default

[macro] default x test alt

(mac default (x test alt)
  (w/uniq gx
    `(let ,gx ,x
       (if (,test ,gx) ,gx ,alt))))

comment: a. I don't see this macro defined in arc. b. why a macro? I would define it as a function as this:

(def default (x test alt)
   (if (test x) x alt))

This is based on arc0. Probably it's removed in arc1; I haven't checked it yet.