Documentation.Haddock

The Haddock API: A rudimentory, highly experimental API exposing some of the internals of Haddock. Don't expect it to be stable.

Interface

data Interface

Interface holds all information used to render a single Haddock page. It represents the interface of a module. The core business of Haddock lies in creating this structure. Note that the record contains some fields that are only used to create the final record, and that are not used by the backends.

Constructors

Interface

Fields

• ifaceMod :: !Module

  The module behind this interface.

• ifaceIsSig :: !Bool

  Is this a signature?

• ifaceOrigFilename :: !FilePath

  Original file name of the module.

• ifaceInfo :: !(HaddockModInfo Name)

  Textual information about the module.

• ifaceDoc :: !(Documentation Name)

  Documentation header.

• ifaceRnDoc :: !(Documentation DocName)

  Documentation header with cross-reference information.

• ifaceOptions :: ![DocOption]

  Haddock options for this module (prune, ignore-exports, etc).

• ifaceDeclMap :: !(Map Name [LHsDecl GhcRn])

  Declarations originating from the module. Excludes declarations without names (instances and stand-alone documentation comments). Includes names of subordinate declarations mapped to their parent declarations.

• ifaceDocMap :: !(DocMap Name)

  Documentation of declarations originating from the module (including subordinates).

• ifaceArgMap :: !(ArgMap Name)
• ifaceRnDocMap :: !(DocMap DocName)

  Documentation of declarations originating from the module (including subordinates).

• ifaceRnArgMap :: !(ArgMap DocName)
• ifaceFixMap :: !(Map Name Fixity)
• ifaceExportItems :: ![ExportItem GhcRn]
• ifaceRnExportItems :: ![ExportItem DocNameI]
• ifaceExports :: ![Name]

  All names exported by the module.

• ifaceVisibleExports :: ![Name]

  All "visible" names exported by the module. A visible name is a name that will show up in the documentation of the module.

• ifaceModuleAliases :: !AliasMap

  Aliases of module imports as in import A.B.C as C.

• ifaceInstances :: ![ClsInst]

  Instances exported by the module.

• ifaceFamInstances :: ![FamInst]
• ifaceOrphanInstances :: ![DocInstance GhcRn]

  Orphan instances

• ifaceRnOrphanInstances :: ![DocInstance DocNameI]
• ifaceHaddockCoverage :: !(Int, Int)

  The number of haddockable and haddocked items in the module, as a tuple. Haddockable items are the exports and the module itself.

• ifaceWarningMap :: !WarningMap

  Warnings for things defined in this module.

• ifaceHieFile :: !(Maybe FilePath)

  Tokenized source code of module (avaliable if Haddock is invoked with source generation flag).

• ifaceDynFlags :: !DynFlags

data InstalledInterface

A subset of the fields of Interface that we store in the interface files.

Constructors

InstalledInterface

Fields

• instMod :: Module

  The module represented by this interface.

• instIsSig :: Bool

  Is this a signature?

• instInfo :: HaddockModInfo Name

  Textual information about the module.

• instDocMap :: DocMap Name

  Documentation of declarations originating from the module (including subordinates).

• instArgMap :: ArgMap Name
• instExports :: [Name]

  All names exported by this module.

• instVisibleExports :: [Name]

  All "visible" names exported by the module. A visible name is a name that will show up in the documentation of the module.

• instOptions :: [DocOption]

  Haddock options for this module (prune, ignore-exports, etc).

• instFixMap :: Map Name Fixity

Instances

Binary InstalledInterface

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> InstalledInterface -> IO ()

put :: BinHandle -> InstalledInterface -> IO (Bin InstalledInterface)

get :: BinHandle -> IO InstalledInterface

toInstalledIface :: Interface -> InstalledInterface

Convert an Interface to an InstalledInterface

createInterfaces

Arguments

:: [Flag]

A list of command-line flags

-> [String]

File or module names

-> IO [Interface]

Resulting list of interfaces

Create Interface structures from a given list of Haddock command-line flags and file or module names (as accepted by haddock executable). Flags that control documentation generation or show help or version information are ignored.

processModules

Arguments

:: Verbosity

Verbosity of logging to stdout

-> [String]

A list of file or module names sorted by module topology

-> [Flag]

Command-line flags

-> [InterfaceFile]

Interface files of package dependencies

-> Ghc ([Interface], LinkEnv)

Resulting list of interfaces and renaming environment

Create Interfaces and a link environment by typechecking the list of modules using the GHC API and processing the resulting syntax trees.

