Removing keys and values from map

Question

I have a map that looks like this:

{\a [\h] 
 \h [\w \w]
 \i [\w \h \t]
 \p [\t \u \h \a]
 \s [\t \a \t \t \i \w \h]
 \t [\a]
 \u [\t \t \s]
 \w []}

I want to remove e.g. \w from both keys and values. i.e. leaving this

{\a [\h] 
 \h []
 \i [\h \t]
 \p [\t \u \h \a]
 \s [\t \a \t \t \i \h]
 \t [\a]
 \u [\t \t \s]}

Notice, the \w key has gone and \w has gone from all the values!

Right now I have this, which works, but I'm sure there must be a better, more Clojurey way!

(defn remove-last [last cmap]
  (reduce-kv (fn [acc k v]
               (if (empty? v)
                 acc
                 (into acc {k (vec (filter #(not= % last) v))}))) {} cmap))

The key to remove will always be an empty vector.

How can I do this better?

Answer 1

I find your solution quite idiomatic. The requirement is unusual enough, that I immediately think reduce. Your call to empty? is not according to your spec, though. You'd have to test for the key k being = to last.

Also, I wouldn't use the name last here. It clashes with a name that is already present.

A very similar alternative would be

(defn remove-all-of [it m] 
  (reduce
   (fn [acc [k v]] 
     (if (not= it k)
       (assoc acc
              k
              (into (empty v)
                    (filter #(not= it %) v)))
       acc))
   {}
   m))

This also allows you to have some other seqable thing than vectors as values by using (empty v).