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%                                                                             %
%   Frown --- An LALR(k) parser generator for Haskell 98                      %
%   Copyright (C) 2001-2005 Ralf Hinze                                        %
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%   This program is free software; you can redistribute it and/or modify      %
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%   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                                           %
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Grammar file.

> file                          :  many "not special",
>                                  "%{",
>                                  many decl;
>                                  "}%",
>                                  many "not special";

Note that |"not special"| matches every token except the special curly
braces |"%{"| and |"}%"|.

Declaration.

> decl                          :  terminals;
>                               |  nonterminals;
>                               |  fixity;
>                               |  signature;
>                               |  productions;

Terminal declaration.

> terminals                     :  "Terminal", "=", sepBy term "|", ";";
>
> term                          :  opt "*", assoc, terminal;
>                               |  opt "*", assoc, literal, "=", terminal; -- deprecated
>                               |  opt "*", assoc, terminal,          "as", literal;
>                               |  opt "*", assoc, "guard", haskell,  "as", literal;
>
> assoc                         :  ;
>                               |  "left",      Numeral;
>                               |  "right",     Numeral;
>                               |  "nonassoc",  Numeral;

Nonterminal declaration.

> nonterminals                  :  "Nonterminal", "=", sepBy nonterm "|", ";";
>
> nonterm                       :  opt "*", nonterminal;

Fixity declaration.

> fixity                        : "left",      Numeral, terminal, ";";
>                               | "right",     Numeral, terminal, ";";
>                               | "nonassoc",  Numeral, terminal, ";";

Type signature.

> signature                     :  "::", nonterminal, premise, ";";  -- deprecated
>                               |  nonterminal, premise, ";";
>                               |  "::", "*", nonterminal, ";";      -- deprecated
>                               |  "*", nonterminal, ";";
>
> premise                       :  ;
>                               |  "<-", sepBy1 nonterminal ",";

Productions.

> productions                   :  nonterminal, ":", sepBy symbol ",", ";", alts;
>
> alts                          :  ;
>                               |  attributes, "|", sepBy symbol ",", ";", alts;
>
> symbol                        :  "insert",  terminal;
>                               |  "delete",  terminal;
>                               |  "prec",    terminal;
>                               |  terminal;
>                               |  nonterminal;

Nonterminal symbols (|expr0| is a variant of |expr| lacking the
embedded Haskell production).

> nonterminal                   :  expr0, attributes;
>
> expr0                         :  Varid, many aexpr0;
>
> aexpr0                        :  Varid;
>                               |  Conid;
>                               |  literal;
>                               |  "(", sepBy expr ",", ")";
>                               |  "[", sepBy expr ",", "]";
>
> expr                          :  aexpr;
>                               |  Varid, many1 aexpr;
>                               |  Conid, many1 aexpr;
>
> aexpr                         :  Varid;
>                               |  Conid;
>                               |  literal;
>                               |  "(", sepBy expr ",", ")";
>                               |  "[", sepBy expr ",", "]";
>                               |  haskell;                       -- embedded Haskell

Terminal symbols.

> terminal                      :  pat;
>                               |  literal, haskell, attributes;  -- shortcut
>
> pat                           :  apat;
>                               |  Conid, many1 apat;
>
> apat                          :  Conid;
>                               |  literal;                       -- either literal or shortcut
>                               |  "(", sepBy pat ",", ")";
>                               |  "[", sepBy pat ",", "]";
>                               |  haskell;
>
> literal                       :  String;
>                               |  Numeral;
>                               |  Char;

Embedded Haskell (types, patterns, and expressions).

> attributes                    :  ;
>                               |  haskell, attributes;
>
> haskell                       :  "{", many hs, "}";
>
> hs                            :  "not brace";
>                               |  "{", many hs, "}";

Note that |"not brace"| matches every token except the curly braces
|"{"| and |"}"|.