extern type ip;
{{An IP address}}
+extern type your_ip;
+extern val your_ip_to_ip : your_ip -> ip;
+{{An IP address that you're authorized to use; e.g., for an SSL web host}}
+
extern type host;
{{A hostname; that is, (more or less) an alphanumeric string}}
{{A filesystem path that you're allowed to write to.
The set of permitted values is generated from a set of roots by closing it
under the subdirectory relation.}}
+extern val end_in_slash : your_path -> your_path;
+{{Add a slash at the end of a path, if there isn't one already.}}
extern type readable_path;
{{Like [your_path], but also includes some paths that everyone is allowed to