<div dir="ltr">Thanks, that really cleared up a few of the questions I had about Jake McArthurs' code as well. The link you provided was a good read and shed some more light on the situation.<div><br></div><div>The only bit I don't quite understand is why the following code implies an "or" relation in the type constraint of repr.</div>
<div><br></div><div><div>> data Stroke =</div><div>> Line Point Point (forall repr. (CirclePen repr, RectPen repr) => repr)</div><div>> | Arc Point Point (forall repr. (CirclePen repr) => repr)</div><div>
> | Spot Point (forall repr.</div><div>> (CirclePen repr, RectPen repr, ArbitraryPen repr) => repr)</div></div><div><br></div><div>To me this reads that repr should be both a CirclePen and a RectPen in order to satisfy the type constraint in the case of Line, but it seems that it is accepting a CirclePen or a RectPen (which is the desired behaviour, so I'm not complaining). </div>
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