Pratt Parser Optimisation

Cargo.toml

@@ -127,6 +127,11 @@ harness = false
 name = "cbor"
 harness = false
 
+[[bench]]
+name = "pratt"
+harness = false
+required-features = ["pratt"]
+
 [[example]]
 name = "nano_rust"
 required-features = ["label"]

benches/pratt.rs

@@ -0,0 +1,66 @@
+use chumsky::{pratt::*, prelude::*};
+use criterion::{criterion_group, criterion_main, Criterion};
+use std::hint::black_box;
+
+mod utils;
+
+static CORPUS: &str = include_str!("samples/pratt.txt");
+
+fn bench_pratt(c: &mut Criterion) {
+    c.bench_function("pratt", {
+        move |b| b.iter(|| black_box(parser().parse(CORPUS)).unwrap())
+    });
+}
+
+criterion_group!(
+    name = benches;
+    config = utils::make_criterion();
+    targets = bench_pratt
+);
+
+criterion_main!(benches);
+
+pub enum Expr {
+    Num(i64),
+    Neg(Box<Self>),
+    Fact(Box<Self>),
+    Pow(Box<Self>, Box<Self>),
+    Mul(Box<Self>, Box<Self>),
+    Div(Box<Self>, Box<Self>),
+    Rem(Box<Self>, Box<Self>),
+    Add(Box<Self>, Box<Self>),
+    Sub(Box<Self>, Box<Self>),
+}
+
+fn parser<'src>() -> impl Parser<'src, &'src str, Expr> {
+    recursive(|expr| {
+        let num = text::int(10).map(|s: &str| Expr::Num(s.parse().unwrap()));
+
+        let atom = choice((num, expr.delimited_by(just('('), just(')')))).padded();
+
+        let op = |c| just(c).padded();
+
+        atom.pratt((
+            postfix(10, op('!'), |x, _, _| Expr::Fact(Box::new(x))),
+            prefix(5, op('-'), |_, x, _| Expr::Neg(Box::new(x))),
+            infix(right(10), op('^'), |x, _, y, _| {
+                Expr::Pow(Box::new(x), Box::new(y))
+            }),
+            infix(left(8), op('*'), |x, _, y, _| {
+                Expr::Mul(Box::new(x), Box::new(y))
+            }),
+            infix(left(8), op('/'), |x, _, y, _| {
+                Expr::Div(Box::new(x), Box::new(y))
+            }),
+            infix(left(8), op('%'), |x, _, y, _| {
+                Expr::Rem(Box::new(x), Box::new(y))
+            }),
+            infix(left(2), op('+'), |x, _, y, _| {
+                Expr::Add(Box::new(x), Box::new(y))
+            }),
+            infix(left(2), op('-'), |x, _, y, _| {
+                Expr::Sub(Box::new(x), Box::new(y))
+            }),
+        ))
+    })
+}