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copied!<p>Compare:</p> <pre><code>user> (:baz (:bar (:foo {:foo {:bar {:baz 123}}}))) 123 user> (java.io.BufferedReader. (java.io.FileReader. "foo.txt")) #<BufferedReader java.io.BufferedReader@6e1f8f> user> (vec (reverse (.split (.replaceAll (.toLowerCase "FOO,BAR,BAZ") "b" "x") ","))) ["xaz" "xar" "foo"] </code></pre> <p>to:</p> <pre><code>user> (-> {:foo {:bar {:baz 123}}} :foo :bar :baz) 123 user> (-> "foo.txt" java.io.FileReader. java.io.BufferedReader.) #<BufferedReader java.io.BufferedReader@7a6c34> user> (-> "FOO,BAR,BAZ" .toLowerCase (.replaceAll "b" "x") (.split ",") reverse vec) ["xaz" "xar" "foo"] </code></pre> <p><code>-></code> is used when you want a concise way to nest calls. It lets you list the calls in the order they'll be called rather than inside-out, which can be more readable. In the third example, notice how much distance is between some of the arguments and the function they belong to; <code>-></code> lets you group arguments and function calls a bit more cleanly. Because it's a macro it also works for Java calls, which is nice.</p> <p><code>-></code> isn't that powerful, it just saves you a few parens now and then. Using it or not is a question of style and readability.</p> <p>Look at the bottom of <a href="http://github.com/richhickey/clojure/blob/master/src/clj/clojure/zip.clj" rel="noreferrer">clojure.zip</a> for extreme examples of how this is helpful.</p> <pre><code>(-> dz next next next next next next next next next remove up (append-child 'e) root) </code></pre>

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