add GHC.HetMet.{hetmet_kappa,hetmet_kappa_app}

[ghc-base.git] / Data / Function.hs

diff --git a/Data/Function.hs b/Data/Function.hs
index 1de5eac..64ebfd0 100644 (file)
--- a/Data/Function.hs
+++ b/Data/Function.hs
@@ -14,6 +14,7 @@ module Data.Function
   ( -- * "Prelude" re-exports
     id, const, (.), flip, ($)
     -- * Other combinators
+  , fix
   , on
   ) where
 
@@ -21,6 +22,11 @@ import Prelude
 
 infixl 0 `on`
 
+-- | @'fix' f@ is the least fixed point of the function @f@,
+-- i.e. the least defined @x@ such that @f x = x@.
+fix :: (a -> a) -> a
+fix f = let x = f x in x
+
 -- | @(*) \`on\` f = \\x y -> f x * f y@.
 --
 -- Typical usage: @'Data.List.sortBy' ('compare' \`on\` 'fst')@.
@@ -74,4 +80,4 @@ infixl 0 `on`
 --   flip on (g . f)
 
 on :: (b -> b -> c) -> (a -> b) -> a -> a -> c
-(*) `on` f = \x y -> f x * f y
+(.*.) `on` f = \x y -> f x .*. f y