From 15b331f4470a09955a65eeb1cc5eadb0b3e300b4 Mon Sep 17 00:00:00 2001
From: Sebastian Hugentobler <sebastian@vanwa.ch>
Date: Tue, 11 Feb 2025 14:09:52 +0100
Subject: [PATCH] pull interpreter value out into its own file

---
 rust/rox/src/interpreter.rs | 30 +------------------------
 rust/rox/src/lib.rs         |  3 ++-
 rust/rox/src/value.rs       | 45 +++++++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 30 deletions(-)
 create mode 100644 rust/rox/src/value.rs

diff --git a/rust/rox/src/interpreter.rs b/rust/rox/src/interpreter.rs
index 85f151f..f55ed54 100644
--- a/rust/rox/src/interpreter.rs
+++ b/rust/rox/src/interpreter.rs
@@ -3,6 +3,7 @@ use thiserror::Error;
 use crate::{
     expression::Expression,
     token::{Literal, Token, TokenType},
+    value::Value,
 };
 
 #[derive(Error, Debug)]
@@ -15,35 +16,6 @@ pub enum InterpreterError {
     BinaryOperatorUnknown(usize, String),
 }
 
-#[derive(Clone, Debug, PartialEq)]
-pub enum Value {
-    String(String),
-    Number(f64),
-    Boolean(bool),
-    Nil,
-}
-
-impl Value {
-    fn is_truthy(&self) -> bool {
-        match self {
-            Value::Nil => false,
-            Value::Boolean(b) => *b,
-            _ => true,
-        }
-    }
-}
-
-impl From<Literal> for Value {
-    fn from(value: Literal) -> Self {
-        match value {
-            Literal::String(x) => Value::String(x),
-            Literal::Number(x) => Value::Number(x),
-            Literal::Boolean(x) => Value::Boolean(x),
-            Literal::Nil => Value::Nil,
-        }
-    }
-}
-
 /// Try to evaluate an expression and return its result.
 pub fn evaluate(expression: Expression) -> Result<Value, InterpreterError> {
     match expression {
diff --git a/rust/rox/src/lib.rs b/rust/rox/src/lib.rs
index d185fb0..64b32bb 100644
--- a/rust/rox/src/lib.rs
+++ b/rust/rox/src/lib.rs
@@ -27,6 +27,7 @@ pub mod tokenizer {
     pub mod string;
     pub mod whitespace;
 }
+pub mod value;
 
 /// Read the source code in a file and scan it to tokens.
 pub fn compile(source: &Path) -> Result<(), io::Error> {
@@ -57,7 +58,7 @@ fn run(input: &str) {
     let tokens = scanner::tokenize(input);
     match parser::generate_ast(tokens) {
         Ok(ast) => match interpreter::evaluate(ast) {
-            Ok(value) => info!("{value:?}"),
+            Ok(value) => println!("{value}"),
             Err(e) => error!("{e}"),
         },
         Err(e) => error!("{e}"),
diff --git a/rust/rox/src/value.rs b/rust/rox/src/value.rs
new file mode 100644
index 0000000..5efcc64
--- /dev/null
+++ b/rust/rox/src/value.rs
@@ -0,0 +1,45 @@
+use std::fmt::Display;
+
+use crate::token::Literal;
+
+/// Concrete value in the interpreter.
+#[derive(Clone, Debug, PartialEq)]
+pub enum Value {
+    String(String),
+    Number(f64),
+    Boolean(bool),
+    Nil,
+}
+
+impl Display for Value {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Value::String(x) => write!(f, "{x}"),
+            Value::Number(x) => write!(f, "{x}"),
+            Value::Boolean(x) => write!(f, "{x}"),
+            Value::Nil => write!(f, "nil"),
+        }
+    }
+}
+
+impl Value {
+    /// Return false for nil or a false boolean, true otherwise.
+    pub fn is_truthy(&self) -> bool {
+        match self {
+            Value::Nil => false,
+            Value::Boolean(b) => *b,
+            _ => true,
+        }
+    }
+}
+
+impl From<Literal> for Value {
+    fn from(value: Literal) -> Self {
+        match value {
+            Literal::String(x) => Value::String(x),
+            Literal::Number(x) => Value::Number(x),
+            Literal::Boolean(x) => Value::Boolean(x),
+            Literal::Nil => Value::Nil,
+        }
+    }
+}