[rlox] Add repl

rlox/src/main.rs

@@ -3,28 +3,43 @@ mod lc;
 mod vm;
 
 use std::env;
+use std::io;
+
+use bc::Chunk;
+use vm::VM;
+use crate::vm::VMError;
 
 fn repl() {
+    let mut buffer = String::new();
 
+    loop {
+        match io::stdin().read_line(&mut buffer) {
+            Ok(n) => {
+                let mut chunk = Chunk::new();
+                lc::compile(buffer.as_str(), &mut chunk);
+                let mut vm = VM::new();
+                let result = vm.run(&chunk);
+                println!("{:?}", result);
+                buffer.clear();
+            },
+            Err(error) => todo!()
+        }
+    }
 }
 
 fn run_file() {
-
+    todo!()
 }
 
 fn main() {
-
     let num_args = env::args().len();
-    let mut chunk = bc::Chunk::new();
-
-    lc::compile("print(1+2*3)", &mut chunk);
 
     if num_args == 1 {
-        repl();
+        repl()
     } else if num_args == 2 {
-        run_file();
+        run_file()
     } else {
-        println!("Usage: rlox [path]");
+        println!("Usage: rlox [path]")
     }
 }
 

rlox/src/vm.rs

@@ -1,3 +1,4 @@
+use std::ops::Not;
 use crate::bc::{Chunk, Op, TraceInfo, Value};
 
 pub struct VM {
@@ -35,7 +36,7 @@ impl VM {
             .ok_or_else(|| self.runtime_err("Attempt to pop of empty stack."))
     }
 
-    pub fn run(&mut self, chunk: &Chunk) -> Result<(), VMError> {
+    pub fn run(&mut self, chunk: &Chunk) -> Result<Option<Value>, VMError> {
         while self.pc < chunk.code.len() {
             let instr = chunk.code[self.pc];
             self.pc += 1;
@@ -79,7 +80,7 @@ impl VM {
             }
         }
 
-        Ok(())
+        Ok(self.stack.is_empty().not().then_some(self.stack[self.stack.len() - 1]))
     }
 }