Chapter 7

src/interpreter.rs

@@ -0,0 +1,94 @@
+use std::io::Write;
+
+use crate::error::LoxError;
+use crate::lexer::{scan_tokens, Token};
+use crate::parser::parser::parse_tokens;
+
+pub fn interpreter_main() {
+    let args: Vec<String> = std::env::args().collect();
+
+    match args.len() {
+        1 => run_repl(),
+        2 => run_file(&args[1]),
+        _ => {
+            eprintln!("Usage: rlox [script]");
+            std::process::exit(64);
+        }
+    }
+}
+
+fn run_file(script_path: &str) {
+    let source_code = std::fs::read_to_string(script_path).unwrap_or_else(|err| {
+        eprintln!("Reading script file {} failed: {}", script_path, err);
+        std::process::exit(66);
+    });
+
+    if let Err(err) = run(&source_code) {
+        eprintln!("{}", err);
+        std::process::exit(65);
+    }
+}
+
+fn run_repl() {
+    let stdin = std::io::stdin();
+
+    'outer: loop {
+        let mut input_buf = String::new();
+
+        print!("> ");
+        std::io::stdout().flush().unwrap();
+
+        'inner: loop {
+            stdin.read_line(&mut input_buf).unwrap_or_else(|err| {
+                eprintln!("Could not read from stdin: {}", err);
+                std::process::exit(66);
+            });
+
+            let num_open_braces = (input_buf.matches('{').count() as i64) - (input_buf.matches('}').count() as i64);
+            let num_open_parens = (input_buf.matches('(').count() as i64) - (input_buf.matches(')').count() as i64);
+            let num_open_brackets = (input_buf.matches('[').count() as i64) - (input_buf.matches(']').count() as i64);
+
+            // all braces/parens/brackets closed => break
+            if num_open_braces == 0 && num_open_parens == 0 && num_open_brackets == 0 {
+                break 'inner;
+            }
+
+            // any braces/parens/brackets more closing than opening => break (will be parse error)
+            if num_open_braces < 0 || num_open_parens < 0 || num_open_brackets < 0 {
+                break 'inner;
+            }
+
+            print!("< ");
+            std::io::stdout().flush().unwrap();
+        }
+
+        input_buf = input_buf.trim().to_owned();
+
+        if input_buf.is_empty() || input_buf == "exit" || input_buf == "quit" {
+            break 'outer;
+        }
+
+        match run(&input_buf) {
+            Ok(()) => {}
+            Err(err) => eprintln!("{}", err),
+        }
+    }
+}
+
+fn run(code_string: &str) -> Result<(), LoxError> {
+    let tokens: Vec<Token> = scan_tokens(code_string)?;
+
+    /* let token_str = tokens
+        .iter()
+        .map(|token| format!("{token}"))
+        .collect::<Vec<String>>()
+        .join(" ");
+
+    println!("{token_str}"); */
+
+    let expr = parse_tokens(tokens)?;
+
+    println!("{expr}");
+
+    Ok(())
+}