diff --git a/compiler/CMakeLists.txt b/compiler/CMakeLists.txt
index bf37d8e..1e8dd60 100644
--- a/compiler/CMakeLists.txt
+++ b/compiler/CMakeLists.txt
@@ -1,9 +1,16 @@
 add_library(caioc_compiler STATIC
+	parser.cxx
 )
 
 target_sources(caioc_compiler
 	PUBLIC
 	FILE_SET caioc_compiler_modules TYPE CXX_MODULES FILES
+		declaration.ixx
+		expression.ixx
+		parser.ixx
+		program.ixx
+		statement.ixx
 		token.ixx
+
 )
 target_compile_options(caioc_compiler PUBLIC -freflection -fcontracts -fcontract-evaluation-semantic=enforce)
diff --git a/compiler/declaration.ixx b/compiler/declaration.ixx
index e69de29..b2c9c77 100644
--- a/compiler/declaration.ixx
+++ b/compiler/declaration.ixx
@@ -0,0 +1,58 @@
+export module caioc.declaration;
+
+import std;
+
+import caioc.statement;
+import caioc.expression;
+
+namespace caioc {
+
+export struct declaration {
+	virtual ~declaration() = default;
+};
+
+export struct function_declaration : declaration {
+	struct argument {
+		std::string name;
+		std::string type_name;
+	};
+
+	std::string name;
+	std::vector<argument> arguments;
+	std::string return_type;
+	std::unique_ptr<block_statement> body;
+};
+
+}  // namespace caioc
+
+export template <>
+struct std::formatter<caioc::function_declaration> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::function_declaration& d, std::format_context& ctx) const {
+		auto out = std::format_to(ctx.out(), "Function({}, args: [", d.name);
+		bool first = true;
+		for (const auto& arg : d.arguments) {
+			if (!first) {
+				out = std::format_to(out, ", ");
+			}
+			first = false;
+			out = std::format_to(out, "{}", arg);
+		}
+		out = std::format_to(out, "], return_type: {}", d.return_type);
+		out = d.body ? std::format_to(out, ", body: {}", *d.body) : std::format_to(out, ", body: <null>");
+		return std::format_to(out, ")");
+	}
+};
+
+export template <>
+struct std::formatter<caioc::declaration> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::declaration& d, std::format_context& ctx) const {
+		if (auto* p = dynamic_cast<const caioc::function_declaration*>(&d)) {
+			return std::format_to(ctx.out(), "{}", *p);
+		}
+		return std::format_to(ctx.out(), "<unknown declaration>");
+	}
+};
diff --git a/compiler/expression.ixx b/compiler/expression.ixx
index 8aa44df..84fd57f 100644
--- a/compiler/expression.ixx
+++ b/compiler/expression.ixx
@@ -5,7 +5,7 @@ import std;
 namespace caioc {
 
 export struct expression {
-	virtual expression() = default;
+	virtual ~expression() = default;
 };
 
 export struct int_literal_expression : expression {
@@ -20,7 +20,7 @@ export struct string_literal_expression : expression {
 
 export struct identifier_expression : expression {
 	std::string name;
-}
+};
 
 export struct call_expression : expression {
 	std::unique_ptr<expression> callee;
@@ -28,3 +28,84 @@ export struct call_expression : expression {
 };
 
