 <p>Using Racket:</p> <pre><code>(for/sum ([image image-list]) (image-height image)) </code></pre> <p>or</p> <pre><code>(foldl (lambda (image sum) (+ (image-height image) sum)) 0 image-list) </code></pre> <p>or</p> <pre><code>(apply + (map image-height image-list)) </code></pre>