Export items & declarations

data ExportItem name

Constructors

ExportDecl

An exported declaration.

Fields

• expItemDecl :: !(LHsDecl name)

  A declaration.

• expItemPats :: ![(HsDecl name, DocForDecl (IdP name))]

  Bundled patterns for a data type declaration

• expItemMbDoc :: !(DocForDecl (IdP name))

  Maybe a doc comment, and possibly docs for arguments (if this decl is a function or type-synonym).

• expItemSubDocs :: ![(IdP name, DocForDecl (IdP name))]

  Subordinate names, possibly with documentation.

• expItemInstances :: ![DocInstance name]

  Instances relevant to this declaration, possibly with documentation.

• expItemFixities :: ![(IdP name, Fixity)]

  Fixity decls relevant to this declaration (including subordinates).

• expItemSpliced :: !Bool

  Whether the ExportItem is from a TH splice or not, for generating the appropriate type of Source link.

ExportNoDecl

An exported entity for which we have no documentation (perhaps because it resides in another package).

Fields

• expItemName :: !(IdP name)
• expItemSubs :: ![IdP name]

  Subordinate names.

ExportGroup

A section heading.

Fields

• expItemSectionLevel :: !Int

  Section level (1, 2, 3, ...).

• expItemSectionId :: !String

  Section id (for hyperlinks).

• expItemSectionText :: !(Doc (IdP name))

  Section heading text.

ExportDoc !(MDoc (IdP name))

Some documentation.

ExportModule !Module

A cross-reference to another module.

type DocForDecl name = (Documentation name, FnArgsDoc name)

type FnArgsDoc name = Map Int (MDoc name)

Arguments and result are indexed by Int, zero-based from the left, because that's the easiest to use when recursing over types.

Cross-referencing

type LinkEnv = Map Name Module

Type of environment used to cross-reference identifiers in the syntax.

data DocName

Extends Name with cross-reference information.

Constructors

Documented Name Module

This thing is part of the (existing or resulting) documentation. The Module is the preferred place in the documentation to refer to.

Undocumented Name

This thing is not part of the (existing or resulting) documentation, as far as Haddock knows.

Instances

Eq DocName

Defined in Haddock.Types

Methods

(==) :: DocName -> DocName -> Bool

(/=) :: DocName -> DocName -> Bool

Data DocName

Defined in Haddock.Types

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> DocName -> c DocName

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c DocName

toConstr :: DocName -> Constr

dataTypeOf :: DocName -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c DocName)

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c DocName)

gmapT :: (forall b. Data b => b -> b) -> DocName -> DocName

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> DocName -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> DocName -> r

gmapQ :: (forall d. Data d => d -> u) -> DocName -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> DocName -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> DocName -> m DocName

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> DocName -> m DocName

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> DocName -> m DocName

NamedThing DocName

Defined in Haddock.Types

Methods

getOccName :: DocName -> OccName

getName :: DocName -> Name

HasOccName DocName

Defined in Haddock.Types

Methods

occName :: DocName -> OccName

Binary DocName

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> DocName -> IO ()

put :: BinHandle -> DocName -> IO (Bin DocName)

get :: BinHandle -> IO DocName

Outputable DocName

Useful for debugging

Defined in Haddock.Types

Methods

ppr :: DocName -> SDoc

pprPrec :: Rational -> DocName -> SDoc

OutputableBndr DocName

Defined in Haddock.Types

Methods

pprBndr :: BindingSite -> DocName -> SDoc

pprPrefixOcc :: DocName -> SDoc

pprInfixOcc :: DocName -> SDoc

bndrIsJoin_maybe :: DocName -> Maybe Int

Instances

type DocInstance name = (InstHead name, Maybe (MDoc (IdP name)), Located (IdP name), Maybe Module)

