PGF2

This module is an Application Programming Interface to load and interpret grammars compiled in the Portable Grammar Format (PGF). The PGF format is produced as the final output from the GF compiler. The API is meant to be used for embedding GF grammars in Haskell programs

PGF

data PGF

An abstract data type representing multilingual grammar in Portable Grammar Format.

readPGF :: FilePath -> IO PGF

Reads file in Portable Grammar Format and produces PGF structure. The file is usually produced with:

$ gf -make <grammar file name>

showPGF :: PGF -> String

Identifiers

type CId = String

An data type that represents identifiers for functions and categories in PGF.

Abstract syntax

type AbsName

Arguments

 = CId

Name of abstract syntax

abstractName :: PGF -> AbsName

The abstract language name is the name of the top-level abstract module

Categories

type Cat

Arguments

 = CId

Name of syntactic category

categories :: PGF -> [Cat]

List of all categories defined in the grammar. The categories are defined in the abstract syntax with the 'cat' keyword.

categoryContext :: PGF -> Cat -> [Hypo]

Functions

type Fun

Arguments

 = CId

Name of function

functions :: PGF -> [Fun]

List of all functions defined in the abstract syntax

functionsByCat :: PGF -> Cat -> [Fun]

List of all functions defined for a category

functionType :: PGF -> Fun -> Maybe Type

The type of a function

functionIsConstructor :: PGF -> Fun -> Bool

The type of a function

hasLinearization :: Concr -> Fun -> Bool

Returns True if there is a linearization defined for that function in that language

Expressions

data Expr

Instances

Eq Expr

Defined in PGF2.Expr

Methods

(==) :: Expr -> Expr -> Bool

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

Data Expr

Defined in PGF2.Expr

Methods

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

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

toConstr :: Expr -> Constr

dataTypeOf :: Expr -> DataType

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

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

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

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

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

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

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

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

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

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

Show Expr

Defined in PGF2.Expr

Methods

showsPrec :: Int -> Expr -> ShowS

show :: Expr -> String

showList :: [Expr] -> ShowS

showExpr :: [CId] -> Expr -> String

renders an expression as a String. The list of identifiers is the list of all free variables in the expression in order reverse to the order of binding.

readExpr :: String -> Maybe Expr

parses a String as an expression

pExpr :: ReadS Expr

mkAbs :: BindType -> CId -> Expr -> Expr

Constructs an expression by lambda abstraction

unAbs :: Expr -> Maybe (BindType, CId, Expr)

Decomposes an expression into an abstraction and a body

mkApp :: Fun -> [Expr] -> Expr

Constructs an expression by applying a function to a list of expressions

unApp :: Expr -> Maybe (Fun, [Expr])

Decomposes an expression into an application of a function

mkStr :: String -> Expr

Constructs an expression from a string literal

unStr :: Expr -> Maybe String

Decomposes an expression into a string literal

mkInt :: Int -> Expr

Constructs an expression from an integer literal

unInt :: Expr -> Maybe Int

Decomposes an expression into an integer literal

mkFloat :: Double -> Expr

Constructs an expression from a real number

unFloat :: Expr -> Maybe Double

Decomposes an expression into a real number literal

mkMeta :: Int -> Expr

Constructs a meta variable as an expression

unMeta :: Expr -> Maybe Int

Decomposes an expression into a meta variable

mkCId :: p -> p

this functions is only for backward compatibility with the old Haskell runtime

exprHash :: Int32 -> Expr -> Int32

exprSize :: Expr -> Int

exprFunctions :: Expr -> [Fun]

exprSubstitute :: Expr -> [Expr] -> Expr

treeProbability :: PGF -> Expr -> Float

Types

data Type

Instances

Show Type

Defined in PGF2.Type

Methods

showsPrec :: Int -> Type -> ShowS

show :: Type -> String

showList :: [Type] -> ShowS

type Hypo = (BindType, CId, Type)

Hypo represents a hypothesis in a type i.e. in the type A -> B, A is the hypothesis

data BindType

Constructors

Explicit

Implicit

Instances

Show BindType

Defined in PGF2.Expr

Methods

showsPrec :: Int -> BindType -> ShowS

show :: BindType -> String

showList :: [BindType] -> ShowS

startCat :: PGF -> Type

The start category is defined in the grammar with the 'startcat' flag. This is usually the sentence category but it is not necessary. Despite that there is a start category defined you can parse with any category. The start category definition is just for convenience.

readType :: String -> Maybe Type

parses a String as a type

showType :: [CId] -> Type -> String

renders a type as a String. The list of identifiers is the list of all free variables in the type in order reverse to the order of binding.

showContext :: [CId] -> [Hypo] -> String

renders a type as a String. The list of identifiers is the list of all free variables in the type in order reverse to the order of binding.

mkType :: [Hypo] -> CId -> [Expr] -> Type

creates a type from a list of hypothesises, a category and a list of arguments for the category. The operation mkType [h_1,...,h_n] C [e_1,...,e_m] will create h_1 -> ... -> h_n -> C e_1 ... e_m

unType :: Type -> ([Hypo], CId, [Expr])

Decomposes a type into a list of hypothesises, a category and a list of arguments for the category.

