| Copyright | (c) The University of Glasgow 2009 |
|---|---|
| License | see libraries/ghc-prim/LICENSE |
| Maintainer | cvs-ghc@haskell.org |
| Stability | internal |
| Portability | non-portable (GHC Extensions) |
| Safe Haskell | None |
| Language | Haskell2010 |
GHC.Types
Description
GHC type definitions. Use GHC.Exts from the base package instead of importing this module directly.
Synopsis
- data Bool
- data Char = C# Char#
- data Int = I# Int#
- data Word = W# Word#
- data Float = F# Float#
- data Double = D# Double#
- data Ordering
- newtype IO a = IO (State# RealWorld -> (# State# RealWorld, a #))
- data List a
- isTrue# :: Int# -> Bool
- data SPEC
- data Symbol
- type family Any :: k where ...
- class a ~# b => (a :: k) ~ (b :: k)
- class a ~# b => (a :: k0) ~~ (b :: k1)
- class a ~R# b => Coercible (a :: k) (b :: k)
- data TYPE (a :: RuntimeRep)
- data CONSTRAINT (a :: RuntimeRep)
- data Levity
- data RuntimeRep
- type LiftedRep = 'BoxedRep 'Lifted
- type UnliftedRep = 'BoxedRep 'Unlifted
- type Type = TYPE LiftedRep
- type UnliftedType = TYPE UnliftedRep
- type Constraint = CONSTRAINT LiftedRep
- type ZeroBitRep = 'TupleRep ('[] :: [RuntimeRep])
- type ZeroBitType = TYPE ZeroBitRep
- data VecCount
- data VecElem
- type Void# = (# #)
- data DictBox a = a => MkDictBox
- data WordBox (a :: TYPE 'WordRep) = MkWordBox a
- data IntBox (a :: TYPE 'IntRep) = MkIntBox a
- data FloatBox (a :: TYPE 'FloatRep) = MkFloatBox a
- data DoubleBox (a :: TYPE 'DoubleRep) = MkDoubleBox a
- data Multiplicity
- type family MultMul (a :: Multiplicity) (b :: Multiplicity) :: Multiplicity where ...
- data Module = Module TrName TrName
- data TrName
- data TyCon = TyCon Word64# Word64# Module TrName Int# KindRep
- data TypeLitSort
- data KindRep
- type KindBndr = Int
Built-in types
The character type Char represents Unicode codespace
and its elements are code points as in definitions
D9 and D10 of the Unicode Standard.
Character literals in Haskell are single-quoted: 'Q', 'Я' or 'Ω'.
To represent a single quote itself use '\'', and to represent a backslash
use '\\'. The full grammar can be found in the section 2.6 of the
Haskell 2010 Language Report.
To specify a character by its code point one can use decimal, hexadecimal
or octal notation: '\65', '\x41' and '\o101' are all alternative forms
of 'A'. The largest code point is '\x10ffff'.
There is a special escape syntax for ASCII control characters:
| Escape | Alternatives | Meaning |
|---|---|---|
'\NUL' | '\0' | null character |
'\SOH' | '\1' | start of heading |
'\STX' | '\2' | start of text |
'\ETX' | '\3' | end of text |
'\EOT' | '\4' | end of transmission |
'\ENQ' | '\5' | enquiry |
'\ACK' | '\6' | acknowledge |
'\BEL' | '\7', '\a' | bell (alert) |
'\BS' | '\8', '\b' | backspace |
'\HT' | '\9', '\t' | horizontal tab |
'\LF' | '\10', '\n' | line feed (new line) |
'\VT' | '\11', '\v' | vertical tab |
'\FF' | '\12', '\f' | form feed |
'\CR' | '\13', '\r' | carriage return |
'\SO' | '\14' | shift out |
'\SI' | '\15' | shift in |
'\DLE' | '\16' | data link escape |
'\DC1' | '\17' | device control 1 |
'\DC2' | '\18' | device control 2 |
'\DC3' | '\19' | device control 3 |
'\DC4' | '\20' | device control 4 |
'\NAK' | '\21' | negative acknowledge |
'\SYN' | '\22' | synchronous idle |
'\ETB' | '\23' | end of transmission block |
'\CAN' | '\24' | cancel |
'\EM' | '\25' | end of medium |
'\SUB' | '\26' | substitute |
'\ESC' | '\27' | escape |
'\FS' | '\28' | file separator |
'\GS' | '\29' | group separator |
'\RS' | '\30' | record separator |
'\US' | '\31' | unit separator |
'\SP' | '\32', ' ' | space |
'\DEL' | '\127' | delete |
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.