An instance head that may have documentation and a source location.

data InstHead name

The head of an instance. Consists of a class name, a list of type parameters (which may be annotated with kinds), and an instance type

Documentation comments

type Doc id = DocH (Wrap (ModuleName, OccName)) (Wrap id)

type MDoc id = MetaDoc (Wrap (ModuleName, OccName)) (Wrap id)

data DocH mod id

Constructors

DocEmpty

DocAppend (DocH mod id) (DocH mod id)

DocString String

DocParagraph (DocH mod id)

DocIdentifier id

DocIdentifierUnchecked mod

A qualified identifier that couldn't be resolved.

DocModule (ModLink (DocH mod id))

A link to a module, with an optional label.

DocWarning (DocH mod id)

This constructor has no counterpart in Haddock markup.

DocEmphasis (DocH mod id)

DocMonospaced (DocH mod id)

DocBold (DocH mod id)

DocUnorderedList [DocH mod id]

DocOrderedList [DocH mod id]

DocDefList [(DocH mod id, DocH mod id)]

DocCodeBlock (DocH mod id)

DocHyperlink (Hyperlink (DocH mod id))

DocPic Picture

DocMathInline String

DocMathDisplay String

DocAName String

A (HTML) anchor. It must not contain any spaces.

DocProperty String

DocExamples [Example]

DocHeader (Header (DocH mod id))

DocTable (Table (DocH mod id))

Instances

Bitraversable DocH

NOTE: Only defined for base >= 4.10.0

Defined in Documentation.Haddock.Types

Methods

bitraverse :: Applicative f => (a -> f c) -> (b -> f d) -> DocH a b -> f (DocH c d)

Bifoldable DocH

NOTE: Only defined for base >= 4.10.0

Defined in Documentation.Haddock.Types

Methods

bifold :: Monoid m => DocH m m -> m

bifoldMap :: Monoid m => (a -> m) -> (b -> m) -> DocH a b -> m

bifoldr :: (a -> c -> c) -> (b -> c -> c) -> c -> DocH a b -> c

bifoldl :: (c -> a -> c) -> (c -> b -> c) -> c -> DocH a b -> c

Bifunctor DocH

NOTE: Only defined for base >= 4.8.0

Defined in Documentation.Haddock.Types

Methods

bimap :: (a -> b) -> (c -> d) -> DocH a c -> DocH b d

first :: (a -> b) -> DocH a c -> DocH b c

second :: (b -> c) -> DocH a b -> DocH a c

Functor (DocH mod)

Defined in Documentation.Haddock.Types

Methods

fmap :: (a -> b) -> DocH mod a -> DocH mod b

(<$) :: a -> DocH mod b -> DocH mod a

Foldable (DocH mod)

Defined in Documentation.Haddock.Types

Methods

fold :: Monoid m => DocH mod m -> m

foldMap :: Monoid m => (a -> m) -> DocH mod a -> m

foldMap' :: Monoid m => (a -> m) -> DocH mod a -> m

foldr :: (a -> b -> b) -> b -> DocH mod a -> b

foldr' :: (a -> b -> b) -> b -> DocH mod a -> b

foldl :: (b -> a -> b) -> b -> DocH mod a -> b

foldl' :: (b -> a -> b) -> b -> DocH mod a -> b

foldr1 :: (a -> a -> a) -> DocH mod a -> a

foldl1 :: (a -> a -> a) -> DocH mod a -> a

toList :: DocH mod a -> [a]

null :: DocH mod a -> Bool

length :: DocH mod a -> Int

elem :: Eq a => a -> DocH mod a -> Bool

maximum :: Ord a => DocH mod a -> a

minimum :: Ord a => DocH mod a -> a

sum :: Num a => DocH mod a -> a

product :: Num a => DocH mod a -> a

Traversable (DocH mod)

Defined in Documentation.Haddock.Types

Methods

traverse :: Applicative f => (a -> f b) -> DocH mod a -> f (DocH mod b)

sequenceA :: Applicative f => DocH mod (f a) -> f (DocH mod a)

mapM :: Monad m => (a -> m b) -> DocH mod a -> m (DocH mod b)

sequence :: Monad m => DocH mod (m a) -> m (DocH mod a)

