Proposal: Add IsString and Monoid instances for Doc

Thomas Schilling nominolo at googlemail.com
Sun Oct 24 09:25:14 EDT 2010


Did you test how many packages this would break, i.e., how many
packages define their own instance for Monoid Doc?

On 24 October 2010 09:16, Bas van Dijk <v.dijk.bas at gmail.com> wrote:
> On Fri, Oct 8, 2010 at 9:52 AM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:
>> Hello,
>>
>> Since we're discussing a proposal for the pretty package I would like
>> to make another one:
>>
>> The proposal is to add the following to Text.PrettyPrint.HughesPJ:
>>
>> instance IsString Doc where
>>    fromString = text
>>
>> This allows users to use string literals as Doc values using the
>> OverloadedStrings language extension.
>>
>> I would also like to add:
>>
>> instance Monoid Doc where
>>    mempty  = empty
>>    mappend = (<>)
>>
>> If there's enough demand (because it's a lot of work) I can find out
>> if this change breaks anything by analyzing pretty's direct reverse
>> dependencies:
>>
>> http://bifunctor.homelinux.net/~roel/cgi-bin/hackage-scripts/revdeps/pretty-1.0.1.1#direct
>>
>> to see if some of them define an orphaned instance for IsString or Monoid.
>>
>> The patch that implements this is attached to the ticket:
>>
>> http://hackage.haskell.org/trac/ghc/ticket/4378
>>
>> Deadline: 2 weeks (Friday 22 October 2010)
>>
>> Regards,
>>
>> Bas
>>
>
> The deadline for this proposal has passed. There were no objections.
>
> I will move the ticket status to 'patch'.
>
> Thanks,
>
> Bas
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