3.1.1 Returning special status codes

Besides returning a page by writing it to the current output stream, the server goal can raise an exception using throw/1 to generate special pages such as not_found, moved, etc. The defined exceptions are:

http_reply(+Reply, +HdrExtra)

Return a result page using http_reply/3. See http_reply/3 for details.

http_reply(+Reply)

Equivalent to http_reply(Reply,[]).

http(not_modified)

Equivalent to http_reply(not_modified,[]). This exception is for backward compatibility and can be used by the server to indicate the referenced resource has not been modified since it was requested last time.