Text.Earley.Internal

This module exposes the internals of the package: its API may change independently of the PVP-compliant version number.

Concrete rules and productions

data Rule s r e t a

The concrete rule type that the parser uses

Constructors

Rule

Fields

ruleProd :: ProdR s r e t a

ruleConts :: !(STRef s (STRef s [Cont s r e t a r]))

ruleNulls :: !(Results s a)

mkRule :: ProdR s r e t a -> ST s (Rule s r e t a)

prodNulls :: ProdR s r e t a -> Results s a

removeNulls :: ProdR s r e t a -> ProdR s r e t a

Remove (some) nulls from a production

type ProdR s r e t a = Prod (Rule s r) e t a

resetConts :: Rule s r e t a -> ST s ()

Delayed results

newtype Results s a

Constructors

Results

Fields

unResults :: ST s [a]

Instances

Monad (Results s)

Functor (Results s)

Applicative (Results s)

Alternative (Results s)

Monoid (Results s a)

lazyResults :: ST s [a] -> ST s (Results s a)

States and continuations

data BirthPos

Constructors

Previous

Current

Instances

Eq BirthPos

data State s r e t a where

An Earley state with result type a.

Constructors

State :: !(ProdR s r e t a) -> !(a -> Results s b) -> !BirthPos -> !(Conts s r e t b c) -> State s r e t c

Final :: !(Results s a) -> State s r e t a

data Cont s r e t a b where

A continuation accepting an a and producing a b.

Constructors

Cont :: !(a -> Results s b) -> !(ProdR s r e t (b -> c)) -> !(c -> Results s d) -> !(Conts s r e t d e') -> Cont s r e t a e'

FinalCont :: (a -> Results s c) -> Cont s r e t a c

data Conts s r e t a c

Constructors

Conts

Fields

conts :: !(STRef s [Cont s r e t a c])

contsArgs :: !(STRef s (Maybe (STRef s (Results s a))))

newConts :: STRef s [Cont s r e t a c] -> ST s (Conts s r e t a c)

contraMapCont :: (b -> Results s a) -> Cont s r e t a c -> Cont s r e t b c

contToState :: BirthPos -> Results s a -> Cont s r e t a c -> State s r e t c

simplifyCont :: Conts s r e t b a -> ST s [Cont s r e t b a]

Strings of non-ambiguous continuations can be optimised by removing indirections.

Grammars

initialState :: ProdR s a e t a -> ST s (State s a e t a)

Given a grammar, construct an initial state.

Parsing

data Report e i

A parsing report, which contains fields that are useful for presenting errors to the user if a parse is deemed a failure. Note however that we get a report even when we successfully parse something.

Constructors

Report

Fields

position :: Int

The final position in the input (0-based) that the parser reached.

expected :: [e]

The named productions processed at the final position.

unconsumed :: i

The part of the input string that was not consumed, which may be empty.

Instances

(Eq e, Eq i) => Eq (Report e i)

(Ord e, Ord i) => Ord (Report e i)

(Read e, Read i) => Read (Report e i)

(Show e, Show i) => Show (Report e i)

data Result s e i a

The result of a parse.

Constructors

Ended (Report e i)

The parser ended.

Parsed (ST s [a]) Int i (ST s (Result s e i a))

The parser parsed a number of as. These are given as a computation, ST s [a] that constructs the as when run. We can thus save some work by ignoring this computation if we do not care about the results. The Int is the position in the input where these results were obtained, the i the rest of the input, and the last component is the continuation.

Instances

Functor (Result s e i)

safeHead :: ListLike i t => i -> Maybe t

data ParseEnv s e i t a

Constructors

ParseEnv

Fields

results :: ![ST s [a]]

Results ready to be reported (when this position has been processed)

next :: ![State s a e t a]

States to process at the next position

reset :: !(ST s ())

Computation that resets the continuation refs of productions

names :: ![e]

Named productions encountered at this position

curPos :: !Int

The current position in the input string

input :: !i

The input string

emptyParseEnv :: i -> ParseEnv s e i t a

parse

Arguments

:: ListLike i t

=> [State s a e t a]

States to process at this position

-> ParseEnv s e i t a

-> ST s (Result s e i a)

The internal parsing routine

parser :: ListLike i t => (forall r. Grammar r (Prod r e t a)) -> ST s (i -> ST s (Result s e i a))

Create a parser from the given grammar.

allParses :: (forall s. ST s (i -> ST s (Result s e i a))) -> i -> ([(a, Int)], Report e i)

Return all parses from the result of a given parser. The result may contain partial parses. The Ints are the position at which a result was produced.

fullParses :: ListLike i t => (forall s. ST s (i -> ST s (Result s e i a))) -> i -> ([a], Report e i)

Return all parses that reached the end of the input from the result of a given parser.

report :: ListLike i t => (forall s. ST s (i -> ST s (Result s e i a))) -> i -> Report e i

See e.g. how far the parser is able to parse the input string before it fails. This can be much faster than getting the parse results for highly ambiguous grammars.