13 lines
798 B
HTML
13 lines
798 B
HTML
<h2 id="natural-transformation-examples-44">Natural Transformation Examples (4/4)</h2>
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<pre><code class="haskell small">mToList :: Maybe a -> [a]
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mToList Nothing = []
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mToList Just x = [x]</pre>
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</code>
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<p><code>toMaybe</code> is a natural transformation. It is also a morphism from <code>[]</code> to <code>Maybe</code> in the Category of \(\Hask\) endofunctors.</p>
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<img style="float:left;width:30%" src="categories/img/mp/nattrans-maybe-list.png" alt="natural transformation commutative diagram"/>
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<figure style="float:right;width:60%">
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<img style="width:40%" src="categories/img/mp/maybe-list-endofunctor-morphsm.png" alt="relation between [] and Maybe"/> <figcaption>There is <span class="red">no isomorphism</span>.<br/> Hint: <code>Bool</code> lists longer than 1. </figcaption>
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</figure>
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