mirror of
https://github.com/AleoHQ/leo.git
synced 2024-12-21 16:41:42 +03:00
180 lines
6.3 KiB
Plaintext
180 lines
6.3 KiB
Plaintext
; Copyright (C) 2019-2021 Aleo Systems Inc.
|
|
; This file is part of the Leo library.
|
|
|
|
; The Leo library is free software: you can redistribute it and/or modify
|
|
; it under the terms of the GNU General Public License as published by
|
|
; the Free Software Foundation, either version 3 of the License, or
|
|
; (at your option) any later version.
|
|
|
|
; The Leo library is distributed in the hope that it will be useful,
|
|
; but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
; GNU General Public License for more details.
|
|
|
|
; You should have received a copy of the GNU General Public License
|
|
; along with the Leo library. If not, see <https://www.gnu.org/licenses/>.
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
; Introduction
|
|
; ------------
|
|
|
|
; This file contains an ABNF (Augmented Backus-Naur Form) grammar of Leo string formatting.
|
|
; Background on ABNF is provided later in this file.
|
|
|
|
; This grammar provides an official definition of how format strings
|
|
; are parsed for printed by the Leo compiler.
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
; Background on ABNF
|
|
; ------------------
|
|
|
|
; ABNF is an Internet standard:
|
|
; see RFC 5234 at https://www.rfc-editor.org/info/rfc5234
|
|
; and RFC 7405 at https://www.rfc-editor.org/info/rfc7405.
|
|
; It is used to specify the syntax of JSON, HTTP, and other standards.
|
|
|
|
; ABNF adds conveniences and makes slight modifications
|
|
; to Backus-Naur Form (BNF),
|
|
; without going beyond context-free grammars.
|
|
|
|
; Instead of BNF's angle-bracket notation for nonterminals,
|
|
; ABNF uses case-insensitive names consisting of letters, digits, and dashes,
|
|
; e.g. `HTTP-message` and `IPv6address`.
|
|
; ABNF includes an angle-bracket notation for prose descriptions,
|
|
; e.g. `<host, see [RFC3986], Section 3.2.2>`,
|
|
; usable as last resort in the definiens of a nonterminal.
|
|
|
|
; While BNF allows arbitrary terminals,
|
|
; ABNF uses only natural numbers as terminals,
|
|
; and denotes them via:
|
|
; (i) binary, decimal, or hexadecimal sequences,
|
|
; e.g. `%b1.11.1010`, `%d1.3.10`, and `%x.1.3.A`
|
|
; all denote the sequence of terminals [1, 3, 10];
|
|
; (ii) binary, decimal, or hexadecimal ranges,
|
|
; e.g. `%x30-39` denotes any singleton sequence of terminals
|
|
; [_n_] with 48 <= _n_ <= 57 (an ASCII digit);
|
|
; (iii) case-sensitive ASCII strings,
|
|
; e.g. `%s"Ab"` denotes the sequence of terminals [65, 98];
|
|
; and (iv) case-insensitive ASCII strings,
|
|
; e.g. `%i"ab"`, or just `"ab"`, denotes
|
|
; any sequence of terminals among
|
|
; [65, 66],
|
|
; [65, 98],
|
|
; [97, 66], and
|
|
; [97, 98].
|
|
; ABNF terminals in suitable sets represent ASCII or Unicode characters.
|
|
|
|
; ABNF allows repetition prefixes `n*m`,
|
|
; where `n` and `m` are natural numbers in decimal notation;
|
|
; if absent,
|
|
; `n` defaults to 0, and
|
|
; `m` defaults to infinity.
|
|
; For example,
|
|
; `1*4HEXDIG` denotes one to four `HEXDIG`s,
|
|
; `*3DIGIT` denotes up to three `DIGIT`s, and
|
|
; `1*OCTET` denotes one or more `OCTET`s.
|
|
; A single `n` prefix
|
|
; abbreviates `n*n`,
|
|
; e.g. `3DIGIT` denotes three `DIGIT`s.
