15.3

rust/src/chunk.rs

@@ -5,6 +5,7 @@ use crate::value::Value;
 #[derive(Debug)]
 pub enum OpCode {
     Constant(usize),
+    Negate,
     Return,
 }
 
@@ -62,13 +63,13 @@ impl fmt::Display for DisassembledInstruction<'_> {
             write!(f, "{:>4} ", line)?;
         }
         match self.chunk.code[self.i] {
-            OpCode::Constant(constant) => {
+            OpCode::Constant(constant) => write!(
-                let value = self.chunk.constants[constant];
+                f,
-                write!(f, "{:<16} {:4} '{}'", "OP_CONSTANT", constant, value)?;
+                "{:<16} {:4} '{}'",
-            }
+                "OP_CONSTANT", constant, self.chunk.constants[constant]
-            OpCode::Return => {
+            )?,
-                write!(f, "OP_RETURN")?;
+            OpCode::Negate => write!(f, "OP_NEGATE")?,
-            }
+            OpCode::Return => write!(f, "OP_RETURN")?,
         }
 
         Ok(())

rust/src/main.rs

@@ -19,6 +19,7 @@ fn main() -> Result<()> {
     let mut chunk = Chunk::default();
 
     chunk.push_constant(1.2, 123);
+    chunk.push(OpCode::Negate, 123);
     chunk.push(OpCode::Return, 123);
 
     chunk.disassemble("test chunk");

rust/src/vm.rs

@@ -42,6 +42,10 @@ impl VM {
                     let value = self.chunk.constants[*constant];
                     self.push(value);
                 }
+                OpCode::Negate => {
+                    let value = self.pop();
+                    self.push(-value);
+                }
                 OpCode::Return => {
                     println!("{}", self.pop());
                     return Ok(());