Vendor things

third-party/vendor/codespan-reporting/examples/peg_calculator.rs

@@ -0,0 +1,68 @@
+//! An example of using `peg` with `codespan_reporting`.
+//!
+//! To run this example, execute the following command from the top level of
+//! this repository:
+//!
+//! ```sh
+//! cargo run --example peg_calculator
+//! ```
+
+use codespan_reporting::diagnostic::{Diagnostic, Label};
+use codespan_reporting::files::SimpleFile;
+use codespan_reporting::term;
+use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
+use rustyline::error::ReadlineError;
+use rustyline::Editor;
+
+peg::parser! {
+    grammar arithmetic() for str {
+        rule number() -> i64
+            = n:$(['0'..='9']+) { n.parse().unwrap() }
+
+        pub rule calculate() -> i64 = precedence!{
+            x:(@) "+" y:@ { x + y }
+            x:(@) "-" y:@ { x - y }
+                  "-" v:@ { - v }
+            --
+            x:(@) "*" y:@ { x * y }
+            x:(@) "/" y:@ { x / y }
+            --
+            x:@   "^" y:(@) { i64::pow(x, y as u32) }
+            v:@   "!"       { (1..v+1).product() }
+            --
+            "(" v:calculate() ")" { v }
+            n:number() { n }
+        }
+    }
+}
+
+fn main() -> anyhow::Result<()> {
+    let writer = StandardStream::stderr(ColorChoice::Always);
+    let config = codespan_reporting::term::Config::default();
+    let mut editor = Editor::<()>::new();
+
+    loop {
+        let line = match editor.readline("> ") {
+            Ok(line) => line,
+            Err(ReadlineError::Interrupted) | Err(ReadlineError::Eof) => return Ok(()),
+            Err(error) => return Err(error.into()),
+        };
+
+        match arithmetic::calculate(&line) {
+            Ok(number) => println!("{}", number),
+            Err(error) => {
+                let file = SimpleFile::new("<repl>", line);
+
+                let start = error.location.offset;
+                let diagnostic = Diagnostic::error()
+                    .with_message("parse error")
+                    .with_labels(vec![
+                        Label::primary((), start..start).with_message("parse error")
+                    ])
+                    .with_notes(vec![format!("expected: {}", error.expected)]);
+
+                term::emit(&mut writer.lock(), &config, &file, &diagnostic)?;
+            }
+        }
+    }
+}