title: Assoc-if in Clojure
body: <p>Is there an "assoc-if" function in the Clojure library? I.e if a value is truthy, update a map with a given key value. I've tried to find something to this effect, but came up lacking.</p>
  
  <pre><code>(defn assoc-if
    [m key value]
    (if value (assoc m key value) m))
  </code></pre>