(Eq id, Eq mod) => Eq (DocH mod id)

Defined in Documentation.Haddock.Types

Methods

(==) :: DocH mod id -> DocH mod id -> Bool

(/=) :: DocH mod id -> DocH mod id -> Bool

(Show id, Show mod) => Show (DocH mod id)

Defined in Documentation.Haddock.Types

Methods

showsPrec :: Int -> DocH mod id -> ShowS

show :: DocH mod id -> String

showList :: [DocH mod id] -> ShowS

(NFData a, NFData mod) => NFData (DocH mod a)

Defined in Haddock.Types

Methods

rnf :: DocH mod a -> ()

(Binary mod, Binary id) => Binary (DocH mod id)

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> DocH mod id -> IO ()

put :: BinHandle -> DocH mod id -> IO (Bin (DocH mod id))

get :: BinHandle -> IO (DocH mod id)

data Example

Constructors

Example

Fields

• exampleExpression :: String
• exampleResult :: [String]

Instances

Eq Example

Defined in Documentation.Haddock.Types

Methods

(==) :: Example -> Example -> Bool

(/=) :: Example -> Example -> Bool

Show Example

Defined in Documentation.Haddock.Types

Methods

showsPrec :: Int -> Example -> ShowS

show :: Example -> String

showList :: [Example] -> ShowS

NFData Example

Defined in Haddock.Types

Methods

rnf :: Example -> ()

Binary Example

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> Example -> IO ()

put :: BinHandle -> Example -> IO (Bin Example)

get :: BinHandle -> IO Example

data Hyperlink id

Constructors

Hyperlink

Fields

• hyperlinkUrl :: String
• hyperlinkLabel :: Maybe id

Instances

Functor Hyperlink

Defined in Documentation.Haddock.Types

Methods

fmap :: (a -> b) -> Hyperlink a -> Hyperlink b

(<$) :: a -> Hyperlink b -> Hyperlink a

Foldable Hyperlink

Defined in Documentation.Haddock.Types

Methods

fold :: Monoid m => Hyperlink m -> m

foldMap :: Monoid m => (a -> m) -> Hyperlink a -> m

foldMap' :: Monoid m => (a -> m) -> Hyperlink a -> m

foldr :: (a -> b -> b) -> b -> Hyperlink a -> b

foldr' :: (a -> b -> b) -> b -> Hyperlink a -> b

foldl :: (b -> a -> b) -> b -> Hyperlink a -> b

foldl' :: (b -> a -> b) -> b -> Hyperlink a -> b

foldr1 :: (a -> a -> a) -> Hyperlink a -> a

foldl1 :: (a -> a -> a) -> Hyperlink a -> a

toList :: Hyperlink a -> [a]

null :: Hyperlink a -> Bool

length :: Hyperlink a -> Int

elem :: Eq a => a -> Hyperlink a -> Bool

maximum :: Ord a => Hyperlink a -> a

minimum :: Ord a => Hyperlink a -> a

sum :: Num a => Hyperlink a -> a

product :: Num a => Hyperlink a -> a

Traversable Hyperlink

Defined in Documentation.Haddock.Types

Methods

traverse :: Applicative f => (a -> f b) -> Hyperlink a -> f (Hyperlink b)

sequenceA :: Applicative f => Hyperlink (f a) -> f (Hyperlink a)

mapM :: Monad m => (a -> m b) -> Hyperlink a -> m (Hyperlink b)

sequence :: Monad m => Hyperlink (m a) -> m (Hyperlink a)

Eq id => Eq (Hyperlink id)

Defined in Documentation.Haddock.Types

Methods

(==) :: Hyperlink id -> Hyperlink id -> Bool

(/=) :: Hyperlink id -> Hyperlink id -> Bool

Show id => Show (Hyperlink id)

