Export Unicode and newline functionality from System.IO; update Haddock docs

[ghc-base.git] / GHC / Base.lhs

diff --git a/GHC/Base.lhs b/GHC/Base.lhs
index 2598583..3806d78 100644 (file)
--- a/GHC/Base.lhs
+++ b/GHC/Base.lhs
@@ -3,70 +3,68 @@
 The overall structure of the GHC Prelude is a bit tricky.
 
   a) We want to avoid "orphan modules", i.e. ones with instance
 The overall structure of the GHC Prelude is a bit tricky.
 
   a) We want to avoid "orphan modules", i.e. ones with instance

-       decls that don't belong either to a tycon or a class
-       defined in the same module
+        decls that don't belong either to a tycon or a class
+        defined in the same module

 
   b) We want to avoid giant modules
 
 So the rough structure is as follows, in (linearised) dependency order
 
 
 
   b) We want to avoid giant modules
 
 So the rough structure is as follows, in (linearised) dependency order
 
 

-GHC.Prim               Has no implementation.  It defines built-in things, and
-               by importing it you bring them into scope.
-               The source file is GHC.Prim.hi-boot, which is just
-               copied to make GHC.Prim.hi
+GHC.Prim                Has no implementation.  It defines built-in things, and
+                by importing it you bring them into scope.
+                The source file is GHC.Prim.hi-boot, which is just
+                copied to make GHC.Prim.hi

 
 

-               Classes: CCallable, CReturnable
+GHC.Base        Classes: Eq, Ord, Functor, Monad
+                Types:   list, (), Int, Bool, Ordering, Char, String

 
 

-GHC.Base       Classes: Eq, Ord, Functor, Monad
-               Types:   list, (), Int, Bool, Ordering, Char, String
+Data.Tuple      Types: tuples, plus instances for GHC.Base classes

 
 

-Data.Tup       Types: tuples, plus instances for GHC.Base classes
+GHC.Show        Class: Show, plus instances for GHC.Base/GHC.Tup types

 
 

-GHC.Show       Class: Show, plus instances for GHC.Base/GHC.Tup types
+GHC.Enum        Class: Enum,  plus instances for GHC.Base/GHC.Tup types

 
 

-GHC.Enum       Class: Enum,  plus instances for GHC.Base/GHC.Tup types
+Data.Maybe      Type: Maybe, plus instances for GHC.Base classes

 
 

-Data.Maybe     Type: Maybe, plus instances for GHC.Base classes
+GHC.List        List functions

 
 

-GHC.Num                Class: Num, plus instances for Int
-               Type:  Integer, plus instances for all classes so far (Eq, Ord, Num, Show)
+GHC.Num         Class: Num, plus instances for Int
+                Type:  Integer, plus instances for all classes so far (Eq, Ord, Num, Show)

 
 

-               Integer is needed here because it is mentioned in the signature
-               of 'fromInteger' in class Num
+                Integer is needed here because it is mentioned in the signature
+                of 'fromInteger' in class Num

 
 

-GHC.Real       Classes: Real, Integral, Fractional, RealFrac
-                        plus instances for Int, Integer
-               Types:  Ratio, Rational
-                       plus intances for classes so far
+GHC.Real        Classes: Real, Integral, Fractional, RealFrac
+                         plus instances for Int, Integer
+                Types:  Ratio, Rational
+                        plus intances for classes so far

 
 

-               Rational is needed here because it is mentioned in the signature
-               of 'toRational' in class Real
+                Rational is needed here because it is mentioned in the signature
+                of 'toRational' in class Real

 
 

-Ix             Classes: Ix, plus instances for Int, Bool, Char, Integer, Ordering, tuples
+GHC.ST  The ST monad, instances and a few helper functions

 
 

-GHC.Arr                Types: Array, MutableArray, MutableVar
+Ix              Classes: Ix, plus instances for Int, Bool, Char, Integer, Ordering, tuples

 
 

-               Does *not* contain any ByteArray stuff (see GHC.ByteArr)
-               Arrays are used by a function in GHC.Float
+GHC.Arr         Types: Array, MutableArray, MutableVar

 
 

-GHC.Float      Classes: Floating, RealFloat
-               Types:   Float, Double, plus instances of all classes so far
+                Arrays are used by a function in GHC.Float

 
 

-               This module contains everything to do with floating point.
-               It is a big module (900 lines)
-               With a bit of luck, many modules can be compiled without ever reading GHC.Float.hi
+GHC.Float       Classes: Floating, RealFloat
+                Types:   Float, Double, plus instances of all classes so far

 
 

-GHC.ByteArr    Types: ByteArray, MutableByteArray
-               
-               We want this one to be after GHC.Float, because it defines arrays
-               of unboxed floats.
+                This module contains everything to do with floating point.
+                It is a big module (900 lines)
+                With a bit of luck, many modules can be compiled without ever reading GHC.Float.hi

 
 
 Other Prelude modules are much easier with fewer complex dependencies.
 
 \begin{code}
 
 
 Other Prelude modules are much easier with fewer complex dependencies.
 
 \begin{code}

-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -XNoImplicitPrelude #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+{-# OPTIONS_HADDOCK hide #-}

 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.Base
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.Base

@@ -83,34 +81,48 @@ Other Prelude modules are much easier with fewer complex dependencies.
 
 #include "MachDeps.h"
 
 
 #include "MachDeps.h"
 

+-- #hide

 module GHC.Base
 module GHC.Base

-       (
-       module GHC.Base,
-       module GHC.Prim,        -- Re-export GHC.Prim and GHC.Err, to avoid lots
-       module GHC.Err          -- of people having to import it explicitly
+        (
+        module GHC.Base,
+        module GHC.Bool,
+        module GHC.Classes,
+        module GHC.Generics,
+        module GHC.Ordering,
+        module GHC.Types,
+        module GHC.Prim,        -- Re-export GHC.Prim and GHC.Err, to avoid lots
+        module GHC.Err          -- of people having to import it explicitly

   ) 
   ) 

-       where
+        where

 
 

+import GHC.Types
+import GHC.Bool
+import GHC.Classes
+import GHC.Generics
+import GHC.Ordering

 import GHC.Prim
 import {-# SOURCE #-} GHC.Err
 
 import GHC.Prim
 import {-# SOURCE #-} GHC.Err
 

+-- These two are not strictly speaking required by this module, but they are
+-- implicit dependencies whenever () or tuples are mentioned, so adding them
+-- as imports here helps to get the dependencies right in the new build system.
+import GHC.Tuple ()
+import GHC.Unit ()
+

 infixr 9  .
 infixr 9  .

