EBNF

# ISO/IEC 14977
space = "\s" | "\t";
newline = "\n" | "\r";
white space = { space };

upper 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";
lower 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";
letter = upper letter | lower letter;

zero = "0";
nonzero = "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;
digit = zero | nonzero;
positive = nonzero, { digit };
decimal = ( positive, ".", { digit }, positive )
        | ( positive, ".", zero )
        | ( zero, ".", { digit }, positive );
negative = "-", decimal | positive;
number = negative | positive | decimal | zero;

symbol = "." | "?" | "!"| '"' | "'" | "," | "_" | "@" | "$" | "%" | "^" | "&" | "/" | "\" | "`" | "~" | "-" | "|" | "=" | "*" | "<" | ">" | "+";

character = letter | digit | symbol;
word = letter | symbol, { character };

single quoted = "'", [{ '\', ANY | "'"?, ANY }], "'";
double quoted = '"', [{ '\', ANY | '"'?, ANY }], '"';
text = single quote | double quote

comment = "#", { any };
symbol = "?" | "!" | "_" | "@" | "$" | "%" | "^" | "&" | "/" | "\" | "~" | "-" | "|" | "=" | "*" | "<" | ">" | ";" | "+";

brace container = "{", white space, [ assignment, { white space, ",", white space, assignment } ], white space, "}";
bracket container = "[", white space, [ arguments ], white space, "]";

function = word, ["(", [arguments], ")"];
argument = ",", { space }, expression;
arguments = "(", { expression, { argument } }, ")";
expression = number | text | container | function;
expressions = [{ expression, [space] }];
assignment = word, ":", white space, expressions;

indent = { 2 * white space }
line = expression | assignment, newline;
lines = { line };