The Language GF
BNF Converter


% File generated by the BNF Converter.


This document was automatically generated by the //BNF-Converter//.

==The lexical structure of GF==

===Literals===

Integer literals //Integer// are nonempty sequences of digits.

Double-precision float literals //Double// have the structure indicated by the regular expression ``digit+ '.' digit+ ('e' ('-')? digit+)?`` i.e. two sequences of digits separated by a decimal point, optionally followed by an unsigned or negative exponent.

Ident literals are recognized by the regular expression
`````(lower | upper) (upper | lower | digit | '_' | ''')*`````

LString literals are recognized by the regular expression
`````(''') (char - ''')* (''')`````

===Reserved words and symbols===

The set of reserved words is the set of terminals 
appearing in the grammar. Those reserved words 
that consist of non-letter characters are called symbols, and 
they are treated in a different way from those that 
are similar to identifiers. The lexer 
follows rules familiar from languages 
like Haskell, C, and Java, including longest match 
and spacing conventions.

The reserved words used in GF are the following:
  | ``Lin`` | ``PType`` | ``Str`` | ``Strs``
  | ``Tok`` | ``Type`` | ``abstract`` | ``case``
  | ``cat`` | ``concrete`` | ``data`` | ``def``
  | ``flags`` | ``fn`` | ``fun`` | ``grammar``
  | ``in`` | ``include`` | ``incomplete`` | ``instance``
  | ``interface`` | ``let`` | ``lin`` | ``lincat``
  | ``lindef`` | ``lintype`` | ``of`` | ``open``
  | ``oper`` | ``out`` | ``package`` | ``param``
  | ``pattern`` | ``pre`` | ``printname`` | ``resource``
  | ``reuse`` | ``strs`` | ``table`` | ``tokenizer``
  | ``transfer`` | ``union`` | ``var`` | ``variants``
  | ``where`` | ``with``  |  |

The symbols used in GF  the following:
  | ! | $ | % | (
  | ) | * | ** | +
  | ++ | , | - | ->
  | . | / | : | ;
  | < | = | => | >
  | ? | @ | [ | \
  | ] | _ | { | |
  | }  |  |  |

===Comments===

Single-line comments begin with --.
Multiple-line comments are  enclosed with {- and -}.

==The syntactic structure of GF ==
Non-terminals are enclosed between < and >.
The symbols **->** (production), **|** (union)
and **eps** (empty rule) belong to the BNF notation.
All other symbols are terminals.

