PEG Grammars for Nom
nom-peg is a PEG (Parsing Expression Grammar) parser generator built on top of nom, using a syntax that is heavily inspired by LALRPOP.
Grammars defined with nom-peg can freely be mixed with other nom parsers.
Example
let arithmetic = grammar! {
parse: i64 = <expr> "="
expr: i64 = <l: product> "+" <r: expr> => { l + r }
| <l: product> "+" <r: expr> => { l - r }
| product
product: i64 = <l: value> "*" <r: product> => { l * r }
| <l: value> "/" <r: product> => { l / r }
| value
value: i64 = ("0"|"1"|"2"|"3"|"4"|"5"|"6"|"7"|"8"|"9")+ => { result.join("").parse::<i64>().unwrap() }
| "(" <expr> ")"
};
assert_eq!(arithmetic.parse("123="), Ok(("", 123 as i64)));
assert_eq!(arithmetic.parse("1+1="), Ok(("", 2 as i64)));
assert_eq!(arithmetic.parse("12+(3*7)="), Ok(("", 33 as i64)));