 }  // namespace caioc
+
+export template <>
+struct std::formatter<caioc::int_literal_expression> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::int_literal_expression& e, std::format_context& ctx) const {
+		return std::format_to(ctx.out(), "IntLiteral({})", e.value);
+	}
+};
+
+export template <>
+struct std::formatter<caioc::bool_literal_expression> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::bool_literal_expression& e, std::format_context& ctx) const {
+		return std::format_to(ctx.out(), "BoolLiteral({})", e.value);
+	}
+};
+
+export template <>
+struct std::formatter<caioc::string_literal_expression> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::string_literal_expression& e, std::format_context& ctx) const {
+		return std::format_to(ctx.out(), "StringLiteral(\"{}\")", e.value);
+	}
+};
+
+export template <>
+struct std::formatter<caioc::identifier_expression> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::identifier_expression& e, std::format_context& ctx) const {
+		return std::format_to(ctx.out(), "Identifier({})", e.name);
+	}
+};
+
+export template <>
+struct std::formatter<caioc::expression> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	std::format_context::iterator format(const caioc::expression& e, std::format_context& ctx) const;
+};
+
+export template <>
+struct std::formatter<caioc::call_expression> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	std::format_context::iterator format(const caioc::call_expression& e, std::format_context& ctx) const;
+};
+
+inline std::format_context::iterator std::formatter<caioc::expression>::format(const caioc::expression& e,
+																			   std::format_context& ctx) const {
+	if (auto* p = dynamic_cast<const caioc::int_literal_expression*>(&e)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::bool_literal_expression*>(&e)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::string_literal_expression*>(&e)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::identifier_expression*>(&e)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::call_expression*>(&e)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	return std::format_to(ctx.out(), "<unknown expression>");
+}
+
+inline std::format_context::iterator std::formatter<caioc::call_expression>::format(const caioc::call_expression& e,
+																					std::format_context& ctx) const {
+	auto out = std::format_to(ctx.out(), "Call(");
+	out = e.callee ? std::format_to(out, "{}", *e.callee) : std::format_to(out, "<null>");
+	for (const auto& arg : e.args) {
+		out = std::format_to(out, ", ");
+		out = arg ? std::format_to(out, "{}", *arg) : std::format_to(out, "<null>");
+	}
+	return std::format_to(out, ")");
+}
diff --git a/compiler/parser.cxx b/compiler/parser.cxx
new file mode 100644
index 0000000..3d0462f
--- /dev/null
+++ b/compiler/parser.cxx
@@ -0,0 +1,14 @@
+module caioc.parser;
+
+import std;
+
+import caioc.program;
+import caioc.token;
+
+namespace caioc {
+
+class parser {};
+
+program_module parse(std::span<const token> tokens) { return {}; }
+
+}  // namespace caioc
diff --git a/compiler/parser.ixx b/compiler/parser.ixx
new file mode 100644
index 0000000..f962eb8
--- /dev/null
+++ b/compiler/parser.ixx
@@ -0,0 +1,10 @@
+export module caioc.parser;
+
+import std;
+
+import caioc.program;
+import caioc.token;
+
+namespace caioc {
+export [[nodiscard]] program_module parse(std::span<const token> tokens);
+}
diff --git a/compiler/program.ixx b/compiler/program.ixx
new file mode 100644
index 0000000..541912a
--- /dev/null
+++ b/compiler/program.ixx
@@ -0,0 +1,20 @@
+export module caioc.program;
+
+import std;
+
+import caioc.declaration;
+
+namespace caioc {
+
+export struct program_module {
+	std::vector<std::unique_ptr<declaration>> declarations;
+};
+
+}  // namespace caioc
+
+export template <>
+struct std::formatter<caioc::program_module> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::program_module& s, std::format_context& ctx) const {}
+};
diff --git a/compiler/statement.ixx b/compiler/statement.ixx
index e69de29..1f4ffec 100644
--- a/compiler/statement.ixx
+++ b/compiler/statement.ixx
@@ -0,0 +1,157 @@
+export module caioc.statement;
+
+import std;
+
+import caioc.expression;
+
+namespace caioc {
+export struct statement {
+	virtual ~statement() = default;
+};
+
+export struct return_statement : statement {
+	std::unique_ptr<expression> value;
+};
+
+export struct expression_statement : statement {
+	std::unique_ptr<expression> value;
+};
+
+export struct block_statement : statement {
+	std::vector<std::unique_ptr<statement>> statements;
+};
+
+export struct if_statement : statement {
+	std::unique_ptr<expression> condition;
+	std::unique_ptr<statement> then_branch;
+	std::unique_ptr<statement> else_branch;
+};
+
+export struct while_statement : statement {
+	std::unique_ptr<expression> condition;
+	std::unique_ptr<statement> body;
+};
+
+export struct let_statement : statement {