  | //Altern// | -> | //Exp// ``/`` //Exp//
  | //Bind// | -> | //Ident//
  |  |  **|**  | ``_``
  | //Case// | -> | //[PattAlt]// ``=>`` //Exp//
  | //CatDef// | -> | ``[`` //Ident// //[DDecl]// ``]``
  |  |  **|**  | ``[`` //Ident// //[DDecl]// ``]`` ``{`` //Integer// ``}``
  |  |  **|**  | //Ident// //[DDecl]//
  | //ComplMod// | -> | **eps**
  |  |  **|**  | ``incomplete``
  | //ConcExp// | -> | //Ident// //[Transfer]//
  | //ConcSpec// | -> | //Ident// ``=`` //ConcExp//
  | //DDecl// | -> | ``(`` //[Bind]// ``:`` //Exp// ``)``
  |  |  **|**  | //Exp4//
  | //DataConstr// | -> | //Ident//
  |  |  **|**  | //Ident// ``.`` //Ident//
  | //DataDef// | -> | //Ident// ``=`` //[DataConstr]//
  | //Decl// | -> | ``(`` //[Bind]// ``:`` //Exp// ``)``
  |  |  **|**  | //Exp2//
  | //Def// | -> | //[Name]// ``:`` //Exp//
  |  |  **|**  | //[Name]// ``=`` //Exp//
  |  |  **|**  | //[Name]// ``:`` //Exp// ``=`` //Exp//
  |  |  **|**  | //Name// //[Patt]// ``=`` //Exp//
  | //Equation// | -> | //[Patt]// ``->`` //Exp//
  | //Exp// | -> | ``\`` //[Bind]// ``->`` //Exp//
  |  |  **|**  | ``\`` ``\`` //[Bind]// ``=>`` //Exp//
  |  |  **|**  | //Exp1// ``++`` //Exp//
  |  |  **|**  | ``fn`` ``{`` //[Equation]// ``}``
  |  |  **|**  | //Exp1// ``+`` //Exp//
  |  |  **|**  | ``let`` ``{`` //[LocDef]// ``}`` ``in`` //Exp//
  |  |  **|**  | ``let`` //[LocDef]// ``in`` //Exp//
  |  |  **|**  | //Decl// ``->`` //Exp//
  |  |  **|**  | //Exp1// ``=>`` //Exp//
  |  |  **|**  | //Exp1// ``where`` ``{`` //[LocDef]// ``}``
  |  |  **|**  | //Exp1//
  | //Exps// | -> | //Exp4// //Exps//
  |  |  **|**  | **eps**
  | //Extend// | -> | //[Included]// ``**``
  |  |  **|**  | **eps**
  | //FileName// | -> | //Ident// //FileName//
  |  |  **|**  | ``.`` //FileName//
  |  |  **|**  | //Ident//
  |  |  **|**  | ``-`` //FileName//
  |  |  **|**  | ``/`` //FileName//
  |  |  **|**  | //String//
  | //FlagDef// | -> | //Ident// ``=`` //Ident//
  | //FunDef// | -> | //[Ident]// ``:`` //Exp//
  | //Grammar// | -> | //[ModDef]//
  | //IncludeDecl// | -> | ``include`` //[FileName]//
  |  |  **|**  | **eps**
  | //Included// | -> | //Ident//
  |  |  **|**  | //Ident// ``-`` ``[`` //[Ident]// ``]``
  |  |  **|**  | //Ident// ``[`` //[Ident]// ``]``
  | //Label// | -> | //Ident//
  |  |  **|**  | ``$`` //Integer//
  | //LocDef// | -> | //[Ident]// ``:`` //Exp//
  |  |  **|**  | //[Ident]// ``=`` //Exp//
  |  |  **|**  | //[Ident]// ``:`` //Exp// ``=`` //Exp//
  | //ModBody// | -> | //Extend// //Opens// ``{`` //[TopDef]// ``}``
  |  |  **|**  | ``reuse`` //Ident//
  |  |  **|**  | ``union`` //[Included]//
  |  |  **|**  | //Ident// ``with`` //[OpenDecl]//
  |  |  **|**  | //[Included]// ``**`` //Ident// ``with`` //[OpenDecl]//
  | //ModDef// | -> | ``grammar`` //Ident// ``=`` ``{`` ``abstract`` ``=`` //Ident// ``;`` //[ConcSpec]// ``}``
  |  |  **|**  | //ComplMod// //ModType// ``=`` //ModBody//
  |  |  **|**  | //ModDef// ``;``
  | //ModType// | -> | ``abstract`` //Ident//
  |  |  **|**  | ``concrete`` //Ident// ``of`` //Ident//
  |  |  **|**  | ``instance`` //Ident// ``of`` //Ident//
  |  |  **|**  | ``interface`` //Ident//
  |  |  **|**  | ``resource`` //Ident//
  |  |  **|**  | ``transfer`` //Ident// ``:`` //OpenDecl// ``->`` //OpenDecl//
  | //Name// | -> | //Ident//
  |  |  **|**  | ``[`` //Ident// ``]``
