Suggest default definition of Applicative
ghci> data A a = A a deriving (Show, Functor)
ghci> instance Monad A
<interactive>:3:10: error:
• No instance for (Applicative A)
arising from the superclasses of an instance declaration
• In the instance declaration for ‘Monad A’
could suggest defining it in terms of Monad
:
<interactive>:3:10: error:
• No instance for (Applicative A)
arising from the superclasses of an instance declaration
• In the instance declaration for ‘Monad A’
• Default implementation given a `Monad` instance:
instance Applicative A where
pure = return
(<*>) = Control.Monad.ap
Trac metadata
Trac field | Value |
---|---|
Version | 8.1 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | GHCi |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |