Add support for variables in interpreter

src/compiler.rs

@@ -1,12 +1,13 @@
 use std::io;
 
-use interpreter::interpret;
+use interpreter::Interpreter;
 use parser::parse;
 use tokenizer::tokenize;
 
 mod ast;
 mod interpreter;
 mod parser;
+mod symtab;
 mod token;
 mod tokenizer;
 mod value;
@@ -18,10 +19,15 @@ pub fn compile(code: &str) {
 
 pub fn start_interpreter() {
     let lines = io::stdin().lines();
-
+    #[allow(clippy::manual_flatten)]
     for line in lines {
         if let Ok(code) = line {
-            println!("{}", interpret(&parse(&tokenize(&code))));
+            let tokens = tokenize(&code);
+            let ast = parse(&tokens);
+
+            let mut interpreter = Interpreter::new();
+            let val = interpreter.interpret(&ast);
+            println!("{}", val);
         }
     }
 }

src/compiler/interpreter.rs

@@ -1,44 +1,71 @@
+use std::collections::HashMap;
+
 use crate::compiler::{
     ast::Expression::{self, *},
+    symtab::SymTab,
     value::Value,
 };
 
-#[expect(unused_variables)]
+pub struct Interpreter<'source> {
-pub fn interpret(ast: &Expression) -> Value {
+    symbols: SymTab<'source>,
+}
+
+impl<'source> Interpreter<'source> {
+    pub fn new() -> Self {
+        Interpreter {
+            symbols: SymTab::new_global(),
+        }
+    }
+
+    pub fn interpret(&mut self, ast: &Expression<'source>) -> Value {
         match ast {
             EmptyLiteral(_) => Value::None(),
             IntLiteral(_, val) => Value::Int(*val),
             BoolLiteral(_, val) => Value::Bool(*val),
-        Identifier(_, _) => todo!(), // Variables are TODO
+            Identifier(_, name) => *self.symbols.get(name),
             UnaryOp(_, op, expr) => match *op {
-            "-" => -interpret(expr),
+                "-" => -self.interpret(expr),
-            "not" => !interpret(expr),
+                "not" => !self.interpret(expr),
                 _ => panic!("Unrecognized unary op {}", op),
             },
             BinaryOp(_, left, op, right) => match *op {
-            "+" => interpret(left) + interpret(right),
+                "+" => self.interpret(left) + self.interpret(right),
-            "*" => interpret(left) * interpret(right),
+                "*" => self.interpret(left) * self.interpret(right),
-            "-" => interpret(left) - interpret(right),
+                "-" => self.interpret(left) - self.interpret(right),
-            "/" => interpret(left) / interpret(right),
+                "/" => self.interpret(left) / self.interpret(right),
-            "%" => interpret(left) % interpret(right),
+                "%" => self.interpret(left) % self.interpret(right),
-            "==" => Value::Bool(interpret(left) == interpret(right)),
+                "==" => Value::Bool(self.interpret(left) == self.interpret(right)),
-            "!=" => Value::Bool(interpret(left) != interpret(right)),
+                "!=" => Value::Bool(self.interpret(left) != self.interpret(right)),
-            "<" => Value::Bool(interpret(left) < interpret(right)),
+                "<" => Value::Bool(self.interpret(left) < self.interpret(right)),
-            "<=" => Value::Bool(interpret(left) <= interpret(right)),
+                "<=" => Value::Bool(self.interpret(left) <= self.interpret(right)),
-            ">" => Value::Bool(interpret(left) > interpret(right)),
+                ">" => Value::Bool(self.interpret(left) > self.interpret(right)),
-            ">=" => Value::Bool(interpret(left) >= interpret(right)),
+                ">=" => Value::Bool(self.interpret(left) >= self.interpret(right)),
-            "and" => interpret(left).and(&interpret(right)),
+                "and" => self.interpret(left).and(&self.interpret(right)),
-            "or" => interpret(left).or(&interpret(right)),
+                "or" => self.interpret(left).or(&self.interpret(right)),
-            "=" => todo!(), // Variables are TODO
+                "=" => {
+                    if let Expression::Identifier(_, name) = **left {
+                        let val = self.interpret(right);
+                        *self.symbols.get(name) = val;
+                        val
+                    } else {
+                        panic!("Assignment must have identifier as left expr!");
+                    }
+                }
                 _ => panic!("Unrecognized binary op {}", op),
             },
-        VarDeclaration(_, name, expr) => todo!(), // Variables are TODO
+            VarDeclaration(_, name, expr) => {
+                let value = self.interpret(expr);
+                if self.symbols.locals.insert(name, value).is_some() {
+                    panic!("Variable {} already defined in this scope!", name)
+                }
+                Value::None()
+            }
             Conditional(_, condition_expr, then_expr, else_expr) => {
-            if let Value::Bool(condition) = interpret(condition_expr) {
+                if let Value::Bool(condition) = self.interpret(condition_expr) {
                     if condition {
-                    interpret(then_expr)
+                        self.interpret(then_expr)
                     } else if let Some(expr) = else_expr {
-                    interpret(expr)
+                        self.interpret(expr)
                     } else {
                         Value::None()
                     }
@@ -49,10 +76,10 @@ pub fn interpret(ast: &Expression) -> Value {
             While(_, condition, do_expr) => {
                 let mut val = Value::None();
                 loop {
-                let condition = interpret(condition);
+                    let condition = self.interpret(condition);
                     if let Value::Bool(cond) = condition {
                         if cond {
-                        val = interpret(do_expr);
+                            val = self.interpret(do_expr);
                         } else {
                             break;
                         }
@@ -64,11 +91,24 @@ pub fn interpret(ast: &Expression) -> Value {
             }
             FunCall(_, name, args) => todo!(), // Functions are TODO
             Block(_, expressions) => {
+                self.symbols = SymTab {
+                    locals: HashMap::new(),
+                    parent: Some(Box::new(std::mem::take(&mut self.symbols))),
+                };
+
                 let mut val = Value::None();
                 for expression in expressions {
-                val = interpret(expression);
+                    val = self.interpret(expression);
                 }
+
+                if let Some(symbols) = &mut self.symbols.parent {
+                    self.symbols = std::mem::take(symbols);
+                } else {
+                    panic!("Non-global symbol table without parent!");
+                }
+
                 val
             }
         }
+    }
 }

src/compiler/symtab.rs

@@ -0,0 +1,27 @@
+use crate::compiler::value::Value;
+use std::collections::HashMap;
+
+#[derive(Default)]
+pub struct SymTab<'source> {
+    pub locals: HashMap<&'source str, Value>,
+    pub parent: Option<Box<SymTab<'source>>>,
+}
+
+impl<'source> SymTab<'source> {
+    pub fn get(&mut self, symbol: &str) -> &mut Value {
+        if let Some(val) = self.locals.get_mut(symbol) {
+            val
+        } else if let Some(parent) = &mut self.parent {
+            parent.get(symbol)
+        } else {
+            panic!("No symbol {} found!", symbol);
+        }
+    }
+
+    pub fn new_global() -> SymTab<'source> {
+        SymTab {
+            locals: HashMap::new(),
+            parent: None,
+        }
+    }
+}

src/compiler/value.rs

@@ -3,7 +3,7 @@ use std::{
     ops::{Add, Div, Mul, Neg, Not, Rem, Sub},
 };
 
-#[derive(PartialEq, PartialOrd, Debug)]
+#[derive(PartialEq, PartialOrd, Debug, Copy, Clone)]
 pub enum Value {
     Int(i64),
     Bool(bool),