test(pratt): migrate parser example

A new feature 'unstable' publishes module internals for tests and
examples only. This isn't a general-purpose winnow crate, so keep it
private by default.

Refs: winnow-rs/winnow#622

Author: ssmendon

crates/dice_parse/Cargo.toml

@@ -6,3 +6,13 @@ edition = "2024"
 [dependencies]
 bumpalo = { version = "3.17.0", features = ["std"] }
 winnow = { version = "0.7.10", features = ["std"] }
+
+[features]
+unstable = []
+
+[dev-dependencies]
+
+[[example]]
+name = "pratt"
+test = true
+required-features = ["unstable"]

crates/dice_parse/examples/pratt/main.rs

@@ -0,0 +1,32 @@
+use std::io::BufRead;
+
+use winnow::prelude::*;
+
+mod parser;
+
+fn main() {
+    let stdin = std::io::stdin();
+    let mut handle = stdin.lock();
+    let mut buffer = String::new();
+
+    loop {
+        buffer.clear();
+        match handle.read_line(&mut buffer) {
+            Ok(0) => break, // eof
+            Ok(_) => parse(&buffer),
+            Err(why) => eprintln!("failed to read line: `{why}`"),
+        }
+    }
+}
+
+fn parse(input: &str) {
+    match parser::pratt_parser.parse(input) {
+        Ok(result) => {
+            println!("{result}");
+        }
+        Err(err) => {
+            eprintln!("FAILED");
+            eprintln!("{err}");
+        }
+    }
+}