  | //OldGrammar// | -> | //IncludeDecl// //[TopDef]//
  | //OpenDecl// | -> | //Ident//
  |  |  **|**  | ``(`` //QualOpen// //Ident// ``=`` //Ident// ``)``
  |  |  **|**  | ``(`` //QualOpen// //Ident// ``)``
  | //Opens// | -> | **eps**
  |  |  **|**  | ``open`` //[OpenDecl]// ``in``
  | //ParConstr// | -> | //Ident// //[DDecl]//
  | //ParDef// | -> | //Ident//
  |  |  **|**  | //Ident// ``=`` //[ParConstr]//
  |  |  **|**  | //Ident// ``=`` ``(`` ``in`` //Ident// ``)``
  | //Patt// | -> | //Ident// //[Patt]//
  |  |  **|**  | //Ident// ``.`` //Ident// //[Patt]//
  |  |  **|**  | //Patt1//
  | //PattAlt// | -> | //Patt//
  | //PattAss// | -> | //[Ident]// ``=`` //Patt//
  | //PattTupleComp// | -> | //Patt//
  | //PrintDef// | -> | //[Name]// ``=`` //Exp//
  | //QualOpen// | -> | **eps**
  |  |  **|**  | ``incomplete``
  |  |  **|**  | ``interface``
  | //Sort// | -> | ``PType``
  |  |  **|**  | ``Str``
  |  |  **|**  | ``Strs``
  |  |  **|**  | ``Tok``
  |  |  **|**  | ``Type``
  | //TopDef// | -> | ``cat`` //[CatDef]//
  |  |  **|**  | ``data`` //[DataDef]//
  |  |  **|**  | ``def`` //[Def]//
  |  |  **|**  | ``flags`` //[FlagDef]//
  |  |  **|**  | ``fun`` //[FunDef]//
  |  |  **|**  | ``data`` //[FunDef]//
  |  |  **|**  | ``lin`` //[Def]//
  |  |  **|**  | ``lincat`` //[PrintDef]//
  |  |  **|**  | ``lindef`` //[Def]//
  |  |  **|**  | ``lintype`` //[Def]//
  |  |  **|**  | ``oper`` //[Def]//
  |  |  **|**  | ``package`` //Ident// ``=`` ``{`` //[TopDef]// ``}`` ``;``
  |  |  **|**  | ``param`` //[ParDef]//
  |  |  **|**  | ``pattern`` //[Def]//
  |  |  **|**  | ``printname`` ``cat`` //[PrintDef]//
  |  |  **|**  | ``printname`` ``fun`` //[PrintDef]//
  |  |  **|**  | ``printname`` //[PrintDef]//
  |  |  **|**  | ``tokenizer`` //Ident// ``;``
  |  |  **|**  | ``transfer`` //[Def]//
  |  |  **|**  | ``var`` //[Def]//
  | //Transfer// | -> | ``(`` ``transfer`` ``in`` //OpenDecl// ``)``
  |  |  **|**  | ``(`` ``transfer`` ``out`` //OpenDecl// ``)``
  | //TupleComp// | -> | //Exp//
  | //[Ident]// | -> | //Ident//
  |  |  **|**  | //Ident// ``,`` //[Ident]//
  | //[Altern]// | -> | **eps**
  |  |  **|**  | //Altern//
  |  |  **|**  | //Altern// ``;`` //[Altern]//
  | //[Bind]// | -> | **eps**
  |  |  **|**  | //Bind//
  |  |  **|**  | //Bind// ``,`` //[Bind]//
  | //[Case]// | -> | //Case//
  |  |  **|**  | //Case// ``;`` //[Case]//
  | //[CatDef]// | -> | //CatDef// ``;``
  |  |  **|**  | //CatDef// ``;`` //[CatDef]//
  | //[ConcSpec]// | -> | **eps**
  |  |  **|**  | //ConcSpec//
  |  |  **|**  | //ConcSpec// ``;`` //[ConcSpec]//
  | //[DDecl]// | -> | **eps**
  |  |  **|**  | //DDecl// //[DDecl]//
  | //[DataConstr]// | -> | **eps**
  |  |  **|**  | //DataConstr//
  |  |  **|**  | //DataConstr// ``|`` //[DataConstr]//
  | //[DataDef]// | -> | //DataDef// ``;``
  |  |  **|**  | //DataDef// ``;`` //[DataDef]//
  | //[Def]// | -> | //Def// ``;``
  |  |  **|**  | //Def// ``;`` //[Def]//
  | //[Equation]// | -> | **eps**
  |  |  **|**  | //Equation//
  |  |  **|**  | //Equation// ``;`` //[Equation]//
  | //[Exp]// | -> | **eps**
  |  |  **|**  | //Exp//
  |  |  **|**  | //Exp// ``;`` //[Exp]//
  | //[FileName]// | -> | //FileName// ``;``
  |  |  **|**  | //FileName// ``;`` //[FileName]//
  | //[FlagDef]// | -> | //FlagDef// ``;``
  |  |  **|**  | //FlagDef// ``;`` //[FlagDef]//
