dex.html#type-t">t</a></span> <span>&#45;&gt;</span> <span>f:<span>(<span class="type-var">'a</span> <span>&#45;&gt;</span> <span>[ <span>`Fst of <span class="type-var">'b</span></span> <span><span>| `Snd</span> of <span class="type-var">'c</span></span> <span><span>| `Trd</span> of <span class="type-var">'d</span></span> ]</span>)</span></span> <span>&#45;&gt;</span> <span><span class="type-var">'b</span> <a href="index.html#type-t">t</a></span> * <span><span class="type-var">'c</span> <a href="index.html#