diff options
| -rw-r--r-- | libraries/base/Data/Traversable.hs | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/libraries/base/Data/Traversable.hs b/libraries/base/Data/Traversable.hs index bdb2dc3db8..5454446bcb 100644 --- a/libraries/base/Data/Traversable.hs +++ b/libraries/base/Data/Traversable.hs @@ -115,13 +115,12 @@ import qualified GHC.List as List ( foldr ) -- 'Data.Functor.Compose.Compose' are from "Data.Functor.Identity" and -- "Data.Functor.Compose". -- --- A result of the naturality law is the intuitive generalised identity law --- for 'traverse' +-- A result of the naturality law is a `purity law` for 'traverse' -- -- @'traverse' 'pure' = 'pure'@ -- -- (The naturality law is implied by parametricity and thus so is the --- generalised identity law [reference not available, word of mouth].) +-- purity law [1, p15].) -- -- Instances are similar to 'Functor', e.g. given a data type -- @@ -146,6 +145,8 @@ import qualified GHC.List as List ( foldr ) -- equivalent to traversal with a constant applicative functor -- ('foldMapDefault'). -- +-- References: +-- [1] The Essence of the Iterator Pattern, Jeremy Gibbons and Bruno C. d. S. Oliveira class (Functor t, Foldable t) => Traversable t where {-# MINIMAL traverse | sequenceA #-} |