HORIZON HASKELLDocslts/ghc-9.10.x248f8f02026-10-05Search names, modules, packages, or :: a typeCtrl K

GHC 9.10.3 · lts/ghc-9.10.x · 248f8f0 · 2026-10-05

Moduleinline-c-0.9.1.10Haskell2010

Language.C.Inline.Internal

  • 5 types
  • 19 values

Context handling

2 declarations
valuesetContext :: Context -> Q ()
#

Sets the Context for the current module. This function, if called, must be called before any of the other TH functions in this module. Fails if that's not the case.

Substitution

3 declarations
valuesubstitute :: [(String, String -> String)] -> Q a -> Q a
#

Define macros that can be used in the nested Template Haskell expression. Macros can be used as @MACRO_NAME(input) in inline-c quotes, and will transform their input with the given function. They can be useful for passing in types when defining Haskell instances for C++ template types.

valuegetHaskellType :: Bool -> String -> TypeQ
#

Given a C type name, return the Haskell type in Template Haskell. The first parameter controls whether function pointers should be mapped as pure or IO functions.

Emitting and invoking C code

0 declarations

The functions in this section let us access more the C file associated with the current module. They can be used to build additional features on top of the basic machinery. All of inline-c is based upon the functions defined here.

Emitting C code

valueemitBlock :: QuasiQuoter
#

Simply appends some string of block to the module's C file. Use with care.

Inlining C code

We use the Code data structure to represent some C code that we want to emit to the module's C file and immediately generate a foreign call to. For this reason, Code includes both some C definition, and enough information to be able to generate a foreign call -- specifically the name of the function to call and the Haskell type.

All the quasi-quoters work by constructing a Code and calling inlineCode.

datadata Code
#

Data type representing a list of C definitions with a typed and named entry function.

We use it as a basis to inline and call C code.

Constructors

valueinlineCode :: Code -> ExpQ
#

Inlines a piece of code inline. The resulting Exp will have the type specified in the codeType.

In practice, this function outputs the C code to the module's C file, and then inserts a foreign call of type codeType calling the provided codeFunName.

Example:

c_add :: Int -> Int -> Int
c_add = $(do
  here <- TH.location
  inlineCode $ Code
    TH.Unsafe                   -- Call safety
    (Just here)
    [t| Int -> Int -> Int |]    -- Call type
    "francescos_add"            -- Call name
    -- C Code
    "int francescos_add(int x, int y) { int z = x + y; return z; }")
valueinlineExp
  1. :: Safety

    Safety of the foreign call

  2. -> Loc

    The location to report

  3. -> TypeQ

    Type of the foreign call

  4. -> Type CIdentifier

    Return type of the C expr

  5. -> [(CIdentifier, Type CIdentifier)]

    Parameters of the C expr

  6. -> String

    The C expression

  7. -> ExpQ
#

Same as inlineCItems, but with a single expression.

c_cos :: Double -> Double
c_cos = $(do
  here <- TH.location
  inlineExp
    TH.Unsafe
    here
    [t| Double -> Double |]
    (quickCParser_ "double" parseType)
    [("x", quickCParser_ "double" parseType)]
    "cos(x)")
valueinlineItems
  1. :: Safety

    Safety of the foreign call

  2. -> Bool

    Whether to return as a FunPtr or not

  3. -> Maybe String

    Optional postfix for the generated name

  4. -> Loc

    The location to report

  5. -> TypeQ

    Type of the foreign call

  6. -> Type CIdentifier

    Return type of the C expr

  7. -> [(CIdentifier, Type CIdentifier)]

    Parameters of the C expr

  8. -> String

    The C items

  9. -> ExpQ
#

Same as inlineCode, but accepts a string containing a list of C statements instead instead than a full-blown Code. A function containing the provided statement will be automatically generated.

c_cos :: Double -> Double
c_cos = $(do
 here <- TH.location
 inlineItems
  TH.Unsafe
  False
  Nothing
  here
  [t| Double -> Double |]
  (quickCParser_ "double" parseType)
  [("x", quickCParser_ "double" parseType)]
  "return cos(x);")

Parsing

8 declarations

These functions are used to parse the anti-quotations. They're exposed for testing purposes, you really should not use them.

datadata SomeEq
#
Instances2Eq, Show
  • Eq SomeEqDefined in inline-c-0.9.1.10 · Language.C.Inline.Internal
  • Show SomeEqDefined in inline-c-0.9.1.10 · Language.C.Inline.Internal

Line directives

3 declarations
valuelineDirective :: Loc -> String
#

Tell the C compiler where the next line came from.

Example:

@@ there <- location f (unlines [ lineDirective $(here) , "generated_code_user_did_not_write()" , lineDirective there ] ++ userCode ]) @@

Use lineDirective $(C.here) when generating code, so that any errors or warnings report the location of the generating haskell module, rather than tangentially related user code that doesn't contain the actual problem.

valuehere :: ExpQ
#

Get the location of the code you're looking at, for use with lineDirective; place before generated code that user did not write.

Utility functions for writing quasiquoters

2 declarations