Type checking

Dynamically-built expressions should always be type-checked before using in other functions, as the exceptions thrown by using invalid expressions may not catchable.

checkExpr :: PGF -> Expr -> Type -> Either String Expr

Checks an expression against a specified type.

inferExpr :: PGF -> Expr -> Either String (Expr, Type)

Tries to infer the type of an expression. Note that even if the expression is type correct it is not always possible to infer its type in the GF type system. In this case the function returns an error.

checkType :: PGF -> Type -> Either String Type

Check whether a type is consistent with the abstract syntax of the grammar.

Computing

compute :: PGF -> Expr -> Expr

Concrete syntax

type ConcName

Arguments

 = CId

Name of concrete syntax

data Concr

languages :: PGF -> Map ConcName Concr

List of all languages available in the grammar.

concreteName :: Concr -> ConcName

languageCode :: Concr -> String

Linearization

linearize :: Concr -> Expr -> String

Linearizes an expression as a string in the language

linearizeAll :: Concr -> Expr -> [String]

Generates all possible linearizations of an expression

tabularLinearize :: Concr -> Expr -> [(String, String)]

Generates a table of linearizations for an expression

tabularLinearizeAll :: Concr -> Expr -> [[(String, String)]]

Generates a table of linearizations for an expression

bracketedLinearize :: Concr -> Expr -> [BracketedString]

bracketedLinearizeAll :: Concr -> Expr -> [[BracketedString]]

type FId = Int

data BracketedString

BracketedString represents a sentence that is linearized as usual but we also want to retain the 'brackets' that mark the beginning and the end of each constituent.

Constructors

Leaf String

this is the leaf i.e. a single token

BIND

the surrounding tokens must be bound together

Bracket CId !FId String CId [BracketedString]

this is a bracket. The CId is the category of the phrase. The FId is an unique identifier for every phrase in the sentence. For context-free grammars i.e. without discontinuous constituents this identifier is also unique for every bracket. When there are discontinuous phrases then the identifiers are unique for every phrase but not for every bracket since the bracket represents a constituent. The different constituents could still be distinguished by using the analysis string. If the grammar is reduplicating then the constituent indices will be the same for all brackets that represents the same constituent. The second CId is the name of the abstract function that generated this phrase.

showBracketedString :: BracketedString -> String

Renders the bracketed string as a string where the brackets are shown as (S ...) where S is the category.

flattenBracketedString :: BracketedString -> [String]

Extracts the sequence of tokens from the bracketed string

printName :: Concr -> Fun -> Maybe String

categoryFields :: Concr -> Cat -> Maybe [String]

alignWords :: Concr -> Expr -> [(String, [Int])]

Parsing

data ParseOutput a

This data type encodes the different outcomes which you could get from the parser.

Constructors

ParseFailed Int String

The integer is the position in number of unicode characters where the parser failed. The string is the token where the parser have failed.

ParseOk a

If the parsing and the type checking are successful we get the abstract syntax trees as either a list or a chart.

ParseIncomplete

The sentence is not complete.

parse :: Concr -> Type -> String -> ParseOutput [(Expr, Float)]

parseWithHeuristics

Arguments

:: Concr

the language with which we parse

-> Type

the start category

-> String

the input sentence

-> Double

the heuristic factor. A negative value tells the parser to lookup up the default from the grammar flags

-> [(Cat, String -> Int -> Maybe (Expr, Float, Int))]

a list of callbacks for literal categories. The arguments of the callback are: the index of the constituent for the literal category; the input sentence; the current offset in the sentence. If a literal has been recognized then the output should be Just (expr,probability,end_offset)

-> ParseOutput [(Expr, Float)]

parseToChart

Arguments

:: Concr

the language with which we parse

-> Type

the start category

-> String

the input sentence

-> Double

the heuristic factor. A negative value tells the parser to lookup up the default from the grammar flags

