<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div><div style="direction: inherit;">Monoid doesn't have fromInteger -like function. For example, we don't have FromString b => FromString (a -> b) instance.</div><div style="direction: inherit;"><br></div><div style="direction: inherit;">Unfortunately fromInteger is part of Num, so comparison with Monoid is unjust.</div><div style="direction: inherit;"><br></div>Sent from my iPhone</div><div><br>On 11 Nov 2018, at 23.44, Daniel Cartwright <<a href="mailto:chessai1996@gmail.com">chessai1996@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="auto">ANum seems to be just Data.Monoid.Ap. <div dir="auto">Also, I can see not wanting to worsen the error messages, though it is worth pointing out that we already have a Monoid instance with the same semantics, and a similar potential for confusing error messages.</div></div><br><div class="gmail_quote"><div dir="ltr">On Sun, Nov 11, 2018, 1:36 AM Dan Burton <<a href="mailto:danburton.email@gmail.com">danburton.email@gmail.com</a> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">-1, per the very confusing errors that would ensue.<br><br>If this behavior is desired, you can use a newtype wrapper. As it happens, this fits the pattern of <a href="http://hackage.haskell.org/package/ANum" target="_blank" rel="noreferrer">ANum</a>. (Any Applicative can be made an instance of Num in this way.)<div><br><div><div><div dir="ltr" class="m_6957556419282998197gmail_signature" data-smartmail="gmail_signature">-- Dan Burton</div></div><br><input name="virtru-metadata" type="hidden" value="{"email-policy":{"state":"closed","expirationUnit":"days","disableCopyPaste":false,"disablePrint":false,"disableForwarding":false,"enableNoauth":false,"expires":false,"isManaged":false},"attachments":{},"compose-id":"5","compose-window":{"secure":false}}"></div></div><br><div class="gmail_quote"><div dir="ltr">On Sun, Nov 11, 2018 at 12:28 AM Tom Murphy <<a href="mailto:amindfv@gmail.com" target="_blank" rel="noreferrer">amindfv@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On 11/11/18, Henning Thielemann <<a href="mailto:lemming@henning-thielemann.de" target="_blank" rel="noreferrer">lemming@henning-thielemann.de</a>> wrote:<br>
><br>
> On Sun, 11 Nov 2018, Henning Thielemann wrote:<br>
><br>
>> On Sat, 10 Nov 2018, Daniel Cartwright wrote:<br>
>><br>
>>> relevant reddit comment<br>
>>> thread:<a href="https://www.reddit.com/r/haskell/comments/9vtis5/the_universe_of_discourse_i_hate_the_environment/e9f1lea?utm_so" rel="noreferrer noreferrer" target="_blank">https://www.reddit.com/r/haskell/comments/9vtis5/the_universe_of_discourse_i_hate_the_environment/e9f1lea?utm_so</a><br>
>>> urce=reddit-android<br>
>><br>
>> <a href="https://wiki.haskell.org/index.php?title=Num_instance_for_functions&oldid=36632" rel="noreferrer noreferrer" target="_blank">https://wiki.haskell.org/index.php?title=Num_instance_for_functions&oldid=36632</a><br>
>><br>
>> In short: It would make 2(x+y) no longer a type error but equivalent to 2.<br>
>> We<br>
>> would lose a lot of type safety for little syntactic gain.<br>
><br>
> Btw. before adding more Wat instances please implement the GHC warning<br>
> about such instances:<br>
> <a href="https://ghc.haskell.org/trac/ghc/ticket/11796" rel="noreferrer noreferrer" target="_blank">https://ghc.haskell.org/trac/ghc/ticket/11796</a><br>
<br>
This is my feeling as well.<br>
<br>
Tom<br>
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