Defined in Documentation.Haddock.Types

Methods

showsPrec :: Int -> Hyperlink id -> ShowS

show :: Hyperlink id -> String

showList :: [Hyperlink id] -> ShowS

NFData id => NFData (Hyperlink id)

Defined in Haddock.Types

Methods

rnf :: Hyperlink id -> ()

Binary a => Binary (Hyperlink a)

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> Hyperlink a -> IO ()

put :: BinHandle -> Hyperlink a -> IO (Bin (Hyperlink a))

get :: BinHandle -> IO (Hyperlink a)

type DocMarkup id a = DocMarkupH (Wrap (ModuleName, OccName)) id a

data DocMarkupH mod id a

DocMarkupH is a set of instructions for marking up documentation. In fact, it's really just a mapping from Doc to some other type [a], where [a] is usually the type of the output (HTML, say). Use markup to apply a DocMarkupH to a DocH.

Since: haddock-library-1.4.5

Constructors

Markup

Fields

• markupEmpty :: a
• markupString :: String -> a
• markupParagraph :: a -> a
• markupAppend :: a -> a -> a
• markupIdentifier :: id -> a
• markupIdentifierUnchecked :: mod -> a
• markupModule :: ModLink a -> a
• markupWarning :: a -> a
• markupEmphasis :: a -> a
• markupBold :: a -> a
• markupMonospaced :: a -> a
• markupUnorderedList :: [a] -> a
• markupOrderedList :: [a] -> a
• markupDefList :: [(a, a)] -> a
• markupCodeBlock :: a -> a
• markupHyperlink :: Hyperlink a -> a
• markupAName :: String -> a
• markupPic :: Picture -> a
• markupMathInline :: String -> a
• markupMathDisplay :: String -> a
• markupProperty :: String -> a
• markupExample :: [Example] -> a
• markupHeader :: Header a -> a
• markupTable :: Table a -> a

data Documentation name

Constructors

Documentation

Fields

• documentationDoc :: Maybe (MDoc name)
• documentationWarning :: !(Maybe (Doc name))

Instances

Functor Documentation

Defined in Haddock.Types

Methods

fmap :: (a -> b) -> Documentation a -> Documentation b

(<$) :: a -> Documentation b -> Documentation a

type ArgMap a = Map Name (Map Int (MDoc a))

type AliasMap = Map Module ModuleName

type WarningMap = Map Name (Doc Name)

type DocMap a = Map Name (MDoc a)

data HaddockModInfo name

Constructors

HaddockModInfo

Fields

• hmi_description :: Maybe (Doc name)
• hmi_copyright :: Maybe String
• hmi_license :: Maybe String
• hmi_maintainer :: Maybe String
• hmi_stability :: Maybe String
• hmi_portability :: Maybe String
• hmi_safety :: Maybe String
• hmi_language :: Maybe Language
• hmi_extensions :: [Extension]

Instances

Binary name => Binary (HaddockModInfo name)

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> HaddockModInfo name -> IO ()

put :: BinHandle -> HaddockModInfo name -> IO (Bin (HaddockModInfo name))

get :: BinHandle -> IO (HaddockModInfo name)

markup :: DocMarkupH mod id a -> DocH mod id -> a

Interface files

data InterfaceFile

Constructors

InterfaceFile

Fields

• ifLinkEnv :: LinkEnv
• ifInstalledIfaces :: [InstalledInterface]

Instances

Binary InterfaceFile

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> InterfaceFile -> IO ()

put :: BinHandle -> InterfaceFile -> IO (Bin InterfaceFile)

get :: BinHandle -> IO InterfaceFile

readInterfaceFile

Arguments

:: forall m. MonadIO m

=> NameCacheAccessor m

-> FilePath

-> Bool

Disable version check. Can cause runtime crash.

-> m (Either String InterfaceFile)

Read a Haddock (.haddock) interface file. Return either an InterfaceFile or an error message.

