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|
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %
% Frown --- An LALR(k) parser generator for Haskell 98 %
% Copyright (C) 2001-2005 Ralf Hinze %
% %
% This program is free software; you can redistribute it and/or modify %
% it under the terms of the GNU General Public License (version 2) as %
% published by the Free Software Foundation. %
% %
% 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; see the file COPYING. If not, write to %
% the Free Software Foundation, Inc., 59 Temple Place - Suite 330, %
% Boston, MA 02111-1307, USA. %
% %
% Contact information %
% Email: Ralf Hinze <ralf@cs.uni-bonn.de> %
% Homepage: http://www.informatik.uni-bonn.de/~ralf/ %
% Paper mail: Dr. Ralf Hinze %
% Institut für Informatik III %
% Universität Bonn %
% Römerstraße 164 %
% 53117 Bonn, Germany %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> module Future ( module Future
> )
> where
> import Grammar
> import qualified OrdUniqListSet as Set
> import OrdUniqListSet ( Set )
> import qualified OrdUniqListFM as FM
> import OrdUniqListFM ( FM )
> -- import Base
> import Prettier
%-------------------------------= --------------------------------------------
\section{Lookahead information}
%-------------------------------= --------------------------------------------
> newtype Future = Future { unFuture :: FM Symbol Future }
> deriving (Eq, Ord, Show)
>
> fromList :: [(Symbol, Future)] -> Future
> fromList ts = Future (FM.fromList ts)
>
> instance Pretty Future where
> prettyPrec d (Future s) = prettyPrec d s
>
> union :: Future -> Future -> Future
> union (Future a) (Future b) = Future (FM.union_C union a b)
>
> unionMany :: [Future] -> Future
> unionMany = Future . FM.unionMany_C union . map unFuture
> prune :: Int -> Future -> Future
> prune 0 (Future _ts) = fromList []
> prune n (Future ts) = fromList [ (a, prune (n-1) us) | (a, us) <- FM.toList ts ]
> domain :: Future -> Set Symbol
> domain (Future f) = Set.fromList (map fst (FM.toList f))
>
> lookup :: Future -> Symbol -> Maybe Future
> lookup (Future f) a = FM.lookup f a
>
> empty :: Future -> Bool
> empty (Future f) = FM.null f
|
