s8bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_only_rangechecks32bit,tc_s8bit_2_u16bit,tc_s8bit_2_u32bit,
             tc_only_rangechecks32bit,tc_s8bit_2_s16bit,tc_s8bit_2_s32bit,
             tc_int_2_bool,tc_int_2_bool,tc_int_2_bool),
           {s16bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_s16bit_2_u8bit,tc_only_rangechecks32bit,tc_s16bit_2_u32bit,
             tc_s16bit_2_s8bit,tc_only_rangechecks32bit,tc_s16bit_2_s32bit,
             tc_int_2_bool,tc_int_2_bool,tc_int_2_bool),
           {s32bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_s32bit_2_u8bit,tc_s32bit_2_u16bit,tc_only_rangechecks32bit,
             tc_s32bit_2_s8bit,tc_s32bit_2_s16bit,tc_only_rangechecks32bit,
             tc_int_2_bool,tc_int_2_bool,tc_int_2_bool),
           {bool8bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_bool_2_int,tc_bool_2_int,tc_bool_2_int,
             tc_bool_2_int,tc_bool_2_int,tc_bool_2_int,
             tc_only_rangechecks32bit,tc_int_2_bool,tc_int_2_bool),
           {bool16bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_bool_2_int,tc_bool_2_int,tc_bool_2_int,
             tc_bool_2_int,tc_bool_2_int,tc_bool_2_int,
             tc_int_2_bool,tc_only_rangechecks32bit,tc_int_2_bool),
           {bool32bit}
            (tc_not_possible,tc_not_possible,tc_not_possible,
             tc_bool_2_int,tc_bool_2_int,tc_bool_2_int,
             tc_bool_2_int,tc_bool_2_int,tc_bool_2_int,
             tc_int_2_bool,tc_int_2_bool,tc_only_rangechecks32bit));
{$endif}

      var
         b : boolean;
         hd1,hd2 : pdef;
      begin
       { safety check }
         if not(assigned(def_from) and assigned(def_to)) then
          begin
            isconvertable:=false;
            exit;
          end;

         b:=false;
       { we walk the wanted (def_to) types and check then the def_from
         types if there is a conversion possible }
         case def_to^.deftype of
           orddef :
             begin
               case def_from^.deftype of
                 orddef :
                   begin
{$ifndef OLDCNV}
                     doconv:=basedefconverts[basedeftbl[porddef(def_from)^.typ],basedeftbl[porddef(def_to)^.typ]];
                     b:=true;
                     if (doconv=tc_not_possible) or
                        ((doconv=tc_int_2_bool) and
                         (not explicit) and
                         (not is_boolean(def_from))) then
                       b:=false;
{$else}
                     doconv:=basedefconverts[porddef(def_from)^.typ,porddef(def_to)^.typ];
                     b:=true;
                     if (doconv=tc_not_possible) or
                        ((doconv=tc_int_2_bool) and
                         (not explicit) and
                         (not is_boolean(def_from))) then
                       b:=false;
{$endif}
                   end;
{$ifndef OLDCNV}
                 enumdef :
                   begin
                     doconv:=tc_int_2_int;
                     b:=true;
                   end;
{$endif}
               end;
             end;

          stringdef :
             begin
               case def_from^.deftype of
                stringdef : begin
                              doconv:=tc_string_2_string;
                              b:=true;
                            end;
                   orddef : begin
                            { char to string}
                              if is_char(def_from) then
                               begin
                                 doconv:=tc_char_2_string;
                                 b:=true;
                               end;
                            end;
                 arraydef : begin
                            { string to array of char, the length check is done by the firstpass of this node }
                              if is_equal(parraydef(def_from)^.definition,cchardef) then
                               begin
                                 doconv:=tc_chararray_2_string;
                                 b:=true;
                               end;
                            end;
               pointerdef : begin
                            { pchar can be assigned to short/ansistrings }
                              if is_pchar(def_from) then
                               begin
                                 doconv:=tc_pchar_2_string;
                                 b:=true;
                               end;
                            end;
               end;
             end;