  | //[FunDef]// | -> | //FunDef// ``;``
  |  |  **|**  | //FunDef// ``;`` //[FunDef]//
  | //[Included]// | -> | **eps**
  |  |  **|**  | //Included//
  |  |  **|**  | //Included// ``,`` //[Included]//
  | //[LocDef]// | -> | **eps**
  |  |  **|**  | //LocDef//
  |  |  **|**  | //LocDef// ``;`` //[LocDef]//
  | //[ModDef]// | -> | **eps**
  |  |  **|**  | //ModDef// //[ModDef]//
  | //[Name]// | -> | //Name//
  |  |  **|**  | //Name// ``,`` //[Name]//
  | //[OpenDecl]// | -> | **eps**
  |  |  **|**  | //OpenDecl//
  |  |  **|**  | //OpenDecl// ``,`` //[OpenDecl]//
  | //[ParConstr]// | -> | **eps**
  |  |  **|**  | //ParConstr//
  |  |  **|**  | //ParConstr// ``|`` //[ParConstr]//
  | //[ParDef]// | -> | //ParDef// ``;``
  |  |  **|**  | //ParDef// ``;`` //[ParDef]//
  | //[Patt]// | -> | //Patt1//
  |  |  **|**  | //Patt1// //[Patt]//
  | //[PattAlt]// | -> | //PattAlt//
  |  |  **|**  | //PattAlt// ``|`` //[PattAlt]//
  | //[PattAss]// | -> | **eps**
  |  |  **|**  | //PattAss//
  |  |  **|**  | //PattAss// ``;`` //[PattAss]//
  | //[PattTupleComp]// | -> | **eps**
  |  |  **|**  | //PattTupleComp//
  |  |  **|**  | //PattTupleComp// ``,`` //[PattTupleComp]//
  | //[PrintDef]// | -> | //PrintDef// ``;``
  |  |  **|**  | //PrintDef// ``;`` //[PrintDef]//
  | //[TopDef]// | -> | **eps**
  |  |  **|**  | //TopDef// //[TopDef]//
  | //[Transfer]// | -> | **eps**
  |  |  **|**  | //Transfer// //[Transfer]//
  | //[TupleComp]// | -> | **eps**
  |  |  **|**  | //TupleComp//
  |  |  **|**  | //TupleComp// ``,`` //[TupleComp]//
  | //Exp1// | -> | //Exp1// ``**`` //Exp2//
  |  |  **|**  | //Exp1// ``!`` //Exp2//
  |  |  **|**  | //Exp1// ``*`` //Exp2//
  |  |  **|**  | //Exp2//
  | //Exp2// | -> | //Exp2// //Exp3//
  |  |  **|**  | ``case`` //Exp// ``of`` ``{`` //[Case]// ``}``
  |  |  **|**  | //Ident// ``@`` //Exp4//
  |  |  **|**  | ``Lin`` //Ident//
  |  |  **|**  | ``pre`` ``{`` //Exp// ``;`` //[Altern]// ``}``
  |  |  **|**  | ``strs`` ``{`` //[Exp]// ``}``
  |  |  **|**  | ``table`` //Exp4// ``{`` //[Case]// ``}``
  |  |  **|**  | ``table`` ``{`` //[Case]// ``}``
  |  |  **|**  | ``table`` //Exp4// ``[`` //[Exp]// ``]``
  |  |  **|**  | ``variants`` ``{`` //[Exp]// ``}``
  |  |  **|**  | //Exp3//
  | //Exp3// | -> | //Exp3// ``.`` //Label//
  |  |  **|**  | ``%`` //Ident// ``.`` //Ident//
  |  |  **|**  | ``{`` //Ident// ``.`` //Ident// ``}``
  |  |  **|**  | //Exp4//
  | //Exp4// | -> | ``%`` //Ident// ``%``
  |  |  **|**  | ``{`` //Ident// ``}``
  |  |  **|**  | ``data``
  |  |  **|**  | ``[`` ``]``
  |  |  **|**  | //Ident//
  |  |  **|**  | ``(`` ``in`` //Ident// ``)``
  |  |  **|**  | //Integer//
  |  |  **|**  | //LString//
  |  |  **|**  | ``[`` //Ident// //Exps// ``]``
  |  |  **|**  | ``?``
  |  |  **|**  | ``{`` //[LocDef]// ``}``
  |  |  **|**  | //Sort//
  |  |  **|**  | //String//
  |  |  **|**  | ``[`` //String// ``]``
  |  |  **|**  | ``<`` //[TupleComp]// ``>``
  |  |  **|**  | ``<`` //Exp// ``:`` //Exp// ``>``
  |  |  **|**  | ``(`` //Exp// ``)``
  | //Patt1// | -> | ``{`` //Ident// ``}``
  |  |  **|**  | //Integer//
  |  |  **|**  | //Ident// ``.`` //Ident//
  |  |  **|**  | ``{`` //[PattAss]// ``}``
  |  |  **|**  | //String//
  |  |  **|**  | ``<`` //[PattTupleComp]// ``>``
  |  |  **|**  | //Ident//
  |  |  **|**  | ``_``
  |  |  **|**  | ``(`` //Patt// ``)``