refactor(tazjin/rlox): Constructor for interpreter with globals r/2097

Change-Id: Id8242c22500c8e2781cc656d3faabb28d9bdf091
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2383
Reviewed-by: tazjin <mail@tazj.in>
Tested-by: BuildkiteCI

2 files changed, 21 insertions, 3 deletions

diff --git a/users/tazjin/rlox/src/interpreter.rs b/users/tazjin/rlox/src/interpreter.rs
index 2ddbab7e1f29..5944bdfec8d9 100644
--- a/users/tazjin/rlox/src/interpreter.rs
+++ b/users/tazjin/rlox/src/interpreter.rs
@@ -118,12 +118,30 @@ fn identifier_str<'a>(name: &'a scanner::Token) -> Result<&'a str, Error> {
     }
 }
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct Interpreter {
     env: Rc<RwLock<Environment>>,
 }
 
 impl Interpreter {
+    /// Create a new interpreter and configure the initial global
+    /// variable set.
+    pub fn create() -> Self {
+        let mut globals = HashMap::new();
+
+        globals.insert(
+            "clock".into(),
+            Value::Callable(Callable::Builtin(&builtins::Clock {})),
+        );
+
+        Interpreter {
+            env: Rc::new(RwLock::new(Environment {
+                enclosing: None,
+                values: globals,
+            })),
+        }
+    }
+
     // Environment modification helpers
     fn define_var(&mut self, name: &scanner::Token, value: Value) -> Result<(), Error> {
         self.env
diff --git a/users/tazjin/rlox/src/main.rs b/users/tazjin/rlox/src/main.rs
index c56d345862c9..8970349bfa69 100644
--- a/users/tazjin/rlox/src/main.rs
+++ b/users/tazjin/rlox/src/main.rs
@@ -25,14 +25,14 @@ fn main() {
 // Run Lox code from a file and print results to stdout
 fn run_file(file: &str) {
     let contents = fs::read_to_string(file).expect("failed to read the input file");
-    let mut lox = interpreter::Interpreter::default();
+    let mut lox = interpreter::Interpreter::create();
     run(&mut lox, &contents);
 }
 
 // Evaluate Lox code interactively in a shitty REPL.
 fn run_prompt() {
     let mut line = String::new();
-    let mut lox = interpreter::Interpreter::default();
+    let mut lox = interpreter::Interpreter::create();
 
     loop {
         print!("> ");