Safe Haskell	None
Language	GHC2021

Howl.Eval.Context

Description

Core evaluation context types and operations.

This module defines the evaluator context, rules, declarations, attributes, and lower-level operations for running and extending Howl evaluation.

Synopsis

data Rule
- = PatRule Pat Expr
- | BuiltinRule (Expr -> Eval (Maybe Expr))
data Context = MkContext {
- symbolRecordTable :: !(HashTable Symbol SymbolRecord)
- moduleNumberRef :: !(IORef Int)
- lineNumberRef :: !(IORef Int)
- errorLineHandlerRef :: !(IORef (Text -> IO ()))
- outputLineHandlerRef :: !(IORef (Text -> IO ()))
- addToEvalCacheHandler :: Expr -> Eval ()
- returnIfInCacheHandler :: Expr -> Eval Expr -> Eval Expr
}
data Attributes = MkAttributes {
- flat :: !Bool
- orderless :: !Bool
- numericFunction :: !Bool
- holdType :: !(Maybe HoldType)
}
data HoldType
- = HoldFirst
- | HoldRest
- | HoldAll
emptyAttributes :: Attributes
data SymbolRecord = MkSymbolRecord {
- ownValue :: !(Maybe Expr)
- downValues :: !DownValues
- upValues :: !(Seq Rule)
- attributes :: !Attributes
}
data DownValues = MkDownValues {
- sequentialRules :: !(Seq Rule)
- uniqueMatches :: !(Map Expr Expr)
}
newtype Eval a = Eval (ReaderT Context IO a)
runEvalWithContext :: Context -> Eval a -> IO a
runEvalNewContext :: Eval a -> IO a
getContext :: Eval Context
returnIfInCache :: Expr -> Eval Expr -> Eval Expr
addToEvalCache :: Expr -> Eval ()
emitErrorLine :: Text -> Eval ()
emitOutputLine :: Text -> Eval ()
data Decl
- = OwnValue Symbol Expr
- | DownValue Symbol Rule
- | UpValue Symbol Rule
newContext :: IO Context
getLineNumber :: Eval Int
incrLineNumber :: Eval ()
setErrorLineHandler :: Context -> (Text -> IO ()) -> IO ()
setOutputLineHandler :: Context -> (Text -> IO ()) -> IO ()
lookupSymbolRecord :: Symbol -> Eval (Maybe SymbolRecord)
lookupAttributes :: Symbol -> Eval Attributes
addDownValue :: Symbol -> Rule -> Eval ()
addUpValue :: Symbol -> Rule -> Eval ()
addDecl :: Decl -> Eval ()
modifyAttributes :: Symbol -> (Attributes -> Attributes) -> Eval ()
setAttributes :: Symbol -> Attributes -> Eval ()
setFlat :: Attributes -> Attributes
setOrderless :: Attributes -> Attributes
setNumericFunction :: Attributes -> Attributes
setHoldType :: HoldType -> Attributes -> Attributes
clear :: Symbol -> Eval ()
clearAll :: Symbol -> Eval ()
newModuleSymbol :: Symbol -> Eval Symbol
getDefinedSymbols :: Eval [Symbol]
compilePat :: Expr -> Eval Pat
dummyAddToEvalCache :: EvalCache -> Expr -> Eval ()
dummyReturnIfInCache :: EvalCache -> Expr -> Eval Expr -> Eval Expr

Documentation

data Rule #

A rewrite rule used by the evaluator.

Constructors

PatRule Pat Expr	A rule with a compiled pattern and right-hand side expression.
BuiltinRule (Expr -> Eval (Maybe Expr))	A builtin rule implemented by a Haskell function.

Instances

Instances details

Show Rule #
Instance details Defined in Howl.Eval.Context Methods showsPrec :: Int -> Rule -> ShowS # show :: Rule -> String # showList :: [Rule] -> ShowS #
PPrint Rule #
Instance details Defined in Howl.Eval.Context Methods pPrint :: Rule -> String #

data Context #

The mutable state used when evaluating expressions.