+	std::string name;
+	std::string type_name;
+	std::unique_ptr<expression> init;
+};
+
+}  // namespace caioc
+
+export template <>
+struct std::formatter<caioc::return_statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::return_statement& s, std::format_context& ctx) const {
+		return s.value ? std::format_to(ctx.out(), "Return({})", *s.value) : std::format_to(ctx.out(), "Return()");
+	}
+};
+
+export template <>
+struct std::formatter<caioc::expression_statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::expression_statement& s, std::format_context& ctx) const {
+		return s.value ? std::format_to(ctx.out(), "ExprStmt({})", *s.value)
+					   : std::format_to(ctx.out(), "ExprStmt(<null>)");
+	}
+};
+
+export template <>
+struct std::formatter<caioc::let_statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	auto format(const caioc::let_statement& s, std::format_context& ctx) const {
+		auto out = std::format_to(ctx.out(), "Let({}: {}", s.name, s.type_name);
+		out = s.init ? std::format_to(out, " = {}", *s.init) : out;
+		return std::format_to(out, ")");
+	}
+};
+
+// --- mutually-referencing cluster: declared here, defined out-of-line below ---
+
+export template <>
+struct std::formatter<caioc::statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	std::format_context::iterator format(const caioc::statement& s, std::format_context& ctx) const;
+};
+
+export template <>
+struct std::formatter<caioc::block_statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	std::format_context::iterator format(const caioc::block_statement& s, std::format_context& ctx) const;
+};
+
+export template <>
+struct std::formatter<caioc::if_statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	std::format_context::iterator format(const caioc::if_statement& s, std::format_context& ctx) const;
+};
+
+export template <>
+struct std::formatter<caioc::while_statement> {
+	constexpr auto parse(std::format_parse_context& ctx) { return ctx.begin(); }
+
+	std::format_context::iterator format(const caioc::while_statement& s, std::format_context& ctx) const;
+};
+
+inline std::format_context::iterator std::formatter<caioc::statement>::format(const caioc::statement& s,
+																			  std::format_context& ctx) const {
+	if (auto* p = dynamic_cast<const caioc::return_statement*>(&s)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::expression_statement*>(&s)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::block_statement*>(&s)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::if_statement*>(&s)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::while_statement*>(&s)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	if (auto* p = dynamic_cast<const caioc::let_statement*>(&s)) {
+		return std::format_to(ctx.out(), "{}", *p);
+	}
+	return std::format_to(ctx.out(), "<unknown statement>");
+}
+
+inline std::format_context::iterator std::formatter<caioc::block_statement>::format(const caioc::block_statement& s,
+																					std::format_context& ctx) const {
+	auto out = std::format_to(ctx.out(), "Block[");
+	bool first = true;
+	for (const auto& stmt : s.statements) {
+		if (!first) {
+			out = std::format_to(out, ", ");
+		}
+		first = false;
+		out = stmt ? std::format_to(out, "{}", *stmt) : std::format_to(out, "<null>");
+	}
+	return std::format_to(out, "]");
+}
+
+inline std::format_context::iterator std::formatter<caioc::if_statement>::format(const caioc::if_statement& s,
+																				 std::format_context& ctx) const {
+	auto out = std::format_to(ctx.out(),
+							  "If({}, then: ", s.condition ? std::format("{}", *s.condition) : std::string("<null>"));
+	out = s.then_branch ? std::format_to(out, "{}", *s.then_branch) : std::format_to(out, "<null>");
+	if (s.else_branch) {
+		out = std::format_to(out, ", else: {}", *s.else_branch);
+	}
+	return std::format_to(out, ")");
+}
+
+inline std::format_context::iterator std::formatter<caioc::while_statement>::format(const caioc::while_statement& s,
+																					std::format_context& ctx) const {
+	auto out =
+		std::format_to(ctx.out(), "While({}, ", s.condition ? std::format("{}", *s.condition) : std::string("<null>"));
+	out = s.body ? std::format_to(out, "{}", *s.body) : std::format_to(out, "<null>");
+	return std::format_to(out, ")");
+}
diff --git a/driver/main.cxx b/driver/main.cxx
index 7557911..0d905c0 100644
--- a/driver/main.cxx
+++ b/driver/main.cxx
@@ -2,6 +2,7 @@ import std;
 
 import caioc.utils;
 import caioc.frontend.tokenizer;
+import caioc.parser;
 
 auto main(int argc, char** argv) -> int {
 	if (argc < 2) {
@@ -20,9 +21,11 @@ auto main(int argc, char** argv) -> int {
 		return -1;
 	}
 
-	for (const auto token : tokens) {
+	for (const auto& token : tokens) {
 		std::println("{}: {} @ {}:{}", caioc::enum_to_string(token.type), token.backing, token.line, token.column);
 	}
 
+	const auto program = caioc::parse(tokens);
+
 	return 0;
 }