1# RON grammar 2 3This file describes the structure of a RON file in [EBNF notation][ebnf]. 4If extensions are enabled, some rules will be replaced. For that, see the 5[extensions document][exts] which describes all extensions and what they override. 6 7[ebnf]: https://en.wikipedia.org/wiki/Extended_Backus–Naur_form 8[exts]: ./extensions.md 9 10## RON file 11 12```ebnf 13RON = [extensions], ws, value, ws; 14``` 15 16## Whitespace and comments 17 18```ebnf 19ws = { ws_single, comment }; 20ws_single = "\n" | "\t" | "\r" | " "; 21comment = ["//", { no_newline }, "\n"] | ["/*", { ? any character ? }, "*/"]; 22``` 23 24## Commas 25 26```ebnf 27comma = ws, ",", ws; 28``` 29 30## Extensions 31 32```ebnf 33extensions = { "#", ws, "!", ws, "[", ws, extensions_inner, ws, "]", ws }; 34extensions_inner = "enable", ws, "(", extension_name, { comma, extension_name }, [comma], ws, ")"; 35``` 36 37For the extension names see the [`extensions.md`][exts] document. 38 39## Value 40 41```ebnf 42value = unsigned | signed | float | string | char | bool | option | list | map | tuple | struct | enum_variant; 43``` 44 45## Numbers 46 47```ebnf 48digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9"; 49hex_digit = "A" | "a" | "B" | "b" | "C" | "c" | "D" | "d" | "E" | "e" | "F" | "f"; 50unsigned = (["0", ("b" | "o")], digit, { digit | '_' } | 51 "0x", (digit | hex_digit), { digit | hex_digit | '_' }); 52signed = ["+" | "-"], unsigned; 53float = float_std | float_frac; 54float_std = ["+" | "-"], digit, { digit }, ".", {digit}, [float_exp]; 55float_frac = ".", digit, {digit}, [float_exp]; 56float_exp = ("e" | "E"), digit, {digit}; 57``` 58 59## String 60 61```ebnf 62string = string_std | string_raw; 63string_std = "\"", { no_double_quotation_marks | string_escape }, "\""; 64string_escape = "\\", ("\"" | "\\" | "b" | "f" | "n" | "r" | "t" | ("u", unicode_hex)); 65string_raw = "r" string_raw_content; 66string_raw_content = ("#", string_raw_content, "#") | "\"", { unicode_non_greedy }, "\""; 67``` 68 69> Note: Raw strings start with an `r`, followed by n `#`s and a quotation mark 70 `"`. They may contain any characters or escapes (except the end sequence). 71 A raw string ends with a quotation mark (`"`), followed by n `#`s. n may be 72 any number, including zero. 73 Example: 74 ```rust 75r##"This is a "raw string". It can contain quotations or 76backslashes (\)!"## 77 ``` 78Raw strings cannot be written in EBNF, as they are context-sensitive. 79Also see [the Rust document] about context-sensitivity of raw strings. 80 81[the Rust document]: https://github.com/rust-lang/rust/blob/d046ffddc4bd50e04ffc3ff9f766e2ac71f74d50/src/grammar/raw-string-literal-ambiguity.md 82 83## Char 84 85```ebnf 86char = "'", (no_apostrophe | "\\\\" | "\\'"), "'"; 87``` 88 89## Boolean 90 91```ebnf 92bool = "true" | "false"; 93``` 94 95## Optional 96 97```ebnf 98option = "Some", ws, "(", ws, value, ws, ")"; 99``` 100 101## List 102 103```ebnf 104list = "[", [value, { comma, value }, [comma]], "]"; 105``` 106 107## Map 108 109```ebnf 110map = "{", [map_entry, { comma, map_entry }, [comma]], "}"; 111map_entry = value, ws, ":", ws, value; 112``` 113 114## Tuple 115 116```ebnf 117tuple = "(", [value, { comma, value }, [comma]], ")"; 118``` 119 120## Struct 121 122```ebnf 123struct = unit_struct | tuple_struct | named_struct; 124unit_struct = ident | "()"; 125tuple_struct = [ident], ws, tuple; 126named_struct = [ident], ws, "(", [named_field, { comma, named_field }, [comma]], ")"; 127named_field = ident, ws, ":", value; 128``` 129 130## Enum 131 132```ebnf 133enum_variant = enum_variant_unit | enum_variant_tuple | enum_variant_named; 134enum_variant_unit = ident; 135enum_variant_tuple = ident, ws, tuple; 136enum_variant_named = ident, ws, "(", [named_field, { comma, named_field }, [comma]], ")"; 137``` 138