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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">Sounds like a good idea, could it be possible to use a typeclass instead of `NonEmpty (Set a)`?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif">I recall needing this a few times, but not over a NonEmpty.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span style="color:black">De:</span></b><span style="color:black"> Libraries <libraries-bounces@haskell.org> em nome de Reed Mullanix <reedmullanix@gmail.com><br>
<b>Enviado:</b> Sunday, December 6, 2020 6:20:02 AM<br>
<b>Para:</b> Haskell Libraries <libraries@haskell.org><br>
<b>Assunto:</b> containers: intersections for Set, along with Semigroup newtype</span>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Hey all,<o:p></o:p></p>
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<p class="MsoNormal">I've found myself reaching for the following function a couple of times now, so I figured it might make a good addition.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> intersections :: Ord a => NonEmpty (Set a) -> Set a<br>
intersections (s :| ss) = Foldable.foldl' intersection s ss<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">In a similar vein, we may as well add the following newtype + instance combo:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> newtype Intersection a = Intersection { getIntersection :: Set a }<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"> instance (Ord a) => Semigroup (Intersection a) where<br>
(Intersection a) <> (Intersection b) = Intersection $ intersection a b<br>
stimes = stimesIdempotent<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Would love to hear everyone's thoughts on this!<o:p></o:p></p>
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<p class="MsoNormal">Thanks<o:p></o:p></p>
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<p class="MsoNormal">Reed Mullanix<o:p></o:p></p>
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