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<title>8.20 Empty variant types</title>
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<h2 class="section" id="s:empty-variants"><a class="section-anchor" href="#s:empty-variants" aria-hidden="true"></a>8.20 Empty variant types</h2>
<p>
(Introduced in 4.07.0)</p><div class="syntax"><table class="display dcenter"><tr class="c019"><td class="dcell"><table class="c001 cellpading0"><tr><td class="c018">
<a class="syntax" href="typedecl.html#type-representation"><span class="c010">type-representation</span></a></td><td class="c015">::=</td><td class="c017">
...
</td></tr>
<tr><td class="c018"> </td><td class="c015">∣</td><td class="c017"> <span class="c004">=</span> <span class="c004">|</span>
</td></tr>
</table></td></tr>
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This extension allows user to define empty variants.
Empty variant type can be eliminated by refutation case of pattern matching.
</p><div class="caml-example verbatim">
<div class="ocaml">
<div class="pre caml-input"> <span class="ocamlkeyword">type</span> t = |
<span class="ocamlkeyword">let</span> f (x: t) = <span class="ocamlkeyword">match</span> x <span class="ocamlkeyword">with</span> _ -> .</div></div>
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