-infixr 5  ++, :
-infix  4  ==, /=, <, <=, >=, >
-infixr 3  &&
-infixr 2  ||
+infixr 5  ++

 infixl 1  >>, >>=
 infixr 0  $
 
 infixl 1  >>, >>=
 infixr 0  $
 

-default ()             -- Double isn't available yet
+default ()              -- Double isn't available yet

 \end{code}
 
 
 %*********************************************************
 \end{code}
 
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{DEBUGGING STUFF}
 %*  (for use when compiling GHC.Base itself doesn't work)
 \subsection{DEBUGGING STUFF}
 %*  (for use when compiling GHC.Base itself doesn't work)

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 %*********************************************************
 
 \begin{code}

@@ -143,67 +155,65 @@ unpackCStringUtf8# a = error "urk"
 
 
 %*********************************************************
 
 
 %*********************************************************

-%*                                                     *
-\subsection{Standard classes @Eq@, @Ord@}
-%*                                                     *
+%*                                                      *
+\subsection{Monadic classes @Functor@, @Monad@ }
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 %*********************************************************
 
 \begin{code}

+{- | The 'Functor' class is used for types that can be mapped over.
+Instances of 'Functor' should satisfy the following laws:

 
 

--- | The 'Eq' class defines equality ('==') and inequality ('/=').
--- All the basic datatypes exported by the "Prelude" are instances of 'Eq',
--- and 'Eq' may be derived for any datatype whose constituents are also
--- instances of 'Eq'.
---
--- Minimal complete definition: either '==' or '/='.
---
-class  Eq a  where
-    (==), (/=)          :: a -> a -> Bool
-
-    x /= y              = not (x == y)
-    x == y              = not (x /= y)
-
-class  (Eq a) => Ord a  where
-    compare             :: a -> a -> Ordering
-    (<), (<=), (>), (>=) :: a -> a -> Bool
-    max, min            :: a -> a -> a
-
-    -- An instance of Ord should define either 'compare' or '<='.
-    -- Using 'compare' can be more efficient for complex types.
-
-    compare x y
-       | x == y    = EQ
-       | x <= y    = LT        -- NB: must be '<=' not '<' to validate the
-                               -- above claim about the minimal things that
-                               -- can be defined for an instance of Ord
-       | otherwise = GT
-
-    x <         y = case compare x y of { LT -> True;  _other -> False }
-    x <= y = case compare x y of { GT -> False; _other -> True }
-    x >         y = case compare x y of { GT -> True;  _other -> False }
-    x >= y = case compare x y of { LT -> False; _other -> True }
-
-       -- These two default methods use '<=' rather than 'compare'
-       -- because the latter is often more expensive
-    max x y = if x <= y then y else x
-    min x y = if x <= y then x else y
-\end{code}
+> fmap id  ==  id
+> fmap (f . g)  ==  fmap f . fmap g

 
 

-%*********************************************************
-%*                                                     *
-\subsection{Monadic classes @Functor@, @Monad@ }
-%*                                                     *
-%*********************************************************
+The instances of 'Functor' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
+defined in the "Prelude" satisfy these laws.
+-}

 
 

-\begin{code}

 class  Functor f  where
     fmap        :: (a -> b) -> f a -> f b
 
 class  Functor f  where
     fmap        :: (a -> b) -> f a -> f b
 

+{- | The 'Monad' class defines the basic operations over a /monad/,
+a concept from a branch of mathematics known as /category theory/.
+From the perspective of a Haskell programmer, however, it is best to
+think of a monad as an /abstract datatype/ of actions.
+Haskell's @do@ expressions provide a convenient syntax for writing
+monadic expressions.
+
+Minimal complete definition: '>>=' and 'return'.
+
+Instances of 'Monad' should satisfy the following laws:
+
+> return a >>= k  ==  k a
+> m >>= return  ==  m
+> m >>= (\x -> k x >>= h)  ==  (m >>= k) >>= h
+
+Instances of both 'Monad' and 'Functor' should additionally satisfy the law:
+
+> fmap f xs  ==  xs >>= return . f
+
+The instances of 'Monad' for lists, 'Data.Maybe.Maybe' and 'System.IO.IO'
+defined in the "Prelude" satisfy these laws.
+-}
+

 class  Monad m  where
 class  Monad m  where

-    (>>=)       :: m a -> (a -> m b) -> m b
-    (>>)        :: m a -> m b -> m b
+    -- | Sequentially compose two actions, passing any value produced
+    -- by the first as an argument to the second.
+    (>>=)       :: forall a b. m a -> (a -> m b) -> m b
+    -- | Sequentially compose two actions, discarding any value produced
+    -- by the first, like sequencing operators (such as the semicolon)
+    -- in imperative languages.
+    (>>)        :: forall a b. m a -> m b -> m b
+        -- Explicit for-alls so that we know what order to
+        -- give type arguments when desugaring
+
+    -- | Inject a value into the monadic type.

     return      :: a -> m a
     return      :: a -> m a

-    fail       :: String -> m a
+    -- | Fail with a message.  This operation is not part of the
+    -- mathematical definition of a monad, but is invoked on pattern-match
+    -- failure in a @do@ expression.
+    fail        :: String -> m a

 
     m >> k      = m >>= \_ -> k
     fail s      = error s
 
     m >> k      = m >>= \_ -> k
     fail s      = error s

@@ -211,15 +221,14 @@ class  Monad m  where
 
 
 %*********************************************************
 
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{The list type}
 \subsection{The list type}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 %*********************************************************
 
 \begin{code}

-data [] a = [] | a : [a]  -- do explicitly: deriving (Eq, Ord)
-                         -- to avoid weird names like con2tag_[]#
-
+-- do explicitly: deriving (Eq, Ord)
+-- to avoid weird names like con2tag_[]#

 
 instance (Eq a) => Eq [a] where
     {-# SPECIALISE instance Eq [Char] #-}
 
 instance (Eq a) => Eq [a] where
     {-# SPECIALISE instance Eq [Char] #-}

@@ -243,82 +252,112 @@ instance  Monad []  where
     m >>= k             = foldr ((++) . k) [] m
     m >> k              = foldr ((++) . (\ _ -> k)) [] m
     return x            = [x]
     m >>= k             = foldr ((++) . k) [] m
     m >> k              = foldr ((++) . (\ _ -> k)) [] m
     return x            = [x]

-    fail _             = []
+    fail _              = []

 \end{code}
 
 A few list functions that appear here because they are used here.
 The rest of the prelude list functions are in GHC.List.
 