Single-precision floating point numbers. It is desirable that this type be at least equal in range and precision to the IEEE single-precision type.
Instances
| Eq Float Source # | Note that due to the presence of
Also note that
|
| Ord Float Source # | See |
Defined in GHC.Classes | |
Double-precision floating point numbers. It is desirable that this type be at least equal in range and precision to the IEEE double-precision type.
Instances
| Eq Double Source # | Note that due to the presence of
Also note that
|
| Ord Double Source # | IEEE 754 IEEE 754-2008, section 5.11 requires that if at least one of arguments of
IEEE 754-2008, section 5.10 defines Thus, users must be extremely cautious when using Moving further, the behaviour of IEEE 754-2008 compliant |
Instances
| Eq Ordering Source # | |
| Ord Ordering Source # | |
Defined in GHC.Classes | |
A value of type IO aa.
There is really only one way to "perform" an I/O action: bind it to
Main.main in your program. When your program is run, the I/O will
be performed. It isn't possible to perform I/O from an arbitrary
function, unless that function is itself in the IO monad and called
at some point, directly or indirectly, from Main.main.
IO is a monad, so IO actions can be combined using either the do-notation
or the >> and >>= operations from the Monad
class.
The builtin list type, usually written in its non-prefix form [a].
Examples
Unless the OverloadedLists extension is enabled, list literals are
syntactic sugar for repeated applications of : and [].
>>>1:2:3:4:[] == [1,2,3,4]True
Similarly, unless the OverloadedStrings extension is enabled, string literals are syntactic sugar for a lists of characters.
>>>['h','e','l','l','o'] == "hello"True
Since: ghc-prim-0.10.0
isTrue# :: Int# -> Bool Source #
Alias for tagToEnum#. Returns True if its parameter is 1# and False
if it is 0#.
SPEC is used by GHC in the SpecConstr pass in order to inform
the compiler when to be particularly aggressive. In particular, it
tells GHC to specialize regardless of size or the number of
specializations. However, not all loops fall into this category.
Libraries can specify this by using SPEC data type to inform which
loops should be aggressively specialized. For example,
instead of
loop x where loop arg = ...
write
loop SPEC x where loop !_ arg = ...
There is no semantic difference between SPEC and SPEC2,
we just need a type with two contructors lest it is optimised away
before SpecConstr.
This type is reexported from GHC.Exts since GHC 9.0 and base-4.15.
For compatibility with earlier releases import it from GHC.Types
in ghc-prim package.
Since: ghc-prim-0.3.1.0
type family Any :: k where ... Source #
The type constructor Any is type to which you can unsafely coerce any
lifted type, and back. More concretely, for a lifted type t and
value x :: t, unsafeCoerce (unsafeCoerce x :: Any) :: t is equivalent
to x.
Type equality
class a ~# b => (a :: k) ~ (b :: k) infix 4 Source #
Lifted, homogeneous equality. By lifted, we mean that it
can be bogus (deferred type error). By homogeneous, the two
types a and b must have the same kinds.
class a ~# b => (a :: k0) ~~ (b :: k1) infix 4 Source #
Lifted, heterogeneous equality. By lifted, we mean that it
can be bogus (deferred type error). By heterogeneous, the two
types a and b might have different kinds. Because ~~ can
appear unexpectedly in error messages to users who do not care
about the difference between heterogeneous equality ~~ and
homogeneous equality ~, this is printed as ~ unless
-fprint-equality-relations is set.
In 0.7.0, the fixity was set to infix 4 to match the fixity of :~~:.
class a ~R# b => Coercible (a :: k) (b :: k) Source #
Coercible is a two-parameter class that has instances for types a and b if
the compiler can infer that they have the same representation. This class
does not have regular instances; instead they are created on-the-fly during
type-checking. Trying to manually declare an instance of Coercible
is an error.
