feat: partial list support

- declare list variables with square brackets
- print list variables

tahini/app/src/main/java/com/tahini/lang/Expr.java

@@ -13,6 +13,7 @@ interface Visitor<R> {
     R visitTernaryExpr(Ternary expr);
     R visitVariableExpr(Variable expr);
     R visitLogicalExpr(Logical expr);
+    R visitTahiniListExpr(TahiniList expr);
   }
   static class Assign extends Expr {
     Assign(Token name, Expr value) {
@@ -142,6 +143,18 @@ <R> R accept(Visitor<R> visitor) {
     final Token operator;
     final Expr right;
   }
+  static class TahiniList extends Expr {
+    TahiniList(List<Expr> elements) {
+      this.elements = elements;
+    }
+
+    @Override
+    <R> R accept(Visitor<R> visitor) {
+      return visitor.visitTahiniListExpr(this);
+    }
+
+    final List<Expr> elements;
+  }
 
   abstract <R> R accept(Visitor<R> visitor);
 }

tahini/app/src/main/java/com/tahini/lang/Interpreter.java

@@ -76,6 +76,15 @@ private String stringify(Object object) {
         return object.toString();
     }
 
+    @Override
+    public Object visitTahiniListExpr(Expr.TahiniList expr) {
+        List<Object> tahiniList = new ArrayList<>();
+        for (Expr element : expr.elements) {
+            tahiniList.add(evaluate(element));
+        }
+        return tahiniList;
+    }
+
     @Override
     public Object visitLiteralExpr(Expr.Literal expr) {
         return expr.value;

tahini/app/src/main/java/com/tahini/lang/Parser.java

@@ -542,6 +542,17 @@ private Expr primary() {
             return new Expr.Grouping(expr);
         }
 
+        if (match(TokenType.LEFT_SQUARE)) {
+            List<Expr> elements = new ArrayList<>();
+            if (!check(TokenType.RIGHT_SQUARE)) {
+                do {
+                    elements.add(expression());
+                } while (match(TokenType.COMMA));
+            }
+            consume(TokenType.RIGHT_SQUARE, "Expect ']' after list elements.");
+            return new Expr.TahiniList(elements);
+        }
+
         // Error production for binary operator without left-hand operand
         if (match(TokenType.PLUS, TokenType.MINUS, TokenType.STAR, TokenType.SLASH, TokenType.EQUAL_EQUAL, TokenType.BANG_EQUAL, TokenType.GREATER, TokenType.GREATER_EQUAL, TokenType.LESS, TokenType.LESS_EQUAL)) {
             Token operator = previous();

tahini/app/src/main/java/com/tahini/lang/Scanner.java

@@ -73,6 +73,10 @@ private void scanToken() {
                 addToken(TokenType.LEFT_BRACE);
             case '}' ->
                 addToken(TokenType.RIGHT_BRACE);
+            case '[' ->
+                addToken(TokenType.LEFT_SQUARE);
+            case ']' ->
+                addToken(TokenType.RIGHT_SQUARE);
             case ',' ->
                 addToken(TokenType.COMMA);
             case '.' ->

tahini/app/src/main/java/com/tahini/lang/TokenType.java

@@ -2,7 +2,7 @@
 
 enum TokenType {
     // Single-character tokens.
-    LEFT_PAREN, RIGHT_PAREN, LEFT_BRACE, RIGHT_BRACE,
+    LEFT_PAREN, RIGHT_PAREN, LEFT_BRACE, RIGHT_BRACE, LEFT_SQUARE, RIGHT_SQUARE,
     COMMA, DOT, MINUS, PLUS, SEMICOLON, SLASH, STAR, QUESTION_MARK, COLON,
     // One or two character tokens.
     BANG, BANG_EQUAL,

tahini/app/src/main/java/com/tahini/tool/GenerateAst.java

@@ -23,7 +23,8 @@ public static void main(String[] args) throws IOException {
                 "Unary    : Token operator, Expr right",
                 "Ternary  : Expr condition, Expr left, Expr right",
                 "Variable : Token name",
-                "Logical  : Expr left, Token operator, Expr right"
+                "Logical  : Expr left, Token operator, Expr right",
+                "TahiniList     : List<Expr> elements"
         ));
 
         defineAst(outputDir, "Stmt", Arrays.asList(