Normally they shouldn't, although it's impossible to check in general. If you don't have orphan instances, you'll be alright.<div><br /></div><div>And if you do define conflicting instances, then yes, you can have very strange results. Conflicting Ord instances, for example, lead to Set containing the same element multiple times.<br /><br /><div>04.02.2016, 13:25, "Imants Cekusins" &lt;<a dir="ltr" href="mailto:imantc@gmail.com" x-apple-data-detectors="true" x-apple-data-detectors-type="link" x-apple-data-detectors-result="1">imantc@gmail.com</a>&gt;:</div><blockquote type="cite"><div><blockquote> Two modules defining different instances for the same class and type can't be used together.<br /></blockquote><p><br />it is possible to define conflicting instances for the same class/type<br />in modules that don't import one another - without strange results,<br />isn't it?<br /><br />or conflicting instances must not exist within the same app, including libs?<br />_______________________________________________<br />Haskell-Cafe mailing list<br /><a>Haskell-Cafe@haskell.org</a><br /><a href="http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe" data-vdir-href="http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe" data-orig-href="http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe" target="_blank">http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-caf…</a><br /></p></div></blockquote><div><br /></div><div><br /></div><div></div><div><br /></div></div>