composition 1.0.0.0 → 1.0.0.1

raw patch · 2 files changed

+26/−13 lines, 2 filesPVP ok

version bump matches the API change (PVP)

API changes (from Hackage documentation)

Files

• composition.cabal +2/−2
• src/Data/Composition.hs +24/−11

@@ -1,5 +1,5 @@ name:                composition
-version:             1.0.0.0
+version:             1.0.0.1
 synopsis:            Combinators for unorthodox function composition
 
 license:             BSD3
@@ -24,4 +24,4 @@ source-repository this
   type:     darcs
   location: http://patch-tag.com/r/DanBurton/composition
-  tag:      composition-1.0.0.0
+  tag:      composition-1.0.0.1

@@ -20,24 +20,37 @@ 
 -- Not exported. This is defined here to remove the dependency on base
 (.) :: (b -> c) -> (a -> b) -> a -> c
-(.) f g x = f (g x)
+(f . g) x = f (g x)
 
--- | This function is defined as
+-- | Compose two functions. @f .: g@ is similar to @f . g@
+-- except that @g@ will be fed /two/ arguments instead of one
+-- before handing its result to @f@.
 -- 
--- > (.:) f g x y = f (g x y)
+-- This function is defined as
 -- 
--- Example usage: @bind = join .: flip fmap@
--- Notice how two arguments will be given to @flip fmap@ before the result
--- is passed to @join@.
+-- > (f .: g) x y = f (g x y)
 -- 
--- This is equivalent to @bind v f = join (fmap v f)@
+-- Example usage:
+-- 
+-- > concatMap :: (a -> b) -> [a] -> [b]
+-- > concatMap = concat .: map
+-- 
+-- Notice how /two/ arguments
+-- (the function /and/ the list)
+-- will be given to @map@ before the result
+-- is passed to @concat@. This is equivalent to:
+-- 
+-- > concatMap f xs = concat (map f xs)
 (.:) :: (c -> d) -> (a -> b -> c) -> a -> b -> d
-(.:) f g x y = f (g x y)
+(f .: g) x y = f (g x y)
 
--- | Equivalent to '(.:)'
+-- | Equivalent to '.:'
 -- 
--- The pattern of appending asterisks is more extensible,
--- but uncommon in practice.
+-- The pattern of appending asterisks is
+-- more straightforward to extend to similar functions:
+-- (compose2 = .*, compose3 = .**, etc).
+-- However, @.:@ has been commonly adopted amongst Haskellers,
+-- and the need for compose3 and beyond is rare in practice.
 (.*) :: (c -> d) -> (a -> b -> c) -> a -> b -> d
 (.*) = (.) . (.)