Ch6 - Clarify Action exercises #228
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milesfrain
changed the title
milesfrain
commented
Nov 3, 2020
milesfrain
commented
Nov 3, 2020
| @@ -113,17 +111,11 @@ newtype Self m | |||
| instance actionSelf :: Monoid m => Action m (Self m) where | |||
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Why is the Monoid constraint required here? It seems like this superclass relationship is already specified by the Action class and that it should be possible to write it like this instead:
instance actionSelf :: Action m (Self m) whereThere was a problem hiding this comment.
Answer:
it's required for the superclass relationship, it's not provided by the superclass relationship
milesfrain
commented
Nov 11, 2020
| mempty = Self mempty | ||
| -- These may also be written manualy | ||
| derive newtype instance showSelf :: Show m => Show (Self m) | ||
| derive newtype instance eqSelf :: Eq m => Eq (Self m) |
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Also fine to write without newtype wrapper:
derive instance eqSelf :: Eq m => Eq (Self m)
milesfrain
commented
Nov 11, 2020
| derive newtype instance showSelf :: Show m => Show (Self m) | ||
| derive newtype instance eqSelf :: Eq m => Eq (Self m) | ||
| derive newtype instance semigroupSelf :: Semigroup m => Semigroup (Self m) | ||
| derive newtype instance monoidSelf :: Monoid m => Monoid (Self m) | ||
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| instance repeatActionMultSelf :: Action (Self Multiply) Int where |
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This might not be the best instance name (doesn't follow the earlier convention of just squishing everything together), although this doesn't really matter.
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Fixes #200