Foreign.C.Types (original) (raw)

Representations of C types

These types are needed to accurately represent C function prototypes, in order to access C library interfaces in Haskell. The Haskell system is not required to represent those types exactly as C does, but the following guarantees are provided concerning a Haskell type CTrepresenting a C type t:

If a C function prototype has t as an argument or result type, the use of CT in the corresponding position in a foreign declaration permits the Haskell program to access the full range of values encoded by the C type; and conversely, any Haskell value for CT has a valid representation in C.
`[sizeOf](Foreign-Storable.html#v:sizeOf "Foreign.Storable")` (`[undefined](Prelude.html#v:undefined "Prelude")` :: CT) will yield the same value assizeof (t) in C.
`[alignment](Foreign-Storable.html#v:alignment "Foreign.Storable")` (`[undefined](Prelude.html#v:undefined "Prelude")` :: CT) matches the alignment constraint enforced by the C implementation for t.
The members [peek](Foreign-Storable.html#v:peek "Foreign.Storable") and [poke](Foreign-Storable.html#v:poke "Foreign.Storable") of the [Storable](Foreign-Storable.html#t:Storable "Foreign.Storable") class map all values of CT to the corresponding value of t and vice versa.
When an instance of [Bounded](Prelude.html#v:Bounded "Prelude") is defined for CT, the values of [minBound](Prelude.html#v:minBound "Prelude") and [maxBound](Prelude.html#v:maxBound "Prelude") coincide with t_MIN and t_MAX in C.
When an instance of [Eq](Prelude.html#v:Eq "Prelude") or [Ord](Prelude.html#v:Ord "Prelude") is defined for CT, the predicates defined by the type class implement the same relation as the corresponding predicate in C on t.
When an instance of [Num](Prelude.html#v:Num "Prelude"), [Read](Prelude.html#v:Read "Prelude"), [Integral](Prelude.html#v:Integral "Prelude"),[Fractional](Prelude.html#v:Fractional "Prelude"), [Floating](Prelude.html#v:Floating "Prelude"), [RealFrac](Prelude.html#v:RealFrac "Prelude"), or[RealFloat](Prelude.html#v:RealFloat "Prelude") is defined for CT, the arithmetic operations defined by the type class implement the same function as the corresponding arithmetic operations (if available) in C on t.
When an instance of [Bits](GHC-Bits.html#t:Bits "GHC.Bits") is defined for CT, the bitwise operation defined by the type class implement the same function as the corresponding bitwise operation in C on t.

Platform differences

This module contains platform specific information about types.As such, the types presented on this page reflect the platform on which the documentation was generated and may not coincide with the types on your platform.

Integral types

These types are represented as newtypes of types in Data.Int and Data.Word, and are instances of[Eq](Prelude.html#v:Eq "Prelude"), [Ord](Prelude.html#v:Ord "Prelude"), [Num](Prelude.html#v:Num "Prelude"), [Read](Prelude.html#v:Read "Prelude"),[Show](Prelude.html#v:Show "Prelude"), [Enum](Prelude.html#v:Enum "Prelude"), [Typeable](Data-Typeable.html#v:Typeable "Data.Typeable"),[Storable](Foreign-Storable.html#t:Storable "Foreign.Storable"), [Bounded](Prelude.html#v:Bounded "Prelude"), [Real](Prelude.html#v:Real "Prelude"), [Integral](Prelude.html#v:Integral "Prelude") and [Bits](GHC-Bits.html#t:Bits "GHC.Bits").

newtype CUChar Source #

Haskell type representing the C unsigned char type.(The concrete types of Foreign.C.Types are platform-specific.)

newtype CUInt Source #

Haskell type representing the C unsigned int type.(The concrete types of Foreign.C.Types are platform-specific.)

newtype CULong Source #

Haskell type representing the C unsigned long type.(The concrete types of Foreign.C.Types are platform-specific.)

newtype CULLong Source #

Haskell type representing the C unsigned long long type.(The concrete types of Foreign.C.Types are platform-specific.)

newtype CBool Source #

Haskell type representing the C bool type.(The concrete types of Foreign.C.Types are platform-specific.)

Since: base-4.10.0.0

Numeric types

newtype CUSeconds Source #

Haskell type representing the C useconds_t type.(The concrete types of Foreign.C.Types are platform-specific.)

Since: base-4.4.0.0

newtype CSUSeconds Source #

Haskell type representing the C suseconds_t type.(The concrete types of Foreign.C.Types are platform-specific.)

Since: base-4.4.0.0

To convert [CTime](Foreign-C-Types.html#t:CTime "Foreign.C.Types") to [UTCTime](Data-Time.html#v:UTCTime "Data.Time"), use the following:

\t -> posixSecondsToUTCTime (realToFrac t :: POSIXTime)

Floating types

These types are represented as newtypes of[Float](Prelude.html#v:Float "Prelude") and [Double](Prelude.html#v:Double "Prelude"), and are instances of[Eq](Prelude.html#v:Eq "Prelude"), [Ord](Prelude.html#v:Ord "Prelude"), [Num](Prelude.html#v:Num "Prelude"), [Read](Prelude.html#v:Read "Prelude"),[Show](Prelude.html#v:Show "Prelude"), [Enum](Prelude.html#v:Enum "Prelude"), [Typeable](Data-Typeable.html#v:Typeable "Data.Typeable"), [Storable](Foreign-Storable.html#t:Storable "Foreign.Storable"),[Real](Prelude.html#v:Real "Prelude"), [Fractional](Prelude.html#v:Fractional "Prelude"), [Floating](Prelude.html#v:Floating "Prelude"),[RealFrac](Prelude.html#v:RealFrac "Prelude") and [RealFloat](Prelude.html#v:RealFloat "Prelude"). That does mean that [CFloat](Foreign-C-Types.html#t:CFloat "Foreign.C.Types")'s (respectively [CDouble](Foreign-C-Types.html#t:CDouble "Foreign.C.Types")'s) instances of[Eq](Prelude.html#v:Eq "Prelude"), [Ord](Prelude.html#v:Ord "Prelude"), [Num](Prelude.html#v:Num "Prelude") and[Fractional](Prelude.html#v:Fractional "Prelude") are as badly behaved as [Float](Prelude.html#v:Float "Prelude")'s (respectively [Double](Prelude.html#v:Double "Prelude")'s).

Other types