Interpreter - Initial environment implementation

src/interpreter/environment.rs

@@ -0,0 +1,29 @@
+use std::collections::HashMap;
+
+use crate::{errors::InterpreterError, tokens::Token};
+
+use super::Value;
+
+/// The execution environment.
+#[derive(Debug, Default)]
+pub struct Environment {
+    values: HashMap<String, Value>,
+}
+
+impl Environment {
+    /// Define a new variable.
+    pub fn define(&mut self, name: String, value: Value) {
+        self.values.insert(name, value);
+    }
+
+    /// Get the value of a variable.
+    pub fn get(&self, name: &Token) -> Result<Value, InterpreterError> {
+        match self.values.get(&name.lexeme as &str) {
+            None => Err(InterpreterError::new(
+                name,
+                &format!("undefined variable '{}'", name.lexeme),
+            )),
+            Some(value) => Ok(value.clone()),
+        }
+    }
+}