Constructors

MkContext
Fields symbolRecordTable :: !(HashTable Symbol SymbolRecord) moduleNumberRef :: !(IORef Int) lineNumberRef :: !(IORef Int) errorLineHandlerRef :: !(IORef (Text -> IO ())) outputLineHandlerRef :: !(IORef (Text -> IO ())) addToEvalCacheHandler :: Expr -> Eval () returnIfInCacheHandler :: Expr -> Eval Expr -> Eval Expr

Instances

Instances details

MonadReader Context Eval #
Instance details Defined in Howl.Eval.Context Methods ask :: Eval Context # local :: (Context -> Context) -> Eval a -> Eval a # reader :: (Context -> a) -> Eval a #

data Attributes #

TODO: Add Protected, NumericFunction, OneIdentity | The attributes associated with a symbol.

Constructors

MkAttributes
Fields flat :: !Bool orderless :: !Bool numericFunction :: !Bool holdType :: !(Maybe HoldType)

Instances

Instances details

Show Attributes #
Instance details Defined in Howl.Eval.Context Methods showsPrec :: Int -> Attributes -> ShowS # show :: Attributes -> String # showList :: [Attributes] -> ShowS #
Eq Attributes #
Instance details Defined in Howl.Eval.Context Methods (==) :: Attributes -> Attributes -> Bool # (/=) :: Attributes -> Attributes -> Bool #
Ord Attributes #
Instance details Defined in Howl.Eval.Context Methods compare :: Attributes -> Attributes -> Ordering # (<) :: Attributes -> Attributes -> Bool # (<=) :: Attributes -> Attributes -> Bool # (>) :: Attributes -> Attributes -> Bool # (>=) :: Attributes -> Attributes -> Bool # max :: Attributes -> Attributes -> Attributes # min :: Attributes -> Attributes -> Attributes #

data HoldType #

The hold behavior of a symbol during evaluation.

Constructors

HoldFirst
HoldRest
HoldAll

Instances

Instances details

Show HoldType #
Instance details Defined in Howl.Eval.Context Methods showsPrec :: Int -> HoldType -> ShowS # show :: HoldType -> String # showList :: [HoldType] -> ShowS #
Eq HoldType #
Instance details Defined in Howl.Eval.Context Methods (==) :: HoldType -> HoldType -> Bool # (/=) :: HoldType -> HoldType -> Bool #
Ord HoldType #
Instance details Defined in Howl.Eval.Context Methods compare :: HoldType -> HoldType -> Ordering # (<) :: HoldType -> HoldType -> Bool # (<=) :: HoldType -> HoldType -> Bool # (>) :: HoldType -> HoldType -> Bool # (>=) :: HoldType -> HoldType -> Bool # max :: HoldType -> HoldType -> HoldType # min :: HoldType -> HoldType -> HoldType #

emptyAttributes :: Attributes #

The default empty set of symbol attributes.

data SymbolRecord #

Information associated with a symbol in the evaluation context.

Constructors

MkSymbolRecord
Fields ownValue :: !(Maybe Expr) downValues :: !DownValues Rules that match expressions where the given symbol is the head upValues :: !(Seq Rule) A rule that matches expressions where the given symbol is 1 level below the head. attributes :: !Attributes

Instances

Instances details

Show SymbolRecord #
Instance details Defined in Howl.Eval.Context Methods showsPrec :: Int -> SymbolRecord -> ShowS # show :: SymbolRecord -> String # showList :: [SymbolRecord] -> ShowS #

data DownValues #

For cases when a pattern matches a unique expression, we store that expression in the uniqueMatches Map for fast lookup. In the evaluator, we try these lookups first before moving through the sequentialRules. | The down-values associated with a symbol.

Constructors

MkDownValues
Fields sequentialRules :: !(Seq Rule) uniqueMatches :: !(Map Expr Expr)

Instances

Instances details

Show DownValues #
Instance details Defined in Howl.Eval.Context Methods showsPrec :: Int -> DownValues -> ShowS # show :: DownValues -> String # showList :: [DownValues] -> ShowS #

newtype Eval a #

The monad in which Howl evaluation runs.

An Eval computation has access to the current evaluation context, including symbol definitions, attributes, line-number state, and output/error handlers.

