Portability	portable
Stability	experimental
Maintainer	github.com/justinethier
Safe Haskell	None

Language.Scheme.Types

Contents

Environments
Error Handling
Types and related functions

Description

This module contains top-level data type definitions, environments, error types, and associated functions.

Synopsis

Environments

data Env

A Scheme environment containing variable bindings of form (namespaceName, variableName), variableValue

Constructors

Environment
Fields parentEnv :: Maybe Env bindings :: IORef (Map String (IORef LispVal)) pointers :: IORef (Map String (IORef [LispVal]))

Instances

Eq Env

nullEnv :: IO Env

An empty environment

Error Handling

data LispError

Types of errors that may occur when evaluating Scheme code

Constructors

NumArgs (Maybe Integer) [LispVal]	Invalid number of function arguments
TypeMismatch String LispVal	Type error
Parser ParseError	Parsing error
BadSpecialForm String LispVal	Invalid special (built-in) form \| NotFunction String String
UnboundVar String String	A referenced variable has not been declared
DivideByZero	Divide by Zero error
NotImplemented String	Feature is not implemented
InternalError String	An internal error within husk; in theory user (Scheme) code should never allow one of these errors to be triggered.
Default String	Default error

Instances

Show LispError
Error LispError

type ThrowsError = Either LispError

Container used by operations that could throw an error

type IOThrowsError = ErrorT LispError IO

Container used to provide error handling in the IO monad

liftThrows :: ThrowsError a -> IOThrowsError a

Lift a ThrowsError into the IO monad

Types and related functions

data LispVal

Scheme data types

Constructors

Atom String	Symbol
List [LispVal]	List
DottedList [LispVal] LispVal	Pair
Vector (Array Int LispVal)	Vector
ByteVector ByteString	ByteVector from R7RS
HashTable (Map LispVal LispVal)	Hash table. Technically this could be a derived data type instead of being built-in to the interpreter. And perhaps in the future it will be. But for now, a hash table is too important of a data type to not be included.
Number Integer	Integer number
Float Double	Double-precision floating point number
Complex (Complex Double)	Complex number
Rational Rational	Rational number
String String	String
Char Char	Character
Bool Bool	Boolean
PrimitiveFunc ([LispVal] -> ThrowsError LispVal)	Primitive function
Func	Function written in Scheme
Fields params :: [String] vararg :: Maybe String body :: [LispVal] closure :: Env
HFunc	Function formed from a Haskell function
Fields hparams :: [String] hvararg :: Maybe String hbody :: Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal hclosure :: Env
IOFunc ([LispVal] -> IOThrowsError LispVal)	Primitive function within the IO monad
EvalFunc ([LispVal] -> IOThrowsError LispVal)	Function within the IO monad with access to the current environment and continuation.
CustFunc ([LispVal] -> IOThrowsError LispVal)	A custom function written by code outside of husk. Any code that uses the Haskell API should define custom functions using this data type.
Pointer	Pointer to an environment variable.
Fields pointerVar :: String pointerEnv :: Env
Opaque Dynamic	Opaque Haskell value.
Port Handle (Maybe Knob)	I/O port
Continuation	Continuation
Fields contClosure :: Env currentCont :: Maybe DeferredCode nextCont :: Maybe LispVal dynamicWind :: Maybe [DynamicWinders]
Syntax	Type to hold a syntax object that is created by a macro definition. Syntax objects are not used like regular types in that they are not passed around within variables. In other words, you cannot use set! to assign a variable to a syntax object. But they are used during function application. In any case, it is convenient to define the type here because syntax objects are stored in the same environments and manipulated by the same functions as regular variables.
Fields synClosure :: Maybe Env Code env in effect at definition time, if applicable synRenameClosure :: Maybe Env Renames (from macro hygiene) in effect at def time; only applicable if this macro defined inside another macro. synDefinedInMacro :: Bool Set if macro is defined within another macro synEllipsis :: String String to use as the ellipsis identifier synIdentifiers :: [LispVal] Literal identifiers from syntax-rules synRules :: [LispVal] Rules from syntax-rules
SyntaxExplicitRenaming LispVal	Syntax for an explicit-renaming macro
LispEnv Env	Wrapper for a scheme environment
EOF	End of file indicator
Nil String	Internal use only; do not use this type directly.

Instances

Eq LispVal
Ord LispVal
Show LispVal	Allow conversion of lispval instances to strings

nullLisp :: LispVal

Scheme null value

toOpaque :: Typeable a => a -> LispVal

Convert a Haskell value to an opaque Lisp value.

fromOpaque :: forall a. Typeable a => LispVal -> ThrowsError a

Convert an opaque Lisp value back into a Haskell value of the appropriate type, or produce a TypeMismatch error.

data DeferredCode

Container to hold code that is passed to a continuation for deferred execution

Constructors

SchemeBody [LispVal]	A block of Scheme code
HaskellBody	A Haskell function
Fields contFunction :: Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal contFunctionArgs :: Maybe [LispVal]

data DynamicWinders

Container to store information from a dynamic-wind

Constructors

DynamicWinders
Fields before :: LispVal Function to execute when resuming continuation within extent of dynamic-wind after :: LispVal Function to execute when leaving extent of dynamic-wind

Instances

Show DynamicWinders

makeNullContinuation :: Env -> LispVal

Make an empty continuation that does not contain any code

makeCPS

Arguments

:: Env	Environment
-> LispVal	Current continuation
-> (Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal)	Haskell function
-> LispVal	The Haskell function packaged as a LispVal

Make a continuation that takes a higher-order function (written in Haskell)

makeCPSWArgs

Arguments

:: Env	Environment
-> LispVal	Current continuation
-> (Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal)	Haskell function
-> [LispVal]	Arguments to the function
-> LispVal	The Haskell function packaged as a LispVal

Make a continuation that stores a higher-order function and arguments to that function

eqv

Arguments

:: [LispVal]	A list containing two values to compare
-> ThrowsError LispVal	Result wrapped as a Bool

Compare two LispVal instances

eqvList :: ([LispVal] -> ThrowsError LispVal) -> [LispVal] -> ThrowsError LispVal

Compare two lists of haskell values, using the given comparison function

eqVal :: LispVal -> LispVal -> Bool

A more convenient way to call eqv

box :: LispVal -> IOThrowsError [LispVal]

A helper function to make pointer deref code more concise

makeFunc :: Monad m => Maybe String -> Env -> [LispVal] -> [LispVal] -> m LispVal

Create a scheme function

makeNormalFunc :: Monad m => Env -> [LispVal] -> [LispVal] -> m LispVal

Create a normal scheme function

makeVarargs :: Monad m => LispVal -> Env -> [LispVal] -> [LispVal] -> m LispVal

Create a scheme function that can receive any number of arguments

makeHFunc :: Monad m => Maybe String -> Env -> [String] -> (Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal) -> m LispVal

Create a haskell function

makeNormalHFunc :: Monad m => Env -> [String] -> (Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal) -> m LispVal

Create a normal haskell function

makeHVarargs :: Monad m => LispVal -> Env -> [String] -> (Env -> LispVal -> LispVal -> Maybe [LispVal] -> IOThrowsError LispVal) -> m LispVal

Create a haskell function that can receive any number of arguments

validateFuncParams :: [LispVal] -> Maybe Integer -> IOThrowsError Bool

Validate formal function parameters.