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4 -- Copyright : (c) The University of Glasgow 2009
5 -- License : see libraries/ghc-prim/LICENSE
7 -- Maintainer : cvs-ghc@haskell.org
8 -- Stability : internal
9 -- Portability : non-portable (GHC Extensions)
11 -- GHC type definitions.
12 -- Use GHC.Exts from the base package instead of importing this
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17 {-# OPTIONS_GHC -XNoImplicitPrelude #-}
19 module GHC.Types (Char(..), Int(..), Float(..), Double(..), IO(..)) where
22 -- We need Inl etc behind the scenes for the type definitions
23 import GHC.Generics ()
27 data [] a = [] | a : [a]
29 {-| The character type 'Char' is an enumeration whose values represent
30 Unicode (or equivalently ISO\/IEC 10646) characters
31 (see <http://www.unicode.org/> for details).
32 This set extends the ISO 8859-1 (Latin-1) character set
33 (the first 256 charachers), which is itself an extension of the ASCII
34 character set (the first 128 characters).
35 A character literal in Haskell has type 'Char'.
37 To convert a 'Char' to or from the corresponding 'Int' value defined
38 by Unicode, use 'Prelude.toEnum' and 'Prelude.fromEnum' from the
39 'Prelude.Enum' class respectively (or equivalently 'ord' and 'chr').
44 -- ^A fixed-precision integer type with at least the range @[-2^29 .. 2^29-1]@.
45 -- The exact range for a given implementation can be determined by using
46 -- 'Prelude.minBound' and 'Prelude.maxBound' from the 'Prelude.Bounded' class.
48 -- | Single-precision floating point numbers.
49 -- It is desirable that this type be at least equal in range and precision
50 -- to the IEEE single-precision type.
51 data Float = F# Float#
53 -- | Double-precision floating point numbers.
54 -- It is desirable that this type be at least equal in range and precision
55 -- to the IEEE double-precision type.
56 data Double = D# Double#
59 A value of type @'IO' a@ is a computation which, when performed,
60 does some I\/O before returning a value of type @a@.
62 There is really only one way to \"perform\" an I\/O action: bind it to
63 @Main.main@ in your program. When your program is run, the I\/O will
64 be performed. It isn't possible to perform I\/O from an arbitrary
65 function, unless that function is itself in the 'IO' monad and called
66 at some point, directly or indirectly, from @Main.main@.
68 'IO' is a monad, so 'IO' actions can be combined using either the do-notation
69 or the '>>' and '>>=' operations from the 'Monad' class.
71 newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))