9 releases
0.4.0 | Sep 19, 2024 |
---|---|
0.3.1 | Jul 9, 2024 |
0.3.0 | May 8, 2022 |
0.2.2 | Apr 27, 2022 |
0.1.1 | Jan 31, 2022 |
#1769 in Procedural macros
4,909 downloads per month
Used in 2 crates
(via databend-common-ast)
30KB
542 lines
nom-rule
A procedural macro for writing nom parsers using a grammar-like syntax.
Overview
The nom-rule
crate provides the rule!
macro, which allows you to define nom parsers using a domain-specific language (DSL) that resembles grammar rules. This makes your parsers more readable and easier to maintain.
Features
- Define parsers using a grammar-like syntax.
- Integrates seamlessly with
nom
combinators. - Supports sequences, choices, repetitions, optional parsing, and more.
Usage
use nom_rule::rule;
// Define your match functions
fn match_text<'a>(text: &'a str) -> impl FnMut(Input<'a>) -> IResult<Input<'a>, &'a Token<'a>> {
// Implementation
}
fn match_token<'a>(kind: TokenKind) -> impl FnMut(Input<'a>) -> IResult<Input<'a>, &'a Token<'a>> {
// Implementation
}
fn ident<'a>(input: Input<'a>) -> IResult<Input<'a>, &str> {
// Implementation
}
// Use the `rule!` macro
let mut parser = rule!(
CREATE ~ TABLE ~ #ident ~ ^"(" ~ (#ident ~ #ident ~ ","?)* ~ ")" ~ ";"
: "CREATE TABLE statement"
);
Syntax
The rule!
macro follows these rules:
Syntax | Description | Expanded to | Operator Precedence |
---|---|---|---|
TOKEN |
Matches a token by kind. | match_token(TOKEN) |
- |
"(" |
Matches a token by its text. | match_text("(") |
- |
#fn_name |
Calls an external nom parser function fn_name . |
fn_name |
- |
#fn_name(a, b, c) |
Calls an external nom parser function fn_name with arguments. |
fn_name(a, b, c) |
- |
a ~ b ~ c |
Sequences parsers a , b , and c . |
nom::sequence::tuple((a, b, c)) |
3 (Left Associative) |
a+ |
One or more repetitions. | nom::multi::many1(a) |
4 (Postfix) |
a* |
Zero or more repetitions. | nom::multi::many0(a) |
4 (Postfix) |
a? |
Optional parser. | nom::combinator::opt(a) |
4 (Postfix) |
a | b | c |
Choice between parsers a , b , and c . |
nom::branch::alt((a, b, c)) |
1 (Left Associative) |
&a |
Peeks at parser a without consuming input. |
nom::combinator::peek(a) |
5 (Prefix) |
!a |
Negative lookahead for parser a . |
nom::combinator::not(a) |
5 (Prefix) |
^a |
Cuts the parser a . |
nom::combinator::cut(a) |
5 (Prefix) |
... : "description" |
Adds a context description for error reporting. | nom::error::context("description", a) |
2 (Postfix) |
Example
See the sqlparser.rs
file for a complete example parsing a simplified SQL CREATE TABLE
statement.
Dependencies
~1.1–1.8MB
~36K SLoC