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Diffstat (limited to 'docs/users_guide/ghci.rst')
| -rw-r--r-- | docs/users_guide/ghci.rst | 66 |
1 files changed, 33 insertions, 33 deletions
diff --git a/docs/users_guide/ghci.rst b/docs/users_guide/ghci.rst index 2e5d1ed9fa..21102c6846 100644 --- a/docs/users_guide/ghci.rst +++ b/docs/users_guide/ghci.rst @@ -2483,6 +2483,39 @@ commonly used commands. restriction (b), showing all instances that are in scope and mention ⟨name⟩ in their head. +.. ghci-cmd:: :instances; ⟨type⟩ + + Displays all the class instances available to the argument ⟨type⟩. + The command will match ⟨type⟩ with the first parameter of every + instance and then check that all constraints are satisfiable. + + When combined with :extension:`PartialTypeSignatures`, a user can insert + wildcards into a query and learn the constraints required of each + wildcard for ⟨type⟩ match with an instance. + + The output is a listing of all matching instances, simplified and + instantiated as much as possible. + + For example: + + .. code-block:: none + + > :instances Maybe (Maybe Int) + instance Eq (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’ + instance Ord (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’ + instance Show (Maybe (Maybe Int)) -- Defined in ‘GHC.Show’ + instance Read (Maybe (Maybe Int)) -- Defined in ‘GHC.Read’ + + > :set -XPartialTypeSignatures -fno-warn-partial-type-signatures + + > :instances Maybe _ + instance Eq _ => Eq (Maybe _) -- Defined in ‘GHC.Maybe’ + instance Semigroup _ => Monoid (Maybe _) -- Defined in ‘GHC.Base’ + instance Ord _ => Ord (Maybe _) -- Defined in ‘GHC.Maybe’ + instance Semigroup _ => Semigroup (Maybe _) -- Defined in ‘GHC.Base’ + instance Show _ => Show (Maybe _) -- Defined in ‘GHC.Show’ + instance Read _ => Read (Maybe _) -- Defined in ‘GHC.Read’ + .. ghci-cmd:: :issafe; [⟨module⟩] Displays Safe Haskell information about the given module (or the @@ -2571,39 +2604,6 @@ commonly used commands. The ``:loc-at`` command requires :ghci-cmd:`:set +c` to be set. -.. ghci-cmd:: :instances; ⟨type⟩ - - Displays all the class instances available to the argument ⟨type⟩. - The command will match ⟨type⟩ with the first parameter of every - instance and then check that all constraints are satisfiable. - - When combined with :extension:`PartialTypeSignatures`, a user can insert - wildcards into a query and learn the constraints required of each - wildcard for ⟨type⟩ match with an instance. - - The output is a listing of all matching instances, simplified and - instantiated as much as possible. - - For example: - - .. code-block:: none - - > :instances Maybe (Maybe Int) - instance Eq (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’ - instance Ord (Maybe (Maybe Int)) -- Defined in ‘GHC.Maybe’ - instance Show (Maybe (Maybe Int)) -- Defined in ‘GHC.Show’ - instance Read (Maybe (Maybe Int)) -- Defined in ‘GHC.Read’ - - > :set -XPartialTypeSignatures -fno-warn-partial-type-signatures - - > :instances Maybe _ - instance Eq _ => Eq (Maybe _) -- Defined in ‘GHC.Maybe’ - instance Semigroup _ => Monoid (Maybe _) -- Defined in ‘GHC.Base’ - instance Ord _ => Ord (Maybe _) -- Defined in ‘GHC.Maybe’ - instance Semigroup _ => Semigroup (Maybe _) -- Defined in ‘GHC.Base’ - instance Show _ => Show (Maybe _) -- Defined in ‘GHC.Show’ - instance Read _ => Read (Maybe _) -- Defined in ‘GHC.Read’ - .. ghci-cmd:: :main; ⟨arg1⟩ ... ⟨argn⟩ When a program is compiled and executed, it can use the ``getArgs`` |