Crate nom_rule

A procedural macro crate for writing nom parsers using a grammar-like syntax.

The nom-rule crate provides the rule! macro, which allows you to define parsers in a DSL similar to grammar rules. This improves readability and maintainability.

Syntax

The 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.	((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

use nom_rule::rule;
use nom::IResult;

// 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"
);

Macros

rule

A procedural macro for writing nom parsers using a grammar-like syntax.