[plt-scheme] <select multiple> ... </select> as an xexpr

> > How would I write something like this using xexpr?  The problem being
> > that MULTIPLE doesn't have an ="..." attatched to it.
> >
> > <SELECT NAME="toppings" MULTIPLE SIZE=5>

For what it's worth, HtmlPrag's SHTML takes a liberty with SXML to
permit this HTML anachronism of element attributes defined with null
values:

(html->shtml "<select name=\"toppings\" multiple size=\"5\">...</select>")
==> (*TOP* (select (@ (name "toppings") (multiple) (size "5")) "..."))

(shtml->html '((select (@ (name "toppings") (multiple) (size "5")) "...")))
==> "<select name=\"toppings\" multiple size=\"5\">...</select>"

HtmlPrag also supports "#t" for the element null value, and that's
probably what the next version of HtmlPrag will move to as the official
way to do this.