Safe Haskell	None
Language	Haskell2010

GLL.Combinators.Interface

Contents

Elementary parsers
- Elementary parsers using the Token datatype
- Elementary character-level parsers
Elementary combinators
Types
- Grammar (combinator expression) types
- Parseable token types
Running a parser
Derived combinators
Lifting
Memoisation

Description

This module provides a combinator library in which combinators act as an interface to a back-end parser. This technique is inspired by Tom Ridge (2014) and Peter Ljunglöf (2002). The back-end parser is provided in GLL.Parser. The library is fully general: it enables writing parsers for arbitrary context-free grammars.

The user writes a combinator expression representing a grammar. The represented grammar is extracted and given, together with an input string, to a back-end parser. The derivations constructed by the parser act as a guide in the "semantic phase" in which the combinator expressions are evaluated to produce semantic results for all derivations. Infinitely many derivations would result in a loop. This problem is avoided by discarding the derivations that would arise from such a loop.

This library uses GLL.Parser as the back-end parser and provides Control.Applicative-like parser combinators: <**> for sequencing, <||> for choice, <$$> for application, satisfy instead of pure and derived combinators <**, **>, <$$, many, some and optional.

The semantic phase might benefit from memoisation (see memo). Using memoisation voids pureness waranty".

Example usage

This library differs from parser combinator libraries in that combinator expressions are used to describe a grammar rather than a parser.

A rule is considered to be of the form X ::= a | .. | z, and represented by the combinator expression.

pX = "X" <::=> altA <||> ... <||> altZ

Alternates ('a' ... 'z') start with the application of a semantic action using <$$> (or variants <$$ and satisfy). The alternate is extended with <**> (or variants **>, <**).

altA = action1 <$$> keychar 'a' <**> pX
altZ = action2 <$$> keychar 'z'

Usability is improved by automatic lifting between expressions that represent symbols and alternates. The main difference with Control.Applicative style parser combinator libraries is that the user must use <:=> (or <::=>) to represent all recursive nonterminals and must use <::=> to represent all nonterminals that potentially lead to an infinite number of derivations. It is, however, possible to represent left-recursive nonterminals.

Example

In this example we define expressions for parsing (and evaluating) simple arithmetic expressions for single digit integers.

The library is capable of parsing arbitrary token types that are Parseable, orderable and have a Show instance. This example demonstrates the usage of the builtin Token datatype and uses the elementary parsers keychar and int_lit to create parsers for character- and integer-terminals.

We define a very simpler lexer first.

lexer :: String -> [Token]
lexer [] = []
lexer (x:xs)
    | isDigit x = IntLit (Just (read [x])) : lexer xs
    | otherwise = Token x                   : lexer xs

Note that the Char constructor of the Token type is used for character-level parsing. Char contains no lexeme, unlike the Int constructor.

Consider the following (highly ambiguous and left-recursive) grammar:

Expr ::= Expr '-' Expr
       | Expr '+' Expr
       | Expr '*' Expr
       | Expr '/' Expr
       | INT
       | '(' Expr ')'

The grammar is translated to the following combinator expression, adding the expected evaluation functions as semantic actions.

pExpr :: BNF Token Int
pExpr = "Expr" <::=> (-) <$$> pExpr <** keychar '-' <**> pExpr
                 <||> (+) <$$> pExpr <** keychar '+' <**> pExpr
                 <||> (*) <$$> pExpr <** keychar '*' <**> pExpr
                 <||> div <$$> pExpr <** keychar '/' <**> pExpr
                 <||> int_lit
                 <||> parens pExpr

Note that <** is used to ignore the parse result of the second argument and that **> is used to ignore the parse result of the first argument. These combinators help us to define the derived combinators within and parens.

within :: BNF Token a -> BNF Token b -> BNF Token a -> BNF Token b
within l p r = mkRule $ l **> p <** r

parens :: BNF Token a -> BNF Token a
parens p = within (keychar '(') p (keychar ')')

All possible evaluations are obtained by invoking the parse function.

run1 = parse pExpr (lexer "1+2*2-5")            -- [0,1,0,-5,-9] 
run2 = parse pExpr (lexer "((1+(2*2))-3)-5")    -- [-3]

With every introduction of an operator +, -, * or / the number of ambiguities is multiplied. The number of ambiguities behaves like the sequence https://oeis.org/A000108.