 ----------------------------------------------
 \end{code}
 
 A few list functions that appear here because they are used here.
 The rest of the prelude list functions are in GHC.List.
 
 ----------------------------------------------

---     foldr/build/augment
+--      foldr/build/augment

 ----------------------------------------------
   
 \begin{code}
 ----------------------------------------------
   
 \begin{code}

+-- | 'foldr', applied to a binary operator, a starting value (typically
+-- the right-identity of the operator), and a list, reduces the list
+-- using the binary operator, from right to left:
+--
+-- > foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)
+

 foldr            :: (a -> b -> b) -> b -> [a] -> b
 -- foldr _ z []     =  z
 -- foldr f z (x:xs) =  f x (foldr f z xs)
 {-# INLINE [0] foldr #-}
 -- Inline only in the final stage, after the foldr/cons rule has had a chance
 foldr k z xs = go xs
 foldr            :: (a -> b -> b) -> b -> [a] -> b
 -- foldr _ z []     =  z
 -- foldr f z (x:xs) =  f x (foldr f z xs)
 {-# INLINE [0] foldr #-}
 -- Inline only in the final stage, after the foldr/cons rule has had a chance
 foldr k z xs = go xs

-            where
-              go []     = z
-              go (y:ys) = y `k` go ys
+             where
+               go []     = z
+               go (y:ys) = y `k` go ys
+
+-- | A list producer that can be fused with 'foldr'.
+-- This function is merely
+--
+-- >    build g = g (:) []
+--
+-- but GHC's simplifier will transform an expression of the form
+-- @'foldr' k z ('build' g)@, which may arise after inlining, to @g k z@,
+-- which avoids producing an intermediate list.

 
 

-build  :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]
+build   :: forall a. (forall b. (a -> b -> b) -> b -> b) -> [a]

 {-# INLINE [1] build #-}
 {-# INLINE [1] build #-}

-       -- The INLINE is important, even though build is tiny,
-       -- because it prevents [] getting inlined in the version that
-       -- appears in the interface file.  If [] *is* inlined, it
-       -- won't match with [] appearing in rules in an importing module.
-       --
-       -- The "1" says to inline in phase 1
+        -- The INLINE is important, even though build is tiny,
+        -- because it prevents [] getting inlined in the version that
+        -- appears in the interface file.  If [] *is* inlined, it
+        -- won't match with [] appearing in rules in an importing module.
+        --
+        -- The "1" says to inline in phase 1

 
 build g = g (:) []
 
 
 build g = g (:) []
 

+-- | A list producer that can be fused with 'foldr'.
+-- This function is merely
+--
+-- >    augment g xs = g (:) xs
+--
+-- but GHC's simplifier will transform an expression of the form
+-- @'foldr' k z ('augment' g xs)@, which may arise after inlining, to
+-- @g k ('foldr' k z xs)@, which avoids producing an intermediate list.
+

 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
 {-# INLINE [1] augment #-}
 augment g xs = g (:) xs
 
 {-# RULES
 augment :: forall a. (forall b. (a->b->b) -> b -> b) -> [a] -> [a]
 {-# INLINE [1] augment #-}
 augment g xs = g (:) xs
 
 {-# RULES

-"fold/build"   forall k z (g::forall b. (a->b->b) -> b -> b) . 
-               foldr k z (build g) = g k z
+"fold/build"    forall k z (g::forall b. (a->b->b) -> b -> b) . 
+                foldr k z (build g) = g k z

 
 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) . 
 
 "foldr/augment" forall k z xs (g::forall b. (a->b->b) -> b -> b) . 

-               foldr k z (augment g xs) = g k (foldr k z xs)
+                foldr k z (augment g xs) = g k (foldr k z xs)

 
 

-"foldr/id"                       foldr (:) [] = \x->x
-"foldr/app"            [1] forall xs ys. foldr (:) ys xs = xs ++ ys
-       -- Only activate this from phase 1, because that's
-       -- when we disable the rule that expands (++) into foldr
+"foldr/id"                        foldr (:) [] = \x  -> x
+"foldr/app"     [1] forall ys. foldr (:) ys = \xs -> xs ++ ys
+        -- Only activate this from phase 1, because that's
+        -- when we disable the rule that expands (++) into foldr

 
 -- The foldr/cons rule looks nice, but it can give disastrously
 -- bloated code when commpiling
 
 -- The foldr/cons rule looks nice, but it can give disastrously
 -- bloated code when commpiling

---     array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]
+--      array (a,b) [(1,2), (2,2), (3,2), ...very long list... ]

 -- i.e. when there are very very long literal lists
 -- So I've disabled it for now. We could have special cases
 -- for short lists, I suppose.
 -- i.e. when there are very very long literal lists
 -- So I've disabled it for now. We could have special cases
 -- for short lists, I suppose.

--- "foldr/cons"        forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)
+-- "foldr/cons" forall k z x xs. foldr k z (x:xs) = k x (foldr k z xs)

 
 

-"foldr/single" forall k z x. foldr k z [x] = k x z
-"foldr/nil"    forall k z.   foldr k z []  = z 
+"foldr/single"  forall k z x. foldr k z [x] = k x z
+"foldr/nil"     forall k z.   foldr k z []  = z 

 
 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)
 
 "augment/build" forall (g::forall b. (a->b->b) -> b -> b)

-                      (h::forall b. (a->b->b) -> b -> b) .
-                      augment g (build h) = build (\c n -> g c (h c n))
+                       (h::forall b. (a->b->b) -> b -> b) .
+                       augment g (build h) = build (\c n -> g c (h c n))

 "augment/nil"   forall (g::forall b. (a->b->b) -> b -> b) .
 "augment/nil"   forall (g::forall b. (a->b->b) -> b -> b) .