           floatdef :
             begin
               case def_from^.deftype of
                orddef : begin { ordinal to real }
                           if pfloatdef(def_to)^.typ=f32bit then
                            doconv:=tc_int_2_fix
                           else
                            doconv:=tc_int_2_real;
                           b:=true;
                         end;
              floatdef : begin { 2 float types ? }
                           if pfloatdef(def_from)^.typ=pfloatdef(def_to)^.typ then
                             doconv:=tc_equal
                           else
                             begin
                                if pfloatdef(def_from)^.typ=f32bit then
                                  doconv:=tc_fix_2_real
                                else
                                  if pfloatdef(def_to)^.typ=f32bit then
                                    doconv:=tc_real_2_fix
                                  else
                                    doconv:=tc_real_2_real;
                                { comp isn't a floating type }
{$ifdef i386}
                                if (pfloatdef(def_to)^.typ=s64bit) and
                                   (pfloatdef(def_from)^.typ<>s64bit) and
                                   not (explicit) then
                                  CGMessage(type_w_convert_real_2_comp);
{$endif}
                             end;
                           b:=true;
                         end;
               end;
             end;

           enumdef :
             begin
               if (def_from^.deftype=enumdef) then
                begin
                  if assigned(penumdef(def_from)^.basedef) then
                   hd1:=penumdef(def_from)^.basedef
                  else
                   hd1:=def_from;
                  if assigned(penumdef(def_to)^.basedef) then
                   hd2:=penumdef(def_to)^.basedef
                  else
                   hd2:=def_to;
                  b:=(hd1=hd2);
                end;
             end;

           arraydef :
             begin
             { open array is also compatible with a single element of its base type }
               if is_open_array(def_to) and
                  is_equal(parraydef(def_to)^.definition,def_from) then
                begin
                  doconv:=tc_equal;
                  b:=true;
                end
               else
                begin
                  case def_from^.deftype of
                   pointerdef : begin
                                  if (parraydef(def_to)^.lowrange=0) and
                                     is_equal(ppointerdef(def_from)^.definition,parraydef(def_to)^.definition) then
                                   begin
                                     doconv:=tc_pointer_2_array;
                                     b:=true;
                                   end;
                                end;
                    stringdef : begin
                                  { array of char to string }
                                  if is_equal(parraydef(def_to)^.definition,cchardef) then
                                   begin
                                     doconv:=tc_string_2_chararray;
                                     b:=true;
                                   end;
                                end;
                  end;
                end;
             end;

           pointerdef :
             begin
               case def_from^.deftype of
               stringdef : begin
                             { string constant to zero terminated string constant }
                             if (fromtreetype=stringconstn) and
                                is_pchar(def_to) then
                              begin
                                doconv:=tc_cstring_2_pchar;
                                b:=true;
                              end;
                           end;
                  orddef : begin
                             { char constant to zero terminated string constant }
                             if (fromtreetype=ordconstn) and is_equal(def_from,cchardef) and
                                is_pchar(def_to) then
                              begin
                                doconv:=tc_cchar_2_pchar;
                                b:=true;
                              end;
                           end;
                arraydef : begin
                             { chararray to pointer }
                             if (parraydef(def_from)^.lowrange=0) and
                                is_equal(parraydef(def_from)^.definition,ppointerdef(def_to)^.definition) then
                              begin
                                doconv:=tc_array_2_pointer;
                                b:=true;
                              end;
                           end;
              pointerdef : begin
                             { child class pointer can be assigned to anchestor pointers }
                             if (
                                 (ppointerdef(def_from)^.definition^.deftype=objectdef) and
                                 (ppointerdef(def_to)^.definition^.deftype=objectdef) and
                                 pobjectdef(ppointerdef(def_from)^.definition)^.isrelated(
                                   pobjectdef(ppointerdef(def_to)^.definition))
                                ) or
                                { all pointers can be assigned to void-pointer }
                                is_equal(ppointerdef(def_to)^.definition,voiddef) or
                                { in my opnion, is this not clean pascal }
                                { well, but it's handy to use, it isn't ? (FK) }
                                is_equal(ppointerdef(def_from)^.definition,voiddef) then
                               begin
                                 doconv:=tc_equal;
                                 b:=true;
                               end;
                           end;
              procvardef : begin
                             { procedure variable can be assigned to an void pointer }
                             { Not anymore. Use the @ operator now.}
                             if not(m_tp_procvar in aktmodeswitches) and
                                (ppointerdef(def_to)^.definition^.deftype=orddef) and
                                (porddef(ppointerdef(def_to)^.definition)^.typ=uvoid) then
                              begin
                                doconv:=tc_equal;
                                b:=true;
                              end;
                           end;
             classrefdef,
               objectdef : begin
                             { class types and class reference type
                               can be assigned to void pointers      }
                             if (
                                 ((def_from^.deftype=objectdef) and pobjectdef(def_from)^.isclass) or
                                 (def_from^.deftype=classrefdef)
                                ) and
                                (ppointerdef(def_to)^.definition^.deftype=orddef) and
                                (porddef(ppointerdef(def_to)^.definition)^.typ=uvoid) then
                               begin
                                 doconv:=tc_equal;
                                 b:=true;
                               end;
                           end;
               end;
             end;

