<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=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Mar 5, 2019, at 11:34 AM, Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com" class="">simonpj@microsoft.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; 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;"><div style="margin: 0cm 0cm 0.0001pt 36pt; font-size: 11pt; font-family: Calibri, sans-serif;" class="">I haven't thought through the consequences of this fully, but it does seem plausible.<o:p class=""></o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span class="">It says we must generalise over some ‘a’, but<span class="Apple-converted-space"> </span><i class="">which</i><span class="Apple-converted-space"> </span>‘a’? What type does (\@a (\x. x)) have? </span></div></div></div></blockquote><div><br class=""></div><div>My understanding of Eric's idea is that GHC would give (\x.x) the type (alpha -> alpha), as usual. Then (\ @a (\x.x)) gets the type forall a. alpha -> alpha. Later, we might solve for alpha or generalize over it, perhaps leading a type like forall b a. b -> b.</div><br class=""><blockquote type="cite" class=""><div class="WordSection1" style="page: WordSection1; caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; 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;"><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 11pt;" class="">But someone would need to write down a type system.</span></div></div></blockquote><div><br class=""></div><div>I agree here. I think we'd need more Medium Thought (not quite Hard Thought) before committing to this plan, but it still seems plausible.</div><div><br class=""></div><div>Richard</div></div></body></html>