-                       augment g [] = build g
+                        augment g [] = build g

  #-}
 
 -- This rule is true, but not (I think) useful:
  #-}
 
 -- This rule is true, but not (I think) useful:

---     augment g (augment h t) = augment (\cn -> g c (h c n)) t
+--      augment g (augment h t) = augment (\cn -> g c (h c n)) t

 \end{code}
 
 
 ----------------------------------------------
 \end{code}
 
 
 ----------------------------------------------

---             map     
+--              map     

 ----------------------------------------------
 
 \begin{code}
 ----------------------------------------------
 
 \begin{code}

+-- | 'map' @f xs@ is the list obtained by applying @f@ to each element
+-- of @xs@, i.e.,
+--
+-- > map f [x1, x2, ..., xn] == [f x1, f x2, ..., f xn]
+-- > map f [x1, x2, ...] == [f x1, f x2, ...]
+

 map :: (a -> b) -> [a] -> [b]
 map _ []     = []
 map f (x:xs) = f x : map f xs
 map :: (a -> b) -> [a] -> [b]
 map _ []     = []
 map f (x:xs) = f x : map f xs

@@ -347,120 +386,109 @@ mapFB c f x ys = c (f x) ys
 -- e.g. append, filter, iterate, repeat, etc.
 
 {-# RULES
 -- e.g. append, filter, iterate, repeat, etc.
 
 {-# RULES

-"map"      [~1] forall f xs.   map f xs                = build (\c n -> foldr (mapFB c f) n xs)
-"mapList"   [1]  forall f.     foldr (mapFB (:) f) []  = map f
-"mapFB"            forall c f g.       mapFB (mapFB c f) g     = mapFB c (f.g) 
+"map"       [~1] forall f xs.   map f xs                = build (\c n -> foldr (mapFB c f) n xs)
+"mapList"   [1]  forall f.      foldr (mapFB (:) f) []  = map f
+"mapFB"     forall c f g.       mapFB (mapFB c f) g     = mapFB c (f.g) 

   #-}
 \end{code}
 
 
 ----------------------------------------------
   #-}
 \end{code}
 
 
 ----------------------------------------------

---             append  
+--              append  

 ----------------------------------------------
 \begin{code}
 ----------------------------------------------
 \begin{code}

+-- | Append two lists, i.e.,
+--
+-- > [x1, ..., xm] ++ [y1, ..., yn] == [x1, ..., xm, y1, ..., yn]
+-- > [x1, ..., xm] ++ [y1, ...] == [x1, ..., xm, y1, ...]
+--
+-- If the first list is not finite, the result is the first list.
+

 (++) :: [a] -> [a] -> [a]
 (++) []     ys = ys
 (++) (x:xs) ys = x : xs ++ ys
 
 {-# RULES
 (++) :: [a] -> [a] -> [a]
 (++) []     ys = ys
 (++) (x:xs) ys = x : xs ++ ys
 
 {-# RULES

-"++"   [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys
+"++"    [~1] forall xs ys. xs ++ ys = augment (\c n -> foldr c n xs) ys

   #-}
 
 \end{code}
 
 
 %*********************************************************
   #-}
 
 \end{code}
 
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{Type @Bool@}
 \subsection{Type @Bool@}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 -- |The 'Bool' type is an enumeration.  It is defined with 'False'
 %*********************************************************
 
 \begin{code}
 -- |The 'Bool' type is an enumeration.  It is defined with 'False'

--- first so that the corresponding 'Enum' instance will give @'fromEnum'
--- False@ the value zero, and @'fromEnum' True@ the value 1.
-data  Bool  =  False | True  deriving (Eq, Ord)
-       -- Read in GHC.Read, Show in GHC.Show
-
--- Boolean functions
-
--- | Boolean \"and\"
-(&&)                   :: Bool -> Bool -> Bool
-True  && x             =  x
-False && _             =  False
-
--- | Boolean \"or\"
-(||)                   :: Bool -> Bool -> Bool
-True  || _             =  True
-False || x             =  x
-
--- | Boolean \"not\"
-not                    :: Bool -> Bool
-not True               =  False
-not False              =  True
-
--- |'otherwise' is defined as the value 'True'; it helps to make
+-- first so that the corresponding 'Prelude.Enum' instance will give
+-- 'Prelude.fromEnum' 'False' the value zero, and
+-- 'Prelude.fromEnum' 'True' the value 1.
+-- The actual definition is in the ghc-prim package.
+
+-- XXX These don't work:
+-- deriving instance Eq Bool
+-- deriving instance Ord Bool
+-- <wired into compiler>:
+--     Illegal binding of built-in syntax: con2tag_Bool#
+
+instance Eq Bool where
+    True  == True  = True
+    False == False = True
+    _     == _     = False
+
+instance Ord Bool where
+    compare False True  = LT
+    compare True  False = GT
+    compare _     _     = EQ
+
+-- Read is in GHC.Read, Show in GHC.Show
+
+-- |'otherwise' is defined as the value 'True'.  It helps to make

 -- guards more readable.  eg.
 --
 -- guards more readable.  eg.
 --

--- >  f x | x \< 0     = ...
+-- >  f x | x < 0     = ...

 -- >      | otherwise = ...
 -- >      | otherwise = ...

-otherwise              :: Bool
-otherwise              =  True
+otherwise               :: Bool
+otherwise               =  True

 \end{code}
 
 \end{code}
 

-
-%*********************************************************
-%*                                                     *
-\subsection{The @()@ type}
-%*                                                     *
-%*********************************************************
-
-The Unit type is here because virtually any program needs it (whereas
-some programs may get away without consulting GHC.Tup).  Furthermore,
-the renamer currently *always* asks for () to be in scope, so that
-ccalls can use () as their default type; so when compiling GHC.Base we
-need ().  (We could arrange suck in () only if -fglasgow-exts, but putting
-it here seems more direct.)
-
-\begin{code}
--- | The unit datatype @()@ has one non-undefined member, the nullary
--- constructor @()@.
-data () = ()
-
-instance Eq () where
-    () == () = True
-    () /= () = False
-
-instance Ord () where
-    () <= () = True
-    () <  () = False
-    () >= () = True
-    () >  () = False
-    max () () = ()
-    min () () = ()
-    compare () () = EQ
-\end{code}
-
-

 %*********************************************************
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{Type @Ordering@}
 \subsection{Type @Ordering@}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 -- | Represents an ordering relationship between two values: less
 -- than, equal to, or greater than.  An 'Ordering' is returned by
 -- 'compare'.
 %*********************************************************
 
 \begin{code}
 -- | Represents an ordering relationship between two values: less
 -- than, equal to, or greater than.  An 'Ordering' is returned by
 -- 'compare'.

