<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="">Count me in, too.<div class=""><br class=""></div><div class="">Manuel</div><div class=""><div><br class=""><blockquote type="cite" class=""><div class="">Am 24.07.2018 um 21:01 schrieb Richard Eisenberg <<a href="mailto:rae@cs.brynmawr.edu" class="">rae@cs.brynmawr.edu</a>>:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html; charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Unsurprisingly, I'm in support. The lack of this ability has forced `singletons` to go through hoops to bind type variables in certain situations.<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Jul 24, 2018, at 12:25 PM, Simon Peyton Jones via ghc-steering-committee <<a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</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; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 12pt;" class="">I originally thought that it’d be confusing for ‘a’ to mean ‘Bool’; but that was before GADTs! Now that argument is much less strong, and I’m in favour of this proposal.<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 12pt;" class=""><br class="">Simon<o:p class=""></o:p></span></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><span style="font-size: 12pt;" class=""><o:p class=""> </o:p></span></div><div style="border-style: none none none solid; border-left-width: 1.5pt; border-left-color: blue; padding: 0cm 0cm 0cm 4pt;" class=""><div class=""><div style="border-style: solid none none; border-top-width: 1pt; border-top-color: rgb(225, 225, 225); padding: 3pt 0cm 0cm;" class=""><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><b class=""><span lang="EN-US" class="">From:</span></b><span lang="EN-US" class=""><span class="Apple-converted-space"> </span>ghc-steering-committee <<a href="mailto:ghc-steering-committee-bounces@haskell.org" class="">ghc-steering-committee-bounces@haskell.org</a>><span class="Apple-converted-space"> </span><b class="">On Behalf Of<span class="Apple-converted-space"> </span></b>Iavor Diatchki<br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>24 July 2018 17:23<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span><a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>[ghc-steering-committee] Discussion on "Allow ScopedTypeVariables to refer to types" (#128)<o:p class=""></o:p></span></div></div></div><div style="margin: 0cm 0cm 0.0001pt; font-size: 11pt; font-family: Calibri, sans-serif;" class=""><o:p class=""> </o:p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">Hello,<o:p class=""></o:p></p><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">let's get the discussion going on proposal #128.<o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">Summary: this proposal generalizes the behavior of type variables in patterns, specifically the variables that do not refer to an explicitly quantified type parameter. The idea is that such type variables simply introduce a name for their matching type, without placing any restriction on the type. For example, consider the following definition.<o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">f (x : [a]) (y : a) = and x<o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">This would be accepted and it would have type `[Bool] -> Bool -> Bool`. This proposal is about the meaning of the type signature on `x` which states that it must be a list of something, and `a` will be a name for the type of its elements. In this case, it happens that `a` is actually just an alias for `Bool`. <o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">I am strongly in favor of this proposal. As I mentioned on the github discussion, I thought that the feature already worked as in this proposal, and was quite surprised to find out that currently, GHC has restrictions on what `a` could be, and it also complains about "multiple definitions for `a`" in the above example).<o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">Thoughts?<o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;">-Iavor<o:p class=""></o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; font-size: 11pt; font-family: Calibri, sans-serif;"><o:p class=""> </o:p></p></div><div class=""><p class="MsoNormal" style="margin: 0cm 0cm 6pt; 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