<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><span></span></div><div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div></div><div><br></div><div><br>El 21 dic 2016, a las 02:36, Simon Peyton Jones via ghc-devs <<a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a>> escribió:<br></div><div><br></div><br><blockquote type="cite"><div class="WordSection1"><br>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:windowtext">I even wonder (whisper it) about taking it out altogether, when Edward says “</span>many of the original applications for arrows have been shown to be perfectly suited to being
handled by Applicatives<span style="font-family:"Calibri",sans-serif;color:windowtext">” (i.e. with no extensions except AppliciativeDo. But I have no data on whether anyone (at all) is using arrow notation these days, and if so how mission-critical it is
to them; and old packages like Yampa certainly use it. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:windowtext"><o:p> </o:p></span></p></div></blockquote><div><br></div><div>Unfortunately ApplicativeDo is for a very limited use-case, of the form:</div><div><br></div><div>do a0 <- x0</div><div> a1 <- x1 -- x1 cannot refer to a0</div><div> ...</div><div> pure ...</div><div> -- last line must be "pure", "pure $", "return" or "return $"</div><div><br></div><div>Additionally, Opaleye uses Arrow syntax pretty heavily iirc.</div><div><br></div><div>I haven't actually prototyped it, but I dream of an ApplicativeDo or ArrowDo which desugars do blocks with join in place of >>= , so any do-block which doesn't use any joins doesn't require the monad constraint...</div><div><br></div><div>Tom</div><div><br></div><style><!--
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