-data Ordering = LT | EQ | GT deriving (Eq, Ord)
-       -- Read in GHC.Read, Show in GHC.Show
+-- XXX These don't work:
+-- deriving instance Eq Ordering
+-- deriving instance Ord Ordering
+-- Illegal binding of built-in syntax: con2tag_Ordering#
+instance Eq Ordering where
+    EQ == EQ = True
+    LT == LT = True
+    GT == GT = True
+    _  == _  = False
+        -- Read in GHC.Read, Show in GHC.Show
+
+instance Ord Ordering where
+    LT <= _  = True
+    _  <= LT = False
+    EQ <= _  = True
+    _  <= EQ = False
+    GT <= GT = True

 \end{code}
 
 
 %*********************************************************
 \end{code}
 
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{Type @Char@ and @String@}
 \subsection{Type @Char@ and @String@}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 %*********************************************************
 
 \begin{code}

@@ -470,13 +498,17 @@ data Ordering = LT | EQ | GT deriving (Eq, Ord)
 type String = [Char]
 
 {-| The character type 'Char' is an enumeration whose values represent
 type String = [Char]
 
 {-| The character type 'Char' is an enumeration whose values represent

-Unicode characters.  A character literal in Haskell has type 'Char'.
-
-To convert a 'Char' to or from an 'Int', use 'Prelude.toEnum' and
-'Prelude.fromEnum' from the 'Enum' class respectively (equivalently
-'ord' and 'chr' also do the trick).
+Unicode (or equivalently ISO\/IEC 10646) characters
+(see <http://www.unicode.org/> for details).
+This set extends the ISO 8859-1 (Latin-1) character set
+(the first 256 charachers), which is itself an extension of the ASCII
+character set (the first 128 characters).
+A character literal in Haskell has type 'Char'.
+
+To convert a 'Char' to or from the corresponding 'Int' value defined
+by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
+'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').

 -}
 -}

-data Char = C# Char#

 
 -- We don't use deriving for Eq and Ord, because for Ord the derived
 -- instance defines only compare, which takes two primops.  Then
 
 -- We don't use deriving for Eq and Ord, because for Ord the derived
 -- instance defines only compare, which takes two primops.  Then

@@ -501,6 +533,7 @@ instance Ord Char where
 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
   #-}
 
 "x# `ltChar#` x#" forall x#. x# `ltChar#` x# = False
   #-}
 

+-- | The 'Prelude.toEnum' method restricted to the type 'Data.Char.Char'.

 chr :: Int -> Char
 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
             | otherwise                                  = error "Prelude.chr: bad argument"
 chr :: Int -> Char
 chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
             | otherwise                                  = error "Prelude.chr: bad argument"

@@ -508,6 +541,7 @@ chr (I# i#) | int2Word# i# `leWord#` int2Word# 0x10FFFF# = C# (chr# i#)
 unsafeChr :: Int -> Char
 unsafeChr (I# i#) = C# (chr# i#)
 
 unsafeChr :: Int -> Char
 unsafeChr (I# i#) = C# (chr# i#)
 

+-- | The 'Prelude.fromEnum' method restricted to the type 'Data.Char.Char'.

 ord :: Char -> Int
 ord (C# c#) = I# (ord# c#)
 \end{code}
 ord :: Char -> Int
 ord (C# c#) = I# (ord# c#)
 \end{code}

@@ -516,27 +550,23 @@ String equality is used when desugaring pattern-matches against strings.
 
 \begin{code}
 eqString :: String -> String -> Bool
 
 \begin{code}
 eqString :: String -> String -> Bool

-eqString []       []      = True
+eqString []       []       = True

 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2
 eqString (c1:cs1) (c2:cs2) = c1 == c2 && cs1 `eqString` cs2

-eqString cs1      cs2     = False
+eqString _        _        = False

 
 {-# RULES "eqString" (==) = eqString #-}
 
 {-# RULES "eqString" (==) = eqString #-}

+-- eqString also has a BuiltInRule in PrelRules.lhs:
+--      eqString (unpackCString# (Lit s1)) (unpackCString# (Lit s2) = s1==s2

 \end{code}
 
 
 %*********************************************************
 \end{code}
 
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{Type @Int@}
 \subsection{Type @Int@}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 %*********************************************************
 
 \begin{code}

-data Int = I# Int#
--- ^A fixed-precision integer type with at least the range @[-2^29
--- .. 2^29-1]@.  The exact range for a given implementation can be
--- determined by using 'minBound' and 'maxBound' from the 'Bounded'
--- class.
-

 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
 zeroInt = I# 0#
 oneInt  = I# 1#
 zeroInt, oneInt, twoInt, maxInt, minInt :: Int
 zeroInt = I# 0#
 oneInt  = I# 1#

@@ -577,100 +607,108 @@ compareInt# x# y#
 
 
 %*********************************************************
 
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{The function type}
 \subsection{The function type}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 %*********************************************************
 
 \begin{code}

--- identity function
-id                     :: a -> a
-id x                   =  x
+-- | Identity function.
+id                      :: a -> a
+id x                    =  x

 
 

--- lazy function; this is just the same as id, but its unfolding
--- and strictness are over-ridden by the definition in MkId.lhs
--- That way, it does not get inlined, and the strictness analyser
--- sees it as lazy.  Then the worker/wrapper phase inlines it.
--- Result: happiness
+-- | The call '(lazy e)' means the same as 'e', but 'lazy' has a 
+-- magical strictness property: it is lazy in its first argument, 
+-- even though its semantics is strict.

 lazy :: a -> a
 lazy x = x
 lazy :: a -> a
 lazy x = x

+-- Implementation note: its strictness and unfolding are over-ridden
+-- by the definition in MkId.lhs; in both cases to nothing at all.
+-- That way, 'lazy' does not get inlined, and the strictness analyser
+-- sees it as lazy.  Then the worker/wrapper phase inlines it.
+-- Result: happiness

 
 

--- Assertion function. This simply ignores its boolean argument.
--- The compiler may rewrite it to (assertError line)
---     SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
---     but from Template Haskell onwards it's simply
---     defined here in Base.lhs
-assert :: Bool -> a -> a
-assert pred r = r
- 
--- constant function
-const                  :: a -> b -> a
-const x _              =  x
-
--- function composition
-{-# INLINE (.) #-}
-(.)      :: (b -> c) -> (a -> b) -> a -> c
-(.) f g        x = f (g x)

 
 

--- flip f  takes its (first) two arguments in the reverse order of f.
-flip                   :: (a -> b -> c) -> b -> a -> c
-flip f x y             =  f y x
+-- | The call '(inline f)' reduces to 'f', but 'inline' has a BuiltInRule
+-- that tries to inline 'f' (if it has an unfolding) unconditionally
+-- The 'NOINLINE' pragma arranges that inline only gets inlined (and
+-- hence eliminated) late in compilation, after the rule has had
+-- a god chance to fire.
+inline :: a -> a
+{-# NOINLINE[0] inline #-}
+inline x = x

 
 

--- right-associating infix application operator (useful in continuation-
--- passing style)
-{-# INLINE ($) #-}
-($)                    :: (a -> b) -> a -> b
-f $ x                  =  f x
+-- Assertion function.  This simply ignores its boolean argument.
+-- The compiler may rewrite it to @('assertError' line)@.

