expression

[Michael Lucy <MichaelGLucy@Gmail.com>]

Hey,

Is there any scheme expression that will just get ignored when the
scheme code is compiled?

I'm generating some code with a function like:

(define (gen-update-ab updatea updateb)
  `(begin
     ,(if updatea `(set! a (+ a 1)) `(donothing))
     ,(if updateb `(set! b (+ b 1)) `(donothing))))

And ideally I could replace the donothing function with something that
will get discarded during compilation.

There are alternatives, but they're pretty ugly (significantly moreso
in my actual code than they look below):

(define (gen-update-ab-2 updatea updateb)
  `(begin
     ,@(if updatea `((set! a (+ a 1))) `())
     ,@(if updateb `((set! b (+ b 1))) `())))

(define (gen-update-ab-3 updatea updateb)
  (filter (lambda (x) (not (null? x)))
          `(begin
             ,(if updatea `(set! a (+ a 1)) `())
             ,(if updateb `(set! b (+ b 1)) `()))))