Reposition HTML to the receiving Id. The html_post//2 call
processes HTML using html//1. Embedded \-commands are executed
by mailman/1 from print_html/1 or html_print_length/2. These
commands are called in the calling context of the html_post//2
call.
A typical usage scenario is to get required CSS links in the
document head in a reusable fashion. First, we define css//1 as:
css(URL) -->
html_post(css,
link([ type('text/css'),
rel('stylesheet'),
href(URL)
])).
Next we insert the unique CSS links, in the pagehead using the
following call to reply_html_page/2:
reply_html_page([ title(...),
\html_receive(css)
],
...)