           setdef :
             begin
               { automatic arrayconstructor -> set conversion }
               if (def_from^.deftype=arraydef) and (parraydef(def_from)^.IsConstructor) then
                begin
                  doconv:=tc_arrayconstructor_2_set;
                  b:=true;
                end;
             end;

           procvardef :
             begin
               { proc -> procvar }
               if (def_from^.deftype=procdef) then
                begin
                  def_from^.deftype:=procvardef;
                  doconv:=tc_proc_2_procvar;
                  b:=is_equal(def_from,def_to);
                  def_from^.deftype:=procdef;
                end
               else
                { for example delphi allows the assignement from pointers }
                { to procedure variables                                  }
                if (m_pointer_2_procedure in aktmodeswitches) and
                  (def_from^.deftype=pointerdef) and
                  (ppointerdef(def_from)^.definition^.deftype=orddef) and
                  (porddef(ppointerdef(def_from)^.definition)^.typ=uvoid) then
                begin
                   doconv:=tc_equal;
                   b:=true;
                end
               else
               { nil is compatible with procvars }
                if (fromtreetype=niln) then
                 begin
                   doconv:=tc_equal;
                   b:=true;
                 end;
             end;

           objectdef :
             begin
               { object pascal objects }
               if (def_from^.deftype=objectdef) {and
                  pobjectdef(def_from)^.isclass and pobjectdef(def_to)^.isclass }then
                begin
                  doconv:=tc_equal;
                  b:=pobjectdef(def_from)^.isrelated(pobjectdef(def_to));
                end
               else
                { nil is compatible with class instances }
                if (fromtreetype=niln) and (pobjectdef(def_to)^.isclass) then
                 begin
                   doconv:=tc_equal;
                   b:=true;
                 end;
             end;

           classrefdef :
             begin
               { class reference types }
               if (def_from^.deftype=classrefdef) then
                begin
                  doconv:=tc_equal;
                  b:=pobjectdef(pclassrefdef(def_from)^.definition)^.isrelated(
                       pobjectdef(pclassrefdef(def_to)^.definition));
                end
               else
                { nil is compatible with class references }
                if (fromtreetype=niln) then
                 begin
                   doconv:=tc_equal;
                   b:=true;
                 end;
             end;

           filedef :
             begin
               { typed files are all equal to the abstract file type
               name TYPEDFILE in system.pp in is_equal in types.pas
               the problem is that it sholud be also compatible to FILE
               but this would leed to a problem for ASSIGN RESET and REWRITE
               when trying to find the good overloaded function !!
               so all file function are doubled in system.pp
               this is not very beautiful !!}
               if (def_from^.deftype=filedef) and
                  (
                   (
                    (pfiledef(def_from)^.filetype = ft_typed) and
                    (pfiledef(def_to)^.filetype = ft_typed) and
                    (
                     (pfiledef(def_from)^.typed_as = pdef(voiddef)) or
                     (pfiledef(def_to)^.typed_as = pdef(voiddef))
                    )
                   ) or
                   (
                    (
                     (pfiledef(def_from)^.filetype = ft_untyped) and
                     (pfiledef(def_to)^.filetype = ft_typed)
                    ) or
                    (
                     (pfiledef(def_from)^.filetype = ft_typed) and
                     (pfiledef(def_to)^.filetype = ft_untyped)
                    )
                   )
                  ) then
                 begin
                    doconv:=tc_equal;
                    b:=true;
                 end
             end;

           else
             begin
             { assignment overwritten ?? }
               if is_assignment_overloaded(def_from,def_to) then
                b:=true;
             end;
         end;