This function can be called in two ways. Within a GHC session it will update the use and update the session's name cache. Outside a GHC session a new empty name cache is used. The function is therefore generic in the monad being used. The exact monad is whichever monad the first argument, the getter and setter of the name cache, requires.

nameCacheFromGhc :: GhcMonad m => NameCacheAccessor m

freshNameCache :: NameCacheAccessor IO

type NameCacheAccessor m = (m NameCache, NameCache -> m ())

Flags and options

data Flag

Constructors

Flag_BuiltInThemes

Flag_CSS String

Flag_ReadInterface String

Flag_DumpInterface String

Flag_ShowInterface String

Flag_Heading String

Flag_Html

Flag_Hoogle

Flag_Lib String

Flag_OutputDir FilePath

Flag_Prologue FilePath

Flag_SourceBaseURL String

Flag_SourceModuleURL String

Flag_SourceEntityURL String

Flag_SourceLEntityURL String

Flag_WikiBaseURL String

Flag_WikiModuleURL String

Flag_WikiEntityURL String

Flag_LaTeX

Flag_LaTeXStyle String

Flag_QuickJumpIndex

Flag_HyperlinkedSource

Flag_SourceCss String

Flag_Mathjax String

Flag_Help

Flag_Verbosity String

Flag_Version

Flag_CompatibleInterfaceVersions

Flag_InterfaceVersion

Flag_BypassInterfaceVersonCheck

Flag_UseContents String

Flag_GenContents

Flag_UseIndex String

Flag_GenIndex

Flag_IgnoreAllExports

Flag_HideModule String

Flag_ShowModule String

Flag_ShowAllModules

Flag_ShowExtensions String

Flag_OptGhc String

Flag_GhcLibDir String

Flag_GhcVersion

Flag_PrintGhcPath

Flag_PrintGhcLibDir

Flag_NoWarnings

Flag_UseUnicode

Flag_NoTmpCompDir

Flag_Qualification String

Flag_PrettyHtml

Flag_NoPrintMissingDocs

Flag_PackageName String

Flag_PackageVersion String

Flag_Reexport String

Flag_SinceQualification String

Flag_IgnoreLinkSymbol String

Instances

Eq Flag

Defined in Haddock.Options

Methods

(==) :: Flag -> Flag -> Bool

(/=) :: Flag -> Flag -> Bool

Show Flag

Defined in Haddock.Options

Methods

showsPrec :: Int -> Flag -> ShowS

show :: Flag -> String

showList :: [Flag] -> ShowS

data DocOption

Source-level options for controlling the documentation.

Constructors

OptHide

This module should not appear in the docs.

OptPrune

OptIgnoreExports

Pretend everything is exported.

OptNotHome

Not the best place to get docs for things exported by this module.

OptShowExtensions

Render enabled extensions for this module.

Instances

Eq DocOption

Defined in Haddock.Types

Methods

(==) :: DocOption -> DocOption -> Bool

(/=) :: DocOption -> DocOption -> Bool

Show DocOption

Defined in Haddock.Types

Methods

showsPrec :: Int -> DocOption -> ShowS

show :: DocOption -> String

showList :: [DocOption] -> ShowS

Binary DocOption

Defined in Haddock.InterfaceFile

Methods

put_ :: BinHandle -> DocOption -> IO ()

put :: BinHandle -> DocOption -> IO (Bin DocOption)

get :: BinHandle -> IO DocOption

Error handling

data HaddockException

Haddock's own exception type.

Constructors

HaddockException String

WithContext [String] SomeException

Instances

Show HaddockException

Defined in Haddock.Types

Methods

showsPrec :: Int -> HaddockException -> ShowS

show :: HaddockException -> String

showList :: [HaddockException] -> ShowS

Exception HaddockException

Defined in Haddock.Types

Methods

toException :: HaddockException -> SomeException

fromException :: SomeException -> Maybe HaddockException

displayException :: HaddockException -> String

Program entry point

haddock :: [String] -> IO ()

Run Haddock with given list of arguments.

Haddock's own main function is defined in terms of this:

main = getArgs >>= haddock

haddockWithGhc :: (forall a. [Flag] -> Ghc a -> IO a) -> [String] -> IO ()

getGhcDirs :: [Flag] -> IO (Maybe FilePath, Maybe FilePath)

Find the lib directory for GHC and the path to ghc

withGhc :: [Flag] -> Ghc a -> IO a