Proposal: Add IsString and Monoid instances for Doc

Bas van Dijk v.dijk.bas at
Fri Oct 8 03:52:22 EDT 2010


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

to see if some of them define an orphaned instance for IsString or Monoid.

The patch that implements this is attached to the ticket:

Deadline: 2 weeks (Friday 22 October 2010)



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