Hi,

I'd like to add attributes to SXML elements conditionally, but I don't 
see how.

I'm looking for a hypothetical "if*" that allows me to do the following:

(define* (special-input #:key name (required? #true))
   "Return an SXHTML INPUT element for typing text."
   `(input
     (@ (type "text")
        (name ,name)
        ,(if* required? '(required "")))))

The built-in "if" doesn't work here because it will return 
#<unspecified> when the condition is false, which is not an acceptable 
attribute. I'm not aware of any value that can be returned in an "else" 
expression that would mean "nothing" to SXML; the empty list is not it:

   ,(if required? '(required "") '())

I'm hoping to find something better than the following workaround:

(define* (special-input #:key name (required? #true))
   "Return an SXHTML INPUT element for typing text."
   (if required?
       `(input (@ (type "text") (name ,name) (required "")))
       `(input (@ (type "text") (name ,name)))))

Any ideas?

-- 
Luis Felipe López Acevedo
https://luis-felipe.gitlab.io/