Add lib/std, compile_expression ()
diff --git a/src/lisp/lib/std.h b/src/lisp/lib/std.h
new file mode 100644
index 0000000..85d766c
--- /dev/null
+++ b/src/lisp/lib/std.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "../lisp.h"
+#include "../compiler.h"
+
+value_t l_plus (value_t a, value_t b);
+
+void add_function (struct environment *env, char *name, void *func, int nargs);
+void load_std (struct environment *env);