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Re-order the definition of tryVia

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Taylor Fausak 2021-05-01 19:10:31 +00:00 committed by GitHub
parent a154c392cd
commit 2c5c9d69d6
1 changed files with 25 additions and 25 deletions
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50
src/lib/Witch/Utility.hs
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@ -125,6 +125,31 @@ tryInto
-> Either (TryCastException.TryCastException source target) target
tryInto = TryCast.tryCast
-- | This is similar to 'via' except that it works with 'TryCast.TryCast'
-- instances instead. This function is especially convenient because juggling
-- the types in the 'TryCastException.TryCastException' can be tedious.
--
-- > -- Avoid this:
-- > fmap (tryFrom @u) . tryInto @u
-- >
-- > -- Prefer this:
-- > tryVia @u
tryVia
:: forall u source target through
. ( Identity.Identity u ~ through
, TryCast.TryCast source through
, TryCast.TryCast through target
)
=> source
-> Either (TryCastException.TryCastException source target) target
tryVia s = case TryCast.tryCast s of
Left (TryCastException.TryCastException _ e) ->
Left $ TryCastException.TryCastException s e
Right u -> case TryCast.tryCast (u :: through) of
Left (TryCastException.TryCastException _ e) ->
Left $ TryCastException.TryCastException s e
Right t -> Right t
-- | This function can be used to implement 'TryCast.tryCast' with a function
-- that returns 'Maybe'. For example:
--
@ -163,31 +188,6 @@ eitherTryCast f s = case f s of
Left . TryCastException.TryCastException s . Just $ Exception.toException e
Right t -> Right t
-- | This is similar to 'via' except that it works with 'TryCast.TryCast'
-- instances instead. This function is especially convenient because juggling
-- the types in the 'TryCastException.TryCastException' can be tedious.
--
-- > -- Avoid this:
-- > fmap (tryFrom @u) . tryInto @u
-- >
-- > -- Prefer this:
-- > tryVia @u
tryVia
:: forall u source target through
. ( Identity.Identity u ~ through
, TryCast.TryCast source through
, TryCast.TryCast through target
)
=> source
-> Either (TryCastException.TryCastException source target) target
tryVia s = case TryCast.tryCast s of
Left (TryCastException.TryCastException _ e) ->
Left $ TryCastException.TryCastException s e
Right u -> case TryCast.tryCast (u :: through) of
Left (TryCastException.TryCastException _ e) ->
Left $ TryCastException.TryCastException s e
Right t -> Right t
-- | This function is like 'TryCast.tryCast' except that it will throw an
-- impure exception if the conversion fails.
--