 
 

--- until p f  yields the result of applying f until p holds.
-until                  :: (a -> Bool) -> (a -> a) -> a -> a
-until p f x | p x      =  x
-           | otherwise =  until p f (f x)
+-- | If the first argument evaluates to 'True', then the result is the
+-- second argument.  Otherwise an 'AssertionFailed' exception is raised,
+-- containing a 'String' with the source file and line number of the
+-- call to 'assert'.
+--
+-- Assertions can normally be turned on or off with a compiler flag
+-- (for GHC, assertions are normally on unless optimisation is turned on 
+-- with @-O@ or the @-fignore-asserts@
+-- option is given).  When assertions are turned off, the first
+-- argument to 'assert' is ignored, and the second argument is
+-- returned as the result.
+
+--      SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
+--      but from Template Haskell onwards it's simply
+--      defined here in Base.lhs
+assert :: Bool -> a -> a
+assert _pred r = r

 
 

--- asTypeOf is a type-restricted version of const.  It is usually used
--- as an infix operator, and its typing forces its first argument
--- (which is usually overloaded) to have the same type as the second.
-asTypeOf               :: a -> a -> a
-asTypeOf               =  const
-\end{code}
+breakpoint :: a -> a
+breakpoint r = r

 
 

-%*********************************************************
-%*                                                     *
-\subsection{CCallable instances}
-%*                                                     *
-%*********************************************************
+breakpointCond :: Bool -> a -> a
+breakpointCond _ r = r

 
 

-Defined here to avoid orphans
+data Opaque = forall a. O a

 
 

-\begin{code}
-instance CCallable Char
-instance CReturnable Char
+-- | Constant function.
+const                   :: a -> b -> a
+const x _               =  x

 
 

-instance CCallable   Int
-instance CReturnable Int
+-- | Function composition.
+{-# INLINE (.) #-}
+(.)       :: (b -> c) -> (a -> b) -> a -> c
+(.) f g x = f (g x)

 
 

-instance CReturnable () -- Why, exactly?
-\end{code}
+-- | @'flip' f@ takes its (first) two arguments in the reverse order of @f@.
+flip                    :: (a -> b -> c) -> b -> a -> c
+flip f x y              =  f y x

 
 

+-- | Application operator.  This operator is redundant, since ordinary
+-- application @(f x)@ means the same as @(f '$' x)@. However, '$' has
+-- low, right-associative binding precedence, so it sometimes allows
+-- parentheses to be omitted; for example:
+--
+-- >     f $ g $ h x  =  f (g (h x))
+--
+-- It is also useful in higher-order situations, such as @'map' ('$' 0) xs@,
+-- or @'Data.List.zipWith' ('$') fs xs@.
+{-# INLINE ($) #-}
+($)                     :: (a -> b) -> a -> b
+f $ x                   =  f x

 
 

-%*********************************************************
-%*                                                     *
-\subsection{Generics}
-%*                                                     *
-%*********************************************************
+-- | @'until' p f@ yields the result of applying @f@ until @p@ holds.
+until                   :: (a -> Bool) -> (a -> a) -> a -> a
+until p f x | p x       =  x
+            | otherwise =  until p f (f x)

 
 

-\begin{code}
-data Unit = Unit
-#ifndef __HADDOCK__
-data (:+:) a b = Inl a | Inr b
-data (:*:) a b = a :*: b
-#endif
+-- | 'asTypeOf' is a type-restricted version of 'const'.  It is usually
+-- used as an infix operator, and its typing forces its first argument
+-- (which is usually overloaded) to have the same type as the second.
+asTypeOf                :: a -> a -> a
+asTypeOf                =  const

 \end{code}
 
 %*********************************************************
 \end{code}
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{@getTag@}
 \subsection{@getTag@}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 Returns the 'tag' of a constructor application; this function is used
 %*********************************************************
 
 Returns the 'tag' of a constructor application; this function is used

@@ -692,17 +730,17 @@ getTag x = x `seq` dataToTag# x
 \end{code}
 
 %*********************************************************
 \end{code}
 
 %*********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{Numeric primops}
 \subsection{Numeric primops}

-%*                                                     *
+%*                                                      *

 %*********************************************************
 
 \begin{code}
 divInt# :: Int# -> Int# -> Int#
 x# `divInt#` y#
 %*********************************************************
 
 \begin{code}
 divInt# :: Int# -> Int# -> Int#
 x# `divInt#` y#

-       -- Be careful NOT to overflow if we do any additional arithmetic
-       -- on the arguments...  the following  previous version of this
-       -- code has problems with overflow:
+        -- Be careful NOT to overflow if we do any additional arithmetic
+        -- on the arguments...  the following  previous version of this
+        -- code has problems with overflow:

 --    | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
 --    | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
     | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#
 --    | (x# ># 0#) && (y# <# 0#) = ((x# -# y#) -# 1#) `quotInt#` y#
 --    | (x# <# 0#) && (y# ># 0#) = ((x# -# y#) +# 1#) `quotInt#` y#
     | (x# ># 0#) && (y# <# 0#) = ((x# -# 1#) `quotInt#` y#) -# 1#

@@ -715,7 +753,7 @@ x# `modInt#` y#
       (x# <# 0#) && (y# ># 0#)    = if r# /=# 0# then r# +# y# else 0#
     | otherwise                   = r#
     where
       (x# <# 0#) && (y# ># 0#)    = if r# /=# 0# then r# +# y# else 0#
     | otherwise                   = r#
     where

-    r# = x# `remInt#` y#
+    !r# = x# `remInt#` y#

 \end{code}
 
 Definitions of the boxed PrimOps; these will be
 \end{code}
 
 Definitions of the boxed PrimOps; these will be

@@ -735,7 +773,7 @@ used in the case of partial applications, etc.
 {-# INLINE remInt #-}
 {-# INLINE negateInt #-}
 
