lass="type">A</span></code></p></h3><div class="doc"><p>Fold by mapping the contained value into some monoidal type and reducing with that monoid.</p></div></div><div class="field "><a name="isLeft"></a><h3><p><code><span class="label">static</span><a href="#isLeft"><span class="identifier">isLeft</span></a>&lt;<span class="type">L</span>, <span class="type">R</span>&gt; (<span style="white-space:nowrap">either:<a class="type" title="Either wraps one value of two possible types." href="../thx/Either.html">E