%header%

GRAMMARTYPE = "LL"

DESCRIPTION = "A grammar for FEN setup notation."

AUTHOR      = "Wieger Wesselink, <wieger at 10x10 dot org>"
VERSION     = "1.2"
DATE        = "1 January 2016"

LICENSE     = "Distributed under the Boost Software License, Version 1.0.
               See http://www.boost.org/LICENSE_1_0.txt."

COPYRIGHT   = "Copyright (c) 2009-2016 Wieger Wesselink. All rights reserved."

%tokens%

COLOR                      = <<[WB?]>>
KING                       = "K"
ALPHASQUARE                = <<[a-h][1-8]>>
NUMSQUARE                  = <<([1-9][\d]*)|(0[1-9][\d]*)|0>>
HYPHEN                     = "-"
COMMA                      = ","
COLON                      = ":"
DOT                        = "."
WHITESPACE                 = <<[ \t\n\r]+>> %ignore%

%productions%

Fen                        = COLOR (NumericSquares | AlphaNumericSquares) DOT?       ;
NumericSquares             = (COLON COLOR NumericSquareSequence)+                    ;
NumericSquareSequence      = NumericSquareRange (COMMA NumericSquareRange)*          ;
NumericSquareRange         = KING? NUMSQUARE (HYPHEN NUMSQUARE)?                     ;
AlphaNumericSquares        = (COLON COLOR AlphaNumericSquareSequence)+               ;
AlphaNumericSquareSequence = KING? ALPHASQUARE (COMMA KING? ALPHASQUARE)*            ;