base-4.2.0.0: Basic librariesContentsIndex
Foreign.C.Types
Portabilityportable
Stabilityprovisional
Maintainerffi@haskell.org
Contents
Representations of C types
Integral types
Numeric types
Floating types
Other types
Description
Mapping of C types to corresponding Haskell types.
Synopsis
data CChar
data CSChar
data CUChar
data CShort
data CUShort
data CInt
data CUInt
data CLong
data CULong
data CPtrdiff
data CSize
data CWchar
data CSigAtomic
data CLLong
data CULLong
data CIntPtr
data CUIntPtr
data CIntMax
data CUIntMax
data CClock
data CTime
data CFloat
data CDouble
data CFile
data CFpos
data CJmpBuf
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 CT representing 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 (Prelude.undefined :: CT) will yield the same value as sizeof (t) in C.
  • alignment (Prelude.undefined :: CT) matches the alignment constraint enforced by the C implementation for t.
  • The members peek and poke of the Storable class map all values of CT to the corresponding value of t and vice versa.
  • When an instance of Prelude.Bounded is defined for CT, the values of Prelude.minBound and Prelude.maxBound coincide with t_MIN and t_MAX in C.
  • When an instance of Prelude.Eq or Prelude.Ord 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 Prelude.Num, Prelude.Read, Prelude.Integral, Prelude.Fractional, Prelude.Floating, Prelude.RealFrac, or Prelude.RealFloat 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 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.
Integral types
These types are are represented as newtypes of types in Data.Int and Data.Word, and are instances of Prelude.Eq, Prelude.Ord, Prelude.Num, Prelude.Read, Prelude.Show, Prelude.Enum, Typeable, Storable, Prelude.Bounded, Prelude.Real, Prelude.Integral and Bits.
data CChar
Haskell type representing the C char type.
data CSChar
Haskell type representing the C signed char type.
data CUChar
Haskell type representing the C unsigned char type.
data CShort
Haskell type representing the C short type.
data CUShort
Haskell type representing the C unsigned short type.
data CInt
Haskell type representing the C int type.
data CUInt
Haskell type representing the C unsigned int type.
data CLong
Haskell type representing the C long type.
data CULong
Haskell type representing the C unsigned long type.
data CPtrdiff
Haskell type representing the C ptrdiff_t type.
data CSize
Haskell type representing the C size_t type.
data CWchar
Haskell type representing the C wchar_t type.
data CSigAtomic
Haskell type representing the C sig_atomic_t type.
data CLLong
Haskell type representing the C long long type.
data CULLong
Haskell type representing the C unsigned long long type.
data CIntPtr
data CUIntPtr
data CIntMax
data CUIntMax
Numeric types
These types are are represented as newtypes of basic foreign types, and are instances of Prelude.Eq, Prelude.Ord, Prelude.Num, Prelude.Read, Prelude.Show, Prelude.Enum, Typeable and Storable.
data CClock
Haskell type representing the C clock_t type.
data CTime

Haskell type representing the C time_t type.

To convert to a Data.Time.UTCTime, use the following formula:

  posixSecondsToUTCTime (realToFrac :: POSIXTime)
Floating types
These types are are represented as newtypes of Prelude.Float and Prelude.Double, and are instances of Prelude.Eq, Prelude.Ord, Prelude.Num, Prelude.Read, Prelude.Show, Prelude.Enum, Typeable, Storable, Prelude.Real, Prelude.Fractional, Prelude.Floating, Prelude.RealFrac and Prelude.RealFloat.
data CFloat
Haskell type representing the C float type.
data CDouble
Haskell type representing the C double type.
Other types
data CFile
Haskell type representing the C FILE type.
data CFpos
Haskell type representing the C fpos_t type.
data CJmpBuf
Haskell type representing the C jmp_buf type.
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