The Demo Page created in the Generating HTML lesson could have been created by a static file served by a conventional Web server, such as Apache. And in fact CL-HTTP can serve static files too.
But CL-HTTP really comes into its own when you want to create dynamic, interactive Web pages whose content changes.
The next example gives a light-hearted example illustrating how this works.
First we create a couple of routines to help. The first one, random-elt, returns a random element of a list:
(defun random-elt (list) (elt list (random (length list))))
Using this we define a random-aphorism program:
(defun aphorism (stream) "Write a random aphorism to stream." (format stream "~a ~a." (random-elt '("Many hands make" "Too many cooks spoil" "A stitch in time saves" "All work and no play makes" "Money is")) (random-elt '("light work" "the broth" "nine" "Jack a dull boy" "the root of all evil"))))
Here's the routine to create the page:
(defun write-aphorism (url stream) "Display a random aphorism." (with-page (url stream "Aphorism of the Day") (with-paragraph (:stream stream) (aphorism stream))))
Finally, we export the URL using export-url:
(export-url "http://localhost:8000/aphorism.html" :computed :response-function 'write-aphorism)
Each time we access the page a new aphorism is generated:
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