# This is a file defining the BPEG grammar using BPEG syntax

grammar;
grammar = __ @[main-pattern]extended-pat __ (*def % (__`;__)) ?(__ `;) __;
def = @[name]ref __ `= __ @[definition]extended-pat;

# This is used for command line arguments:
string-grammar = *(`\ pat ?`; / .);

pat = empty / dot / string / char-range / char / escape-range / escape / no / anything-but
    / upto-and / repeat / after / before / capture / replace / ref / parens;

empty = `/ >(__ (`}/`}));
dot = `.;
string = (
        `" @[s]*(escape / ~`") `"
      / `' @[s]*(escape / ~`') `'
    );
char-range = `` @[low]. `- @[high].;
char = `` @[s].;
escape-range = `\ @[low]escape-sequence `- @[high]escape-sequence;
escape = `\ @[s]escape-sequence;
escape-sequence = (
        1-3 `0-7
      / `x 2 (`0-9/`a-f/`A-F)
      /`a/`b/`e/`n/`r/`t/`v / . / \n
    );
no = `! _ @pat;
anything-but = `~ ?`~ _ @pat;
upto-and = `& ?`& _ @pat;
repeat = (
           @[min]int _ `- _ @[max]int
      /    @[min]{->"0"}    @[max]int _ `-
      /    @[min]int _ `+   @[max](/)
      /    @[min]           @[max]int
      / `+ @[min]{->"1"}    @[max](/)
      / `* @[min]{->"0"}    @[max](/)
      / `? @[min]{->"0"}    @[max]{->"1"}
    ) _ @[repeat-pat]pat ?( __ `% __ @[sep]pat);
after = `< _ pat;
before = `> _ pat;
capture = `@ ?(_ `[ @[capture-name]ref `]) _ @[capture]pat;
replace = `{ __ (
      ?(@[replace-pat]extended-pat __) "=>" ?(__ @[replacement]string)
    ) __ `};
ref = @[name](
        "^^" / "^" / "__" / "_" / "$$" / "$" /
        (`a-z/`A-Z) *(`a-z/`A-Z/`0-9/`-));

parens = `( __ extended-pat __ `);

chain = +@pat % (__);
otherwise = +@(chain/pat) % (__`/__);
extended-pat = otherwise / chain / pat;

_ = *(`  / \t);
__ = *(`  / \t / \r / \n / comment);
hash-comment = `# *.;

# Note: comments are undefined by default in regular BPEG
comment = hash-comment;