           { nil is compatible with ansi- and wide strings }
           { no, that isn't true, (FK)
           if (fromtreetype=niln) and (def_to^.deftype=stringdef)
             and (pstringdef(def_to)^.string_typ in [st_ansistring,st_widestring]) then
             begin
                doconv:=tc_equal;
                b:=true;
             end
         else
           }
           { ansi- and wide strings can be assigned to void pointers }
           { no, (FK)
           if (def_from^.deftype=stringdef) and
             (pstringdef(def_from)^.string_typ in [st_ansistring,st_widestring]) and
             (def_to^.deftype=pointerdef) and
             (ppointerdef(def_to)^.definition^.deftype=orddef) and
             (porddef(ppointerdef(def_to)^.definition)^.typ=uvoid) then
             begin
                doconv:=tc_equal;
                b:=true;
             end
         else
           }
           { ansistrings can be assigned to pchar
             this needs an explicit type cast (FK)
           if is_ansistring(def_from) and
             (def_to^.deftype=pointerdef) and
             (ppointerdef(def_to)^.definition^.deftype=orddef) and
             (porddef(ppointerdef(def_to)^.definition)^.typ=uchar) then
             begin
                doconv:=tc_ansistring_2_pchar;
                b:=true;
             end
         else
           }
        isconvertable:=b;
      end;


{****************************************************************************
                          Register Calculation
****************************************************************************}

    { marks an lvalue as "unregable" }
    procedure make_not_regable(p : ptree);
      begin
         case p^.treetype of
            typeconvn :
              make_not_regable(p^.left);
            loadn :
              if p^.symtableentry^.typ=varsym then
                pvarsym(p^.symtableentry)^.var_options :=
                  pvarsym(p^.symtableentry)^.var_options and not vo_regable;
         end;
      end;


    procedure left_right_max(p : ptree);
      begin
        if assigned(p^.left) then
         begin
           if assigned(p^.right) then
            begin
              p^.registers32:=max(p^.left^.registers32,p^.right^.registers32);
              p^.registersfpu:=max(p^.left^.registersfpu,p^.right^.registersfpu);
{$ifdef SUPPORT_MMX}
              p^.registersmmx:=max(p^.left^.registersmmx,p^.right^.registersmmx);
{$endif SUPPORT_MMX}
            end
           else
            begin
              p^.registers32:=p^.left^.registers32;
              p^.registersfpu:=p^.left^.registersfpu;
{$ifdef SUPPORT_MMX}
              p^.registersmmx:=p^.left^.registersmmx;
{$endif SUPPORT_MMX}
            end;
         end;
      end;

    { calculates the needed registers for a binary operator }
    procedure calcregisters(p : ptree;r32,fpu,mmx : word);

      begin
         left_right_max(p);

      { Only when the difference between the left and right registers < the
        wanted registers allocate the amount of registers }

        if assigned(p^.left) then
         begin
           if assigned(p^.right) then
            begin
              if (abs(p^.left^.registers32-p^.right^.registers32)<r32) then
               inc(p^.registers32,r32);
              if (abs(p^.left^.registersfpu-p^.right^.registersfpu)<fpu) then
               inc(p^.registersfpu,fpu);
{$ifdef SUPPORT_MMX}
              if (abs(p^.left^.registersmmx-p^.right^.registersmmx)<mmx) then
               inc(p^.registersmmx,mmx);
{$endif SUPPORT_MMX}
            end
           else
            begin
              if (p^.left^.registers32<r32) then
               inc(p^.registers32,r32);
              if (p^.left^.registersfpu<fpu) then
               inc(p^.registersfpu,fpu);
{$ifdef SUPPORT_MMX}
              if (p^.left^.registersmmx<mmx) then
               inc(p^.registersmmx,mmx);
{$endif SUPPORT_MMX}
            end;
         end;

