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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 %
% %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%if False
> %{
start;
start : many start;
%endif
Note that the predefined rules are left-recursive and `run' using
constant stack space. Also note that we define rules for arity zero
and arity one (the arity specifies the number of attributes/semantic
values). The primed versions of the rules work on Hughes's efficient
sequence type (a sequence of |a|'s is represented by a function of
type |[a] -> [a]|).
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\subsection{Optional elements}
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
Arity zero.
> opt x <- x;
> opt x : ;
> | x;
Arity one.
> opt x {Maybe a} <- x {a};
> opt x {Nothing} : ;
> {Just a} | x {a};
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\subsection{Repetition of elements}
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
Arity zero.
> many x <- x;
> many x : ;
> | many x, x;
>
> many1 x <- x;
> many1 x : x, many x;
Arity one.
> many x {[a]} <- x {a};
> many x {s []} : many' x {s};
>
> many' x {[a] -> [a]} <- x {a};
> many' x {\ as -> as} : ;
> {\ as -> s (a : as)} | many' x {s}, x {a};
>
> many1 x {[a]} <- x {a};
> many1 x {a : as} : x {a}, many x {as};
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\subsection{Repetition of elements separated by a second element}
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
Arity zero.
> sepBy x sep <- x, sep;
> sepBy x sep : ;
> | sepBy1 x sep;
>
> sepBy1 x sep <- x, sep;
> sepBy1 x sep : x;
> | sepBy1 x sep, sep, x;
Arity one.
> sepBy x sep {[a]} <- x {a}, sep;
> sepBy x sep {[]} : ;
> {as} | sepBy1 x sep {as};
>
> sepBy1 x sep {[a]} <- x {a}, sep;
> sepBy1 x sep {s []} : sepBy1' x sep {s};
>
> sepBy1' x sep {[a] -> [a]} <- x {a}, sep;
> sepBy1' x sep
> {\ as -> a : as} : x {a};
> {\ as -> s (a : as)} | sepBy1' x sep {s}, sep, x {a};
TODO: also versions where |sep| has arity one.
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\subsection{Repetition of possibly empty elements separated by a second element}
% - - - - - - - - - - - - - - - = - - - - - - - - - - - - - - - - - - - - - - -
\Todo{better name.}
Arity zero.
> optSepBy x sep <- x, sep;
> optSepBy x sep : ;
> | x;
> | optSepBy x sep, sep;
> | optSepBy x sep, sep, x;
Arity one.
> optSepBy x sep {[a]} <- x {a}, sep;
> optSepBy x sep {s []} : optSepBy' x sep {s};
>
> optSepBy' x sep {[a] -> [a]} <- x {a}, sep;
> optSepBy' x sep
> {\ as -> as} : ;
> {\ as -> a : as} | x {a};
> {\ as -> s as} | optSepBy' x sep {s}, sep;
> {\ as -> s (a : as)} | optSepBy' x sep {s}, sep, x {a};
%if False
> }%
%endif
|
