[rlox] Add trace to repl

rlox/src/main.rs

@@ -11,12 +11,15 @@ use vm::VM;
 fn repl() {
     let mut buffer = String::new();
 
+    let do_trace = env::var("LOX_TRACE").is_ok();
+
     loop {
         match io::stdin().read_line(&mut buffer) {
             Ok(_) => {
                 let mut chunk = Chunk::new();
                 lc::compile(buffer.as_str(), &mut chunk);
                 let mut vm = VM::new();
+                vm.set_trace(do_trace);
                 let result = vm.run(&chunk);
                 println!("{:?}", result);
                 buffer.clear();

rlox/src/vm.rs

@@ -23,6 +23,10 @@ impl VM {
         }
     }
 
+    pub fn set_trace(&mut self, trace: bool) {
+        self.trace = trace;
+    }
+
     fn runtime_err(&self, msg: &'static str) -> VMError {
         VMError::Runtime(msg.into(), self.pc)
     }