         { error CGMessage, if more than 8 floating point }
         { registers are needed                         }
         if p^.registersfpu>8 then
          CGMessage(cg_e_too_complex_expr);
      end;

{****************************************************************************
                          Subroutine Handling
****************************************************************************}

{ protected field handling
  protected field can not appear in
  var parameters of function !!
  this can only be done after we have determined the
  overloaded function
  this is the reason why it is not in the parser, PM }

    procedure test_protected_sym(sym : psym);
      begin
         if ((sym^.properties and sp_protected)<>0) and
           ((sym^.owner^.symtabletype=unitsymtable) or
            ((sym^.owner^.symtabletype=objectsymtable) and
           (pobjectdef(sym^.owner^.defowner)^.owner^.symtabletype=unitsymtable))) then
          CGMessage(parser_e_cant_access_protected_member);
      end;


    procedure test_protected(p : ptree);
      begin
        case p^.treetype of
         loadn : test_protected_sym(p^.symtableentry);
     typeconvn : test_protected(p^.left);
        derefn : test_protected(p^.left);
    subscriptn : begin
                 { test_protected(p^.left);
                   Is a field of a protected var
                   also protected ???  PM }
                   test_protected_sym(p^.vs);
                 end;
        end;
      end;


    function is_procsym_load(p:Ptree):boolean;
      begin
         is_procsym_load:=((p^.treetype=loadn) and (p^.symtableentry^.typ=procsym)) or
                          ((p^.treetype=addrn) and (p^.left^.treetype=loadn)
                          and (p^.left^.symtableentry^.typ=procsym)) ;
      end;

   { change a proc call to a procload for assignment to a procvar }
   { this can only happen for proc/function without arguments }
    function is_procsym_call(p:Ptree):boolean;
      begin
        is_procsym_call:=(p^.treetype=calln) and (p^.left=nil) and
             (((p^.symtableprocentry^.typ=procsym) and (p^.right=nil)) or
             ((p^.right<>nil) and (p^.right^.symtableprocentry^.typ=varsym)));
      end;


    function is_assignment_overloaded(from_def,to_def : pdef) : boolean;
       var
          passproc : pprocdef;
          convtyp : tconverttype;
       begin
          is_assignment_overloaded:=false;
          if assigned(overloaded_operators[assignment]) then
            passproc:=overloaded_operators[assignment]^.definition
          else
            exit;
          while passproc<>nil do
            begin
              if is_equal(passproc^.retdef,to_def) and
                 isconvertable(from_def,passproc^.para1^.data,convtyp,
                   ordconstn { nur Dummy},false ) then
                begin
                   is_assignment_overloaded:=true;
                   break;
                end;
              passproc:=passproc^.nextoverloaded;
            end;
       end;

end.
{
  $Log$
  Revision 1.10  1998-11-29 12:40:23  peter
    * newcnv -> not oldcnv

  Revision 1.9  1998/11/26 13:10:42  peter
    * new int - int conversion -dNEWCNV
    * some function renamings

  Revision 1.8  1998/11/17 00:36:42  peter
    * more ansistring fixes

  Revision 1.7  1998/10/14 13:33:24  peter
    * fixed small typo

  Revision 1.6  1998/10/14 12:53:38  peter
    * fixed small tp7 things
    * boolean:=longbool and longbool fixed

  Revision 1.5  1998/10/12 09:49:58  florian
    + support of <procedure var type>:=<pointer> in delphi mode added

  Revision 1.4  1998/09/30 16:42:52  peter
    * fixed bool-bool cnv

  Revision 1.3  1998/09/24 23:49:05  peter
    + aktmodeswitches

  Revision 1.2  1998/09/24 09:02:14  peter
    * rewritten isconvertable to use case
    * array of .. and single variable are compatible

  Revision 1.1  1998/09/23 20:42:22  peter
    * splitted pass_1

}