ebnf: add some doc

Signed-off-by: Alejandro Mery <amery@geeks.cl>

ebnf/doc.go

@@ -0,0 +1,37 @@
+/*
+Package ebmf implements an ISO/IEC 14977
+Extended Backus–Naur Form parser, verifiers,
+and additional related helpers for AsciiGoat
+
+A syntax highlighter for vim and a copy of the final draft of the standard
+are included in the doc/ directory. The official standard can be downloaded from
+http://standards.iso.org/ittf/PubliclyAvailableStandards/s026153_ISO_IEC_14977_1996(E).zip
+
+An uberly simplified version of the EBNF grammar looks like:
+
+  letter = "A" | "B" | "C" | "D" | "E" | "F" | "G"
+         | "H" | "I" | "J" | "K" | "L" | "M" | "N"
+         | "O" | "P" | "Q" | "R" | "S" | "T" | "U"
+         | "V" | "W" | "X" | "Y" | "Z" ;
+  digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
+  symbol = "[" | "]" | "{" | "}" | "(" | ")" | "<" | ">"
+         | "'" | '"' | "=" | "|" | "." | "," | ";" ;
+  character = letter | digit | symbol | "_" ;
+
+  identifier = letter , { letter | digit | "_" } ;
+  terminal = "'" , character , { character } , "'"
+           | '"' , character , { character } , '"' ;
+
+  lhs = identifier ;
+  rhs = identifier
+      | terminal
+      | "[" , rhs , "]"
+      | "{" , rhs , "}"
+      | "(" , rhs , ")"
+      | rhs , "|" , rhs
+      | rhs , "," , rhs ;
+
+  rule = lhs , "=" , rhs , ";" ;
+  grammar = { rule } ;
+*/
+package ebnf