Nevertheless one can pretend that the following three kinds of instances exist. First, as a trivial base-case:
instance Coercible a a
Furthermore, for every type constructor there is
an instance that allows to coerce under the type constructor. For
example, let D be a prototypical type constructor (data or
newtype) with three type arguments, which have roles nominal,
representational resp. phantom. Then there is an instance of
the form
instance Coercible b b' => Coercible (D a b c) (D a b' c')
Note that the nominal type arguments are equal, the
representational type arguments can differ, but need to have a
Coercible instance themself, and the phantom type arguments can be
changed arbitrarily.
The third kind of instance exists for every newtype NT = MkNT T and
comes in two variants, namely
instance Coercible a T => Coercible a NT
instance Coercible T b => Coercible NT b
This instance is only usable if the constructor MkNT is in scope.
If, as a library author of a type constructor like Set a, you
want to prevent a user of your module to write
coerce :: Set T -> Set NT,
you need to set the role of Set's type parameter to nominal,
by writing
type role Set nominal
For more details about this feature, please refer to Safe Coercions by Joachim Breitner, Richard A. Eisenberg, Simon Peyton Jones and Stephanie Weirich.
Since: ghc-prim-0.4.0
Representation polymorphism
data TYPE (a :: RuntimeRep) Source #
data CONSTRAINT (a :: RuntimeRep) Source #
data RuntimeRep Source #
GHC maintains a property that the kind of all inhabited types
(as distinct from type constructors or type-level data) tells us
the runtime representation of values of that type. This datatype
encodes the choice of runtime value.
Note that TYPE is parameterised by RuntimeRep; this is precisely
what we mean by the fact that a type's kind encodes the runtime
representation.
For boxed values (that is, values that are represented by a pointer), a further distinction is made, between lifted types (that contain ⊥), and unlifted ones (that don't).
Constructors
| VecRep VecCount VecElem | a SIMD vector type |
| TupleRep [RuntimeRep] | An unboxed tuple of the given reps |
| SumRep [RuntimeRep] | An unboxed sum of the given reps |
| BoxedRep Levity | boxed; represented by a pointer |
| IntRep | signed, word-sized value |
| Int8Rep | signed, 8-bit value |
| Int16Rep | signed, 16-bit value |
| Int32Rep | signed, 32-bit value |
| Int64Rep | signed, 64-bit value |
| WordRep | unsigned, word-sized value |
| Word8Rep | unsigned, 8-bit value |
| Word16Rep | unsigned, 16-bit value |
| Word32Rep | unsigned, 32-bit value |
| Word64Rep | unsigned, 64-bit value |
| AddrRep | A pointer, but not to a Haskell value |
| FloatRep | a 32-bit floating point number |
| DoubleRep | a 64-bit floating point number |
type UnliftedRep = 'BoxedRep 'Unlifted Source #
The runtime representation of unlifted types.
type UnliftedType = TYPE UnliftedRep Source #
The kind of boxed, unlifted values, for example Array# or a user-defined
unlifted data type, using -XUnliftedDataTypes.
type Constraint = CONSTRAINT LiftedRep Source #
The kind of lifted constraints
type ZeroBitRep = 'TupleRep ('[] :: [RuntimeRep]) Source #
The runtime representation of a zero-width tuple, represented by no bits at all
type ZeroBitType = TYPE ZeroBitRep Source #
The kind of the empty unboxed tuple type (# #)
Element of a SIMD vector type
Boxing constructors
Data type Dict provides a simple way to wrap up a (lifted)
constraint as a type
Constructors
| a => MkDictBox |
Multiplicity types
data Multiplicity Source #
type family MultMul (a :: Multiplicity) (b :: Multiplicity) :: Multiplicity where ... Source #
Runtime type representation
data TypeLitSort Source #
Constructors
| TypeLitSymbol | |
| TypeLitNat | |
| TypeLitChar |
The representation produced by GHC for conjuring up the kind of a
TypeRep.