|
|
|
|
; Instead of BNF's `|`, ABNF uses `/` to separate alternatives.
|
|
; Repetition prefixes have precedence over juxtapositions,
|
|
; which have precedence over `/`.
|
|
; Round brackets group things and override the aforementioned precedence rules,
|
|
; e.g. `*(WSP / CRLF WSP)` denotes sequences of terminals
|
|
; obtained by repeating, zero or more times,
|
|
; either (i) a `WSP` or (ii) a `CRLF` followed by a `WSP`.
|
|
; Square brackets also group things but make them optional,
|
|
; e.g. `[":" port]` is equivalent to `0*1(":" port)`.
|
|
|
|
; Instead of BNF's `::=`, ABNF uses `=` to define nonterminals,
|
|
; and `=/` to incrementally add alternatives
|
|
; to previously defined nonterminals.
|
|
; For example, the rule `BIT = "0" / "1"`
|
|
; is equivalent to `BIT = "0"` followed by `BIT =/ "1"`.
|
|
|
|
; The syntax of ABNF itself is formally specified in ABNF
|
|
; (in Section 4 of the aforementioned RFC 5234,
|
|
; after the syntax and semantics of ABNF
|
|
; are informally specified in natural language
|
|
; (in Sections 1, 2, and 3 of the aforementioned RFC 5234).
|
|
; The syntax rules of ABNF prescribe the ASCII codes allowed for
|
|
; white space (spaces and horizontal tabs),
|
|
; line endings (carriage returns followed by line feeds),
|
|
; and comments (semicolons to line endings).
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
; Structure
|
|
; ---------
|
|
|
|
; This ABNF grammar consists of one grammar:
|
|
; that describes how a Leo string-literal is parsed
|
|
; for formatting.
|
|
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
; Format String
|
|
; -------------------
|
|
|
|
not-double-quote-or-backslash-or-brace = %x0-21
|
|
/ %x23-5B
|
|
/ %x5D-7A
|
|
/ %x7C
|
|
/ %x7E-10FFFF
|
|
; anything but " or \ or { or }
|
|
|
|
double-quote = %x22 ; "
|
|
|
|
single-quote = %x27 ; '
|
|
|
|
single-quote-escape = "\" single-quote ; \'
|
|
|
|
double-quote-escape = "\" double-quote ; \"
|
|
|
|
backslash-escape = "\\"
|
|
|
|
line-feed-escape = %s"\n"
|
|
|
|
carriage-return-escape = %s"\r"
|
|
|
|
horizontal-tab-escape = %s"\t"
|
|
|
|
null-character-escape = "\0"
|
|
|
|
simple-character-escape = single-quote-escape
|
|
/ double-quote-escape
|
|
/ backslash-escape
|
|
/ line-feed-escape
|
|
/ carriage-return-escape
|
|
/ horizontal-tab-escape
|
|
/ null-character-escape
|
|
|
|
octal-digit = %x30-37 ; 0-7
|
|
|
|
hexadecimal-digit = digit / "a" / "b" / "c" / "d" / "e" / "f"
|
|
|
|
ascii-character-escape = %s"\x" octal-digit hexadecimal-digit
|
|
|
|
unicode-character-escape = %s"\u{" 1*6hexadecimal-digit "}"
|
|
|
|
format-string-element-not-brace = not-double-quote-or-backslash-or-brace
|
|
/ simple-character-escape
|
|
/ ascii-character-escape
|
|
/ unicode-character-escape
|
|
|
|
format-string-container = "{}"
|
|
|
|
format-string-open-brace = "{{"
|
|
|
|
format-string-close-brace = "}}"
|
|
|
|
format-string-element = format-string-element-not-brace
|
|
/ format-string-container
|
|
/ format-string-open-brace
|
|
/ format-string-close-brace
|
|
|
|
format-string = double-quote *format-string-element double-quote
|