Constructors

Eval (ReaderT Context IO a)

Instances

Instances details

MonadIO Eval #
Instance details Defined in Howl.Eval.Context Methods liftIO :: IO a -> Eval a #
MonadCatch Eval #
Instance details Defined in Howl.Eval.Context Methods catch :: (HasCallStack, Exception e) => Eval a -> (e -> Eval a) -> Eval a #
MonadMask Eval #
Instance details Defined in Howl.Eval.Context Methods mask :: HasCallStack => ((forall a. Eval a -> Eval a) -> Eval b) -> Eval b # uninterruptibleMask :: HasCallStack => ((forall a. Eval a -> Eval a) -> Eval b) -> Eval b # generalBracket :: HasCallStack => Eval a -> (a -> ExitCase b -> Eval c) -> (a -> Eval b) -> Eval (b, c) #
MonadThrow Eval #
Instance details Defined in Howl.Eval.Context Methods throwM :: (HasCallStack, Exception e) => e -> Eval a #
Applicative Eval #
Instance details Defined in Howl.Eval.Context Methods pure :: a -> Eval a # (<>) :: Eval (a -> b) -> Eval a -> Eval b # liftA2 :: (a -> b -> c) -> Eval a -> Eval b -> Eval c # (>) :: Eval a -> Eval b -> Eval b # (<*) :: Eval a -> Eval b -> Eval a #
Functor Eval #
Instance details Defined in Howl.Eval.Context Methods fmap :: (a -> b) -> Eval a -> Eval b # (<$) :: a -> Eval b -> Eval a #
Monad Eval #
Instance details Defined in Howl.Eval.Context Methods (>>=) :: Eval a -> (a -> Eval b) -> Eval b # (>>) :: Eval a -> Eval b -> Eval b # return :: a -> Eval a #
MonadFail Eval #
Instance details Defined in Howl.Eval.Context Methods fail :: String -> Eval a #
MonadReader Context Eval #
Instance details Defined in Howl.Eval.Context Methods ask :: Eval Context # local :: (Context -> Context) -> Eval a -> Eval a # reader :: (Context -> a) -> Eval a #
ToExpr a => ToBuiltin (Eval (Maybe a)) #	A monadic builtin that may fail to match its arguments, signified by `Nothing`.
Instance details Defined in Howl.Builtins.ToBuiltin Methods toBuiltin :: Eval (Maybe a) -> Seq Expr -> Eval (Maybe Expr) #
ToExpr a => ToBuiltin (Eval a) #	A monadic builtin that always matches its arguments.
Instance details Defined in Howl.Builtins.ToBuiltin Methods toBuiltin :: Eval a -> Seq Expr -> Eval (Maybe Expr) #
(FromExpr a, ToExpr b) => ToBuiltin (Variadic a (Eval (Maybe b))) #	A variadic monadic builtin that may fail to match its arguments, signified by `Nothing`.
Instance details Defined in Howl.Builtins.ToBuiltin Methods toBuiltin :: Variadic a (Eval (Maybe b)) -> Seq Expr -> Eval (Maybe Expr) #
(FromExpr a, ToExpr b) => ToBuiltin (Variadic a (Eval b)) #	A variadic monadic builtin that always matches its arguments.
Instance details Defined in Howl.Builtins.ToBuiltin Methods toBuiltin :: Variadic a (Eval b) -> Seq Expr -> Eval (Maybe Expr) #

runEvalWithContext :: Context -> Eval a -> IO a #

Run an Eval computation in the given context.

runEvalNewContext :: Eval a -> IO a #

Create a new context and run an Eval computation in it.

getContext :: Eval Context #

Get the current context.

returnIfInCache :: Expr -> Eval Expr -> Eval Expr #

Return the cached value of an expression when available, otherwise run the given computation.

addToEvalCache :: Expr -> Eval () #

Add an expression to the evaluation cache.

emitErrorLine :: Text -> Eval () #

Emit a line of error output using the current error handler.

emitOutputLine :: Text -> Eval () #

Emit a line of standard output using the current output handler.

data Decl #

A declaration that can be added to the evaluation context.

Constructors

OwnValue Symbol Expr	An own-value assignment for a symbol.
DownValue Symbol Rule	A down-value rule for expressions with the given head.
UpValue Symbol Rule	An up-value rule for expressions containing the given symbol.

Instances

Instances details

Show Decl #
Instance details Defined in Howl.Eval.Context Methods showsPrec :: Int -> Decl -> ShowS # show :: Decl -> String # showList :: [Decl] -> ShowS #