<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">I worry that everyone has missed the final sentence of the proposal:<div class=""><br class=""></div><div class="">> This is already implemented, but it is easy enough to tweak the design.</div><div class=""><br class=""></div><div class="">This proposal is fully implemented in 8.4, and I believe it is, too, in 8.2. At the time the proposal was written, the new features had not been released, and it was hoped that the discussion would influence the design. But due to the fact that this was parked for so long, the implementation has since been released.</div><div class=""><br class=""></div><div class="">(Why the weird temporal ordering? Improvements around levity polymorphism that absolutely needed to get into 8.2 walked over this code. It was tangled and so I cleaned it up. It was only later that we recognized a proposal was in order.)</div><div class=""><br class=""></div><div class="">The big motivation for (A) is that it removes unboxed tuples (resp. sums) from being a special case. Now, we're uniform.</div><div class=""><br class=""></div><div class="">The big motivation for (B) is that it allows more (correct) programs to compile. The previous behavior was throwing out programs because GHC was worried that the author was being silly -- but that's precisely what warnings are good for.</div><div class=""><br class=""></div><div class="">Have I lost interest? Possibly. I've never cared all that deeply about this, other than that the code was quite hard to understand (and incorrect w.r.t. the manual) when I came across it. My lack of prodding on this issue was simply because the lack of an answer wasn't holding me up.</div><div class=""><br class=""></div><div class="">Richard<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Aug 17, 2018, at 2:37 AM, Eric Seidel <<a href="mailto:eric@seidel.io" class="">eric@seidel.io</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">I think the reason is more that it's a change that doesn't seem to be well-motivated, i.e. neither the proposal nor the discussion offer a compelling example where you would want an unboxed tuple to be matched lazily.</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">That being said, I overlooked the implicit-bang alternative when I first read the proposal. That seems quite reasonable. The default behavior remains what people seem to expect, but enables the explicit use of lazy patterns should you want them.</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><span style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; float: none; display: inline !important;" class="">On Thu, Aug 16, 2018, at 03:38, Simon Peyton Jones via ghc-steering-committee wrote:</span><br style="caret-color: rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><blockquote type="cite" style="font-family: Menlo-Regular; font-size: 11px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;" class="">I’m actually mildly in favour of the proposed design.<br class=""><br class="">The main reason for rejection is really<br class=""><br class="">* It’s a change<br class=""><br class="">Change is always a bit disruptive; and no one is arguing strongly that<span class="Apple-converted-space"> </span><br class="">they really really want this.<br class=""><br class="">So maybe we should just “park” it as OK in principle, but without<span class="Apple-converted-space"> </span><br class="">sufficient support to justify the (hard to quantify) changeover costs.<br class=""><br class="">Simon<br class=""><br class="">From: ghc-steering-committee <ghc-steering-committee-<br class=""><a href="mailto:bounces@haskell.org" class="">bounces@haskell.org</a>> On Behalf Of Vitaly Bragilevsky<br class="">Sent: 16 August 2018 01:37<br class="">To: <a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a><br class="">Subject: [ghc-steering-committee] Proposal: Lazy unboxed tuples / warn<span class="Apple-converted-space"> </span><br class="">on unbanged strict patterns (#35); Recommendation: Reject<br class=""><br class="">Hi,<br class=""><br class="">the lazy unboxed tuples proposal <br class="">(<a href="https://github.com/ghc-proposals/ghc-proposals/pull/35%3Chttps://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F35&data=02%7C01%7Csimonpj%40microsoft.com%7C983115e9eee64eb4b03c08d603107655%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636699766583676606&sdata=PXTsCrM4otm8ZCEFZvNfkydSBo6J77zh5qb9CVNmZX8%3D&reserved=0%3E" class="">https://github.com/ghc-proposals/ghc-proposals/pull/35<https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fghc-proposals%2Fghc-proposals%2Fpull%2F35&data=02%7C01%7Csimonpj%40microsoft.com%7C983115e9eee64eb4b03c08d603107655%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636699766583676606&sdata=PXTsCrM4otm8ZCEFZvNfkydSBo6J77zh5qb9CVNmZX8%3D&reserved=0></a>)<span class="Apple-converted-space"> </span><br class="">was under discussion for a long period of time (more than a year and a<span class="Apple-converted-space"> </span><br class="">half since submission).<br class=""><br class="">As a shepherd to this proposal I recommend rejection based on the following:<br class=""><br class="">* there is no clearly articulated motivation in favor of this proposal<span class="Apple-converted-space"> </span><br class="">despite complying with the Manual;<br class="">* implementing this would lead to hard-to-trace performance issues in<span class="Apple-converted-space"> </span><br class="">the users code (due to move from strictness in current GHC behaviour to<span class="Apple-converted-space"> </span><br class="">laziness);<br class="">* it looks like the change (B) of the proposal (warn an unbanged strict<span class="Apple-converted-space"> </span><br class="">patterns) meets no complains, so it is better to be resubmitted as a<span class="Apple-converted-space"> </span><br class="">separate proposal;<br class="">* if resubmitted separately the change (A) should elaborate on<span class="Apple-converted-space"> </span><br class="">desugaring to make potential performance drawbacks clear;<br class="">* it seems (maybe mistakenly) that the author has lost his interest in<span class="Apple-converted-space"> </span><br class="">this proposal.<br class=""><br class="">Although silence is undestood as agreement, I'd be glad to receive a<span class="Apple-converted-space"> </span><br class="">feedback on this recommendation.<br class=""><br class="">Regards,<br class="">Vitaly<br class="">_______________________________________________<br class="">ghc-steering-committee mailing list<br class=""><a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a><br class=""><a href="https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee" class="">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee</a><br class=""></blockquote><span style="caret-color: rgb(0, 0, 0); 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