can now parse prefix expressions!

src/ast/errors/error.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "token/token.hpp"
 #include "token/type.hpp"
 
 namespace ast::error {
@@ -12,6 +13,14 @@ namespace ast::error {
         explicit parser_error(const std::string& message): error(message) {}
     };
 
+    struct unkown_prefix : parser_error {
+        token::token prefix;
+
+        explicit unkown_prefix(token::token prefix, const std::string& message)
+            : parser_error(message),
+              prefix(prefix) {}
+    };
+
     struct expected_next : parser_error {
         token::type expected_type;
 

src/ast/expressions/prefix.cpp

@@ -0,0 +1,19 @@
+#include "prefix.hpp"
+
+#include "token/token.hpp"
+
+namespace ast {
+
+    prefix_expr::prefix_expr(token::token token, std::string op)
+        : token(std::move(token)),
+          op(op),
+          right(nullptr) {}
+
+    std::string prefix_expr::token_literal() const {
+        return token.literal;
+    }
+
+    std::string prefix_expr::str() const {
+        return token.literal + right->str();
+    }
+} // namespace ast

src/ast/expressions/prefix.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "ast/ast.hpp"
+#include "token/token.hpp"
+
+namespace ast {
+    struct prefix_expr : expression {
+        prefix_expr(token::token token, std::string op);
+        token::token token;
+        std::string op;
+        expression* right;
+
+        std::string token_literal() const override;
+        std::string str() const override;
+    };
+} // namespace ast