init ast

src/ast/mod.rs

@@ -0,0 +1,38 @@
+trait NodeTrait {
+    fn token_literal(&self) -> String;
+}
+
+trait StatementTrait: NodeTrait {
+    fn statement_node(&self);
+}
+
+trait ExpressionTrait: NodeTrait {
+    fn expression_node(&self);
+}
+
+struct Statement {
+    //
+}
+impl NodeTrait for Statement {
+    fn token_literal(&self) -> String {
+        todo!()
+    }
+}
+
+impl StatementTrait for Statement {
+    fn statement_node(&self) {}
+}
+
+struct Program {
+    statements: Vec<Statement>,
+}
+
+impl NodeTrait for Program {
+    fn token_literal(&self) -> String {
+        if self.statements.is_empty() {
+            self.statements[0].token_literal()
+        } else {
+            String::new()
+        }
+    }
+}

src/main.rs

@@ -1,3 +1,4 @@
+mod ast;
 mod lexer;
 mod repl;
 mod token;