-> [(Cat, String -> Int -> Maybe (Expr, Float, Int))]

a list of callbacks for literal categories. The arguments of the callback are: the index of the constituent for the literal category; the input sentence; the current offset in the sentence. If a literal has been recognized then the output should be Just (expr,probability,end_offset)

-> Int

the maximal number of roots

-> ParseOutput ([FId], Map FId ([(Int, Int, String)], [(Expr, [PArg], Float)], Cat))

data PArg

Constructors

PArg [FId] !FId

Instances

Eq PArg

Defined in PGF2.FFI

Methods

(==) :: PArg -> PArg -> Bool

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

Ord PArg

Defined in PGF2.FFI

Methods

compare :: PArg -> PArg -> Ordering

(<) :: PArg -> PArg -> Bool

(<=) :: PArg -> PArg -> Bool

(>) :: PArg -> PArg -> Bool

(>=) :: PArg -> PArg -> Bool

max :: PArg -> PArg -> PArg

min :: PArg -> PArg -> PArg

Show PArg

Defined in PGF2.FFI

Methods

showsPrec :: Int -> PArg -> ShowS

show :: PArg -> String

showList :: [PArg] -> ShowS

complete

Arguments

:: Concr

the language with which we parse

-> Type

the start category

-> String

the input sentence (excluding token being completed)

-> String

prefix (partial token being completed)

-> ParseOutput [(String, CId, CId, Float)]

(token, category, function, probability)

Returns possible completions of the current partial input.

Sentence Lookup

lookupSentence

Arguments

:: Concr

the language with which we parse

-> Type

the start category

-> String

the input sentence

-> [(Expr, Float)]

Generation

generateAll :: PGF -> Type -> [(Expr, Float)]

Generates an exhaustive possibly infinite list of all abstract syntax expressions of the given type. The expressions are ordered by their probability.

Morphological Analysis

type MorphoAnalysis = (Fun, String, Float)

This triple is returned by all functions that deal with the grammar's lexicon. Its first element is the name of an abstract lexical function which can produce a given word or a multiword expression (i.e. this is the lemma). After that follows a string which describes the particular inflection form.

The last element is a logarithm from the the probability of the function. The probability is not conditionalized on the category of the function. This makes it possible to compare the likelihood of two functions even if they have different types.

lookupMorpho :: Concr -> String -> [MorphoAnalysis]

lookupMorpho takes a string which must be a single word or a multiword expression. It then computes the list of all possible morphological analyses.

lookupCohorts :: Concr -> String -> [(Int, String, [MorphoAnalysis], Int)]

lookupCohorts takes an arbitrary string an produces a list of all places where lexical items from the grammar have been identified (i.e. cohorts). The list consists of triples of the format (start,ans,end), where start-end identifies the span in the text and ans is the list of possible morphological analyses similar to lookupMorpho.

The list is sorted first by the start position and after than by the end position. This can be used for instance if you want to filter only the longest matches.

fullFormLexicon :: Concr -> [(String, [MorphoAnalysis])]

filterBest :: [(Int, String, [MorphoAnalysis], Int)] -> [(Int, String, [MorphoAnalysis], Int)]

filterLongest :: [(Int, String, [MorphoAnalysis], Int)] -> [(Int, String, [MorphoAnalysis], Int)]

Visualizations

data GraphvizOptions

Constructors

GraphvizOptions

Fields

• noLeaves :: Bool
• noFun :: Bool
• noCat :: Bool
• noDep :: Bool
• nodeFont :: String
• leafFont :: String
• nodeColor :: String
• leafColor :: String
• nodeEdgeStyle :: String
• leafEdgeStyle :: String

graphvizDefaults :: GraphvizOptions

graphvizAbstractTree :: PGF -> GraphvizOptions -> Expr -> String

Renders an abstract syntax tree in a Graphviz format.

graphvizParseTree :: Concr -> GraphvizOptions -> Expr -> String

graphvizWordAlignment :: [Concr] -> GraphvizOptions -> Expr -> String

Exceptions

newtype PGFError

Constructors

PGFError String

Instances

Show PGFError

Defined in PGF2

Methods

showsPrec :: Int -> PGFError -> ShowS

show :: PGFError -> String

showList :: [PGFError] -> ShowS

Exception PGFError

Defined in PGF2

Methods

toException :: PGFError -> SomeException

fromException :: SomeException -> Maybe PGFError

displayException :: PGFError -> String

Grammar specific callbacks

type LiteralCallback = PGF -> (ConcName, Concr) -> String -> String -> Int -> Maybe (Expr, Float, Int)

literalCallbacks :: [(AbsName, [(Cat, LiteralCallback)])]

Callbacks for the App grammar