 {-# INLINE remInt #-}
 {-# INLINE negateInt #-}
 

-plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> Int -> Int
+plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt :: Int -> Int -> Int

 (I# x) `plusInt`  (I# y) = I# (x +# y)
 (I# x) `minusInt` (I# y) = I# (x -# y)
 (I# x) `timesInt` (I# y) = I# (x *# y)
 (I# x) `plusInt`  (I# y) = I# (x +# y)
 (I# x) `minusInt` (I# y) = I# (x -# y)
 (I# x) `timesInt` (I# y) = I# (x *# y)

@@ -755,17 +793,6 @@ plusInt, minusInt, timesInt, quotInt, remInt, divInt, modInt, gcdInt :: Int -> I
 "1# *# x#" forall x#. 1# *# x# = x#
   #-}
 
 "1# *# x#" forall x#. 1# *# x# = x#
   #-}
 

-gcdInt (I# a) (I# b) = g a b
-   where g 0# 0# = error "GHC.Base.gcdInt: gcd 0 0 is undefined"
-         g 0# _  = I# absB
-         g _  0# = I# absA
-         g _  _  = I# (gcdInt# absA absB)
-
-         absInt x = if x <# 0# then negateInt# x else x
-
-         absA     = absInt a
-         absB     = absInt b
-

 negateInt :: Int -> Int
 negateInt (I# x) = I# (negateInt# x)
 
 negateInt :: Int -> Int
 negateInt (I# x) = I# (negateInt# x)
 

@@ -802,14 +829,26 @@ gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
 "plusDouble x 0.0"   forall x#. (+##) x#    0.0## = x#
 "plusDouble 0.0 x"   forall x#. (+##) 0.0## x#    = x#
 "minusDouble x 0.0"  forall x#. (-##) x#    0.0## = x#
 "plusDouble x 0.0"   forall x#. (+##) x#    0.0## = x#
 "plusDouble 0.0 x"   forall x#. (+##) 0.0## x#    = x#
 "minusDouble x 0.0"  forall x#. (-##) x#    0.0## = x#

-"minusDouble x x"    forall x#. (-##) x#    x#    = 0.0##
-"timesDouble x 0.0"  forall x#. (*##) x#    0.0## = 0.0##
-"timesDouble 0.0 x"  forall x#. (*##) 0.0## x#    = 0.0##

 "timesDouble x 1.0"  forall x#. (*##) x#    1.0## = x#
 "timesDouble 1.0 x"  forall x#. (*##) 1.0## x#    = x#
 "divideDouble x 1.0" forall x#. (/##) x#    1.0## = x#
   #-}
 
 "timesDouble x 1.0"  forall x#. (*##) x#    1.0## = x#
 "timesDouble 1.0 x"  forall x#. (*##) 1.0## x#    = x#
 "divideDouble x 1.0" forall x#. (/##) x#    1.0## = x#
   #-}
 

+{-
+We'd like to have more rules, but for example:
+
+This gives wrong answer (0) for NaN - NaN (should be NaN):
+    "minusDouble x x"    forall x#. (-##) x#    x#    = 0.0##
+
+This gives wrong answer (0) for 0 * NaN (should be NaN):
+    "timesDouble 0.0 x"  forall x#. (*##) 0.0## x#    = 0.0##
+
+This gives wrong answer (0) for NaN * 0 (should be NaN):
+    "timesDouble x 0.0"  forall x#. (*##) x#    0.0## = 0.0##
+
+These are tested by num014.
+-}
+

 -- Wrappers for the shift operations.  The uncheckedShift# family are
 -- undefined when the amount being shifted by is greater than the size
 -- in bits of Int#, so these wrappers perform a check and return
 -- Wrappers for the shift operations.  The uncheckedShift# family are
 -- undefined when the amount being shifted by is greater than the size
 -- in bits of Int#, so these wrappers perform a check and return

@@ -818,24 +857,35 @@ gtInt, geInt, eqInt, neInt, ltInt, leInt :: Int -> Int -> Bool
 -- Note that these wrappers still produce undefined results when the
 -- second argument (the shift amount) is negative.
 
 -- Note that these wrappers still produce undefined results when the
 -- second argument (the shift amount) is negative.
 

-shiftL#, shiftRL# :: Word# -> Int# -> Word#
-
+-- | Shift the argument left by the specified number of bits
+-- (which must be non-negative).
+shiftL# :: Word# -> Int# -> Word#

 a `shiftL#` b   | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
 a `shiftL#` b   | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#

-               | otherwise                = a `uncheckedShiftL#` b
+                | otherwise                = a `uncheckedShiftL#` b

 
 

+-- | Shift the argument right by the specified number of bits
+-- (which must be non-negative).
+shiftRL# :: Word# -> Int# -> Word#

 a `shiftRL#` b  | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#
 a `shiftRL#` b  | b >=# WORD_SIZE_IN_BITS# = int2Word# 0#

-               | otherwise                = a `uncheckedShiftRL#` b
-
-iShiftL#, iShiftRA#, iShiftRL# :: Int# -> Int# -> Int#
+                | otherwise                = a `uncheckedShiftRL#` b

 
 

+-- | Shift the argument left by the specified number of bits
+-- (which must be non-negative).
+iShiftL# :: Int# -> Int# -> Int#

 a `iShiftL#` b  | b >=# WORD_SIZE_IN_BITS# = 0#
 a `iShiftL#` b  | b >=# WORD_SIZE_IN_BITS# = 0#

-               | otherwise                = a `uncheckedIShiftL#` b
+                | otherwise                = a `uncheckedIShiftL#` b

 
 

+-- | Shift the argument right (signed) by the specified number of bits
+-- (which must be non-negative).
+iShiftRA# :: Int# -> Int# -> Int#

 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#
 a `iShiftRA#` b | b >=# WORD_SIZE_IN_BITS# = if a <# 0# then (-1#) else 0#

-               | otherwise                = a `uncheckedIShiftRA#` b
+                | otherwise                = a `uncheckedIShiftRA#` b

 
 

+-- | Shift the argument right (unsigned) by the specified number of bits
+-- (which must be non-negative).
+iShiftRL# :: Int# -> Int# -> Int#

 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
 a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#

-               | otherwise                = a `uncheckedIShiftRL#` b
+                | otherwise                = a `uncheckedIShiftRL#` b

 
 #if WORD_SIZE_IN_BITS == 32
 {-# RULES
 
 #if WORD_SIZE_IN_BITS == 32
 {-# RULES

@@ -852,9 +902,9 @@ a `iShiftRL#` b | b >=# WORD_SIZE_IN_BITS# = 0#
 
 
 %********************************************************
 
 
 %********************************************************

-%*                                                     *
+%*                                                      *

