diff options
| author | Oleg Grenrus <oleg.grenrus@iki.fi> | 2021-01-08 19:15:35 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-01-17 05:54:58 -0500 |
| commit | 907f1e4a8bb159c082c30d436f4555110e1055c2 (patch) | |
| tree | f84577ac95c9ce81ae8acc9000af27ba5f748444 /libraries/base/Data/Traversable.hs | |
| parent | 62cac31cd20708d7dd77131e0f822a3eed0d0661 (diff) | |
| download | haskell-907f1e4a8bb159c082c30d436f4555110e1055c2.tar.gz | |
Third pass on doctest corrections.
With `-K500K` rts option stack overflows are more deterministic
Diffstat (limited to 'libraries/base/Data/Traversable.hs')
| -rw-r--r-- | libraries/base/Data/Traversable.hs | 30 |
1 files changed, 22 insertions, 8 deletions
diff --git a/libraries/base/Data/Traversable.hs b/libraries/base/Data/Traversable.hs index 4d87cec29c..35f2c066b8 100644 --- a/libraries/base/Data/Traversable.hs +++ b/libraries/base/Data/Traversable.hs @@ -81,6 +81,9 @@ import qualified GHC.List as List ( foldr ) -- $setup -- >>> import Prelude +-- >>> import Data.Maybe (catMaybes, mapMaybe) +-- >>> import Data.Either (rights) +-- >>> import Data.Foldable (traverse_) -- XXX: Missing haddock feature. Links to anchors in other modules -- don't have a sensible way to name the link within the module itself. @@ -497,10 +500,17 @@ foldMapDefault = coerce (traverse :: (a -> Const m ()) -> t a -> Const m (t ())) -- over a list of file names produces an IO action that evaluates to a list -- of __@(fileName, lineCount)@__ pairs: -- --- >>> nameAndLineCount :: FilePath -> IO (FilePath, Int) --- >>> nameAndLineCount fn = ... --- >>> traverse nameAndLineCount ["/etc/passwd","/etc/hosts"] +-- @ +-- nameAndLineCount :: FilePath -> IO (FilePath, Int) +-- nameAndLineCount fn = ... +-- @ +-- +-- Then @traverse nameAndLineCount ["/etc/passwd","/etc/hosts"]@ +-- could return +-- +-- @ -- [("/etc/passwd",56),("/etc/hosts",32)] +-- @ -- -- The specialisation of 'traverse' to the case when __@f@__ is a monad is -- called 'mapM'. The two are otherwise generally identical: @@ -522,7 +532,7 @@ foldMapDefault = coerce (traverse :: (a -> Const m ()) -> t a -> Const m (t ())) -- replaced by each element of __@f a@__ in turn: -- -- >>> mapM (\n -> [0..n]) $ Just 2 --- [Just 0, Just 1, Just 2] +-- [Just 0,Just 1,Just 2] -- >>> mapM (\n -> [0..n]) [0..2] -- [[0,0,0],[0,0,1],[0,0,2],[0,1,0],[0,1,1],[0,1,2]] -- @@ -558,14 +568,18 @@ foldMapDefault = coerce (traverse :: (a -> Const m ()) -> t a -> Const m (t ())) -- #validation# -- A hypothetical application of the above is to validate a structure: -- --- >>> validate :: Int -> Either (String, Int) Int --- >>> validate i = if odd i then Left ("That's odd", i) else Right i +-- >>> :{ +-- validate :: Int -> Either (String, Int) Int +-- validate i = if odd i then Left ("That's odd", i) else Right i +-- :} +-- -- >>> traverse validate [2,4,6,8,10] -- Right [2,4,6,8,10] -- >>> traverse validate [2,4,6,8,9] -- Left ("That's odd",9) -- --- >>> -- Since 'Nothing' is an empty structure, none of its elements are odd. +-- Since 'Nothing' is an empty structure, none of its elements are odd. +-- -- >>> traverse validate Nothing -- Right Nothing -- >>> traverse validate (Just 42) @@ -585,7 +599,7 @@ foldMapDefault = coerce (traverse :: (a -> Const m ()) -> t a -> Const m (t ())) -- >>> traverse_ validate [2,4,6,8,9] -- Left ("That's odd",9) -- --- The @Foldable@ instance should be defined in a manner that avoids +-- The 'Foldable' instance should be defined in a manner that avoids -- construction of an unnecesary copy of the container. -- -- The @Foldable@ method 'mapM_' and its flipped version 'forM_' can be used |