<p><code>unsplit</code> is an arrow that takes a pair of values and combines them to return a single value:</p>
<preclass="sourceCode"><codeclass="sourceCode haskell"><spanclass="ot">unsplit </span><spanclass="ot">::</span> (<spanclass="dt">Arrow</span> a) <spanclass="ot">=></span> (b <spanclass="ot">-></span> c <spanclass="ot">-></span> d) <spanclass="ot">-></span> a (b, c) d<br/>unsplit <spanclass="fu">=</span> arr <spanclass="fu">.</span><spanclass="fu">uncurry</span><br/><spanclass="co">-- arr (\op (x,y) -> x `op` y) </span></code></pre>
<p><code>(***)</code> combines two arrows into a new arrow by running the two arrows on a pair of values (one arrow on the first item of the pair and one arrow on the second item of the pair).</p>
<pre><code>f *** g = first f >>> second g