 \subsection{Unpacking C strings}
 \subsection{Unpacking C strings}

-%*                                                     *
+%*                                                      *

 %********************************************************
 
 This code is needed for virtually all programs, since it's used for
 %********************************************************
 
 This code is needed for virtually all programs, since it's used for

@@ -862,38 +912,49 @@ unpacking the strings of error messages.
 
 \begin{code}
 unpackCString# :: Addr# -> [Char]
 
 \begin{code}
 unpackCString# :: Addr# -> [Char]

-{-# NOINLINE [1] unpackCString# #-}
+{-# NOINLINE unpackCString# #-}
+    -- There's really no point in inlining this, ever, cos
+    -- the loop doesn't specialise in an interesting
+    -- But it's pretty small, so there's a danger that
+    -- it'll be inlined at every literal, which is a waste

 unpackCString# addr 
   = unpack 0#
   where
     unpack nh
       | ch `eqChar#` '\0'# = []
 unpackCString# addr 
   = unpack 0#
   where
     unpack nh
       | ch `eqChar#` '\0'# = []

-      | otherwise         = C# ch : unpack (nh +# 1#)
+      | otherwise          = C# ch : unpack (nh +# 1#)

       where
       where

-       ch = indexCharOffAddr# addr nh
+        !ch = indexCharOffAddr# addr nh

 
 unpackAppendCString# :: Addr# -> [Char] -> [Char]
 
 unpackAppendCString# :: Addr# -> [Char] -> [Char]

+{-# NOINLINE unpackAppendCString# #-}
+     -- See the NOINLINE note on unpackCString# 

 unpackAppendCString# addr rest
   = unpack 0#
   where
     unpack nh
       | ch `eqChar#` '\0'# = rest
 unpackAppendCString# addr rest
   = unpack 0#
   where
     unpack nh
       | ch `eqChar#` '\0'# = rest

-      | otherwise         = C# ch : unpack (nh +# 1#)
+      | otherwise          = C# ch : unpack (nh +# 1#)

       where
       where

-       ch = indexCharOffAddr# addr nh
+        !ch = indexCharOffAddr# addr nh

 
 unpackFoldrCString# :: Addr# -> (Char  -> a -> a) -> a -> a 
 {-# NOINLINE [0] unpackFoldrCString# #-}
 
 unpackFoldrCString# :: Addr# -> (Char  -> a -> a) -> a -> a 
 {-# NOINLINE [0] unpackFoldrCString# #-}

--- Don't inline till right at the end;
+-- Unlike unpackCString#, there *is* some point in inlining unpackFoldrCString#, 
+-- because we get better code for the function call.
+-- However, don't inline till right at the end;

 -- usually the unpack-list rule turns it into unpackCStringList
 -- usually the unpack-list rule turns it into unpackCStringList

+-- It also has a BuiltInRule in PrelRules.lhs:
+--      unpackFoldrCString# "foo" c (unpackFoldrCString# "baz" c n)
+--        =  unpackFoldrCString# "foobaz" c n

 unpackFoldrCString# addr f z 
   = unpack 0#
   where
     unpack nh
       | ch `eqChar#` '\0'# = z
 unpackFoldrCString# addr f z 
   = unpack 0#
   where
     unpack nh
       | ch `eqChar#` '\0'# = z

-      | otherwise         = C# ch `f` unpack (nh +# 1#)
+      | otherwise          = C# ch `f` unpack (nh +# 1#)

       where
       where

-       ch = indexCharOffAddr# addr nh
+        !ch = indexCharOffAddr# addr nh

 
 unpackCStringUtf8# :: Addr# -> [Char]
 unpackCStringUtf8# addr 
 
 unpackCStringUtf8# :: Addr# -> [Char]
 unpackCStringUtf8# addr 

@@ -918,7 +979,7 @@ unpackCStringUtf8# addr
                      (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
           unpack (nh +# 4#)
       where
                      (ord# (indexCharOffAddr# addr (nh +# 3#)) -# 0x80#))) :
           unpack (nh +# 4#)
       where

-       ch = indexCharOffAddr# addr nh
+        !ch = indexCharOffAddr# addr nh

 
 unpackNBytes# :: Addr# -> Int# -> [Char]
 unpackNBytes# _addr 0#   = []
 
 unpackNBytes# :: Addr# -> Int# -> [Char]
 unpackNBytes# _addr 0#   = []

@@ -927,16 +988,25 @@ unpackNBytes#  addr len# = unpack [] (len# -# 1#)
      unpack acc i#
       | i# <# 0#  = acc
       | otherwise = 
      unpack acc i#
       | i# <# 0#  = acc
       | otherwise = 

-        case indexCharOffAddr# addr i# of
-           ch -> unpack (C# ch : acc) (i# -# 1#)
+         case indexCharOffAddr# addr i# of
+            ch -> unpack (C# ch : acc) (i# -# 1#)

 
 {-# RULES
 
 {-# RULES

-"unpack"       [~1] forall a   . unpackCString# a                 = build (unpackFoldrCString# a)
+"unpack"       [~1] forall a   . unpackCString# a             = build (unpackFoldrCString# a)

 "unpack-list"  [1]  forall a   . unpackFoldrCString# a (:) [] = unpackCString# a
 "unpack-append"     forall a n . unpackFoldrCString# a (:) n  = unpackAppendCString# a n
 
 -- There's a built-in rule (in PrelRules.lhs) for
 "unpack-list"  [1]  forall a   . unpackFoldrCString# a (:) [] = unpackCString# a
 "unpack-append"     forall a n . unpackFoldrCString# a (:) n  = unpackAppendCString# a n
 
 -- There's a built-in rule (in PrelRules.lhs) for

---     unpackFoldr "foo" c (unpackFoldr "baz" c n)  =  unpackFoldr "foobaz" c n
+--      unpackFoldr "foo" c (unpackFoldr "baz" c n)  =  unpackFoldr "foobaz" c n

 
   #-}
 \end{code}
 
   #-}
 \end{code}

+
+#ifdef __HADDOCK__
+\begin{code}
+-- | A special argument for the 'Control.Monad.ST.ST' type constructor,
+-- indexing a state embedded in the 'Prelude.IO' monad by
+-- 'Control.Monad.ST.stToIO'.
+data RealWorld
+\end{code}
+#endif