Simple disambiguation

This library offers simple disambiguation strategies that are applied post-parse (the parser still faces the ambiguity, but the semantic evaluation only yields the results according to the strategy). The disambiguations strategies are still in the experimental phase.

We group the operators according to their priorities and use <::= to turn the choice operator <||> into a left-biased operator locally (use leftBiased for the same effect globally).

pExpr1 :: BNF Token Int
pExpr1 = "Expr" <::=  (      (-) <$$> pExpr1 <** keychar '-' <**> pExpr1
                        <||> (+) <$$> pExpr1 <** keychar '+' <**> pExpr1 )
                 <||> (      (*) <$$> pExpr1 <** keychar '*' <**> pExpr1
                        <||> div <$$> pExpr1 <** keychar '/' <**> pExpr1 )
                 <||> (      int_lit
                        <||> parens pExpr1 )

run3 = parseWithOptions [maximumPivotAtNt] pExpr1 (lexer "1+2*2-5") -- [0]

The option maximumPivotAtNt enables the 'longest-match' disambiguation strategy and makes the arithmetic operators left-associative.

Grammar rewrites

To deal with the particular ambiguities associated with operators we can rewrite the grammar to disambiguate pre-parse.

We define the chainl combinator for parsing chains of left-associative operators.

chainl :: BNF Token a -> BNF Token (a -> a -> a) -> BNF Token a
chainl p s = mkRule $
    foldl (flip ($)) <$$> p <**> many (flip <$$> s <**> p)

The expression parser is written with chainl as follows:

pExpr2 :: BNF Token Int
pExpr2 = pE1
 where  pE1 = chainl pE2 ("E1" <::=> (+) <$$ keychar '+' <||> (-) <$$ keychar '-')
        pE2 = chainl pE3 ("E2" <::=> (*) <$$ keychar '*' <||> div <$$ keychar '/')
        pE3 = "E3" <::=> int_lit <||> parens pExpr2

run4 = parse pExpr2 (lexer "1+2*2-5")       -- [0]

Pre-parse disambiguation is desirable, as the parsing process could speed up dramatically. In general however, it is not always possible to find the appropriate grammar rewrite and implement it in a high-level combinator such as chainl, motivating the existence of this library.

More simple examples can be found in GLL.Combinators.Test.Interface.

Synopsis

term_parser :: t -> (t -> a) -> SymbExpr t a
satisfy :: (Show t, Ord t) => a -> AltExpr t a
keychar :: SubsumesToken t => Char -> SymbExpr t Char
keyword :: SubsumesToken t => String -> SymbExpr t String
int_lit :: SubsumesToken t => SymbExpr t Int
float_lit :: SubsumesToken t => SymbExpr t Double
bool_lit :: SubsumesToken t => SymbExpr t Bool
char_lit :: SubsumesToken t => SymbExpr t Char
string_lit :: SubsumesToken t => SymbExpr t String
alt_id_lit :: SubsumesToken t => SymbExpr t String
id_lit :: SubsumesToken t => SymbExpr t String
token :: SubsumesToken t => String -> SymbExpr t String
char :: Char -> SymbExpr Char Char
(<**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t (a -> b) -> s t a -> AltExpr t b
(<||>) :: (Show t, Ord t, IsAltExpr i, HasAlts b) => i t a -> b t a -> AltExprs t a
(<$$>) :: (Show t, Ord t, IsSymbExpr s) => (a -> b) -> s t a -> AltExpr t b
(<:=>) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a
(<::=>) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a
chooses :: (Show t, Ord t, IsAltExpr alt) => String -> [alt t a] -> SymbExpr t a
chooses_prec :: (Show t, Ord t, IsAltExpr alt) => String -> [alt t a] -> SymbExpr t a
type BNF t a = SymbExpr t a
data SymbExpr t a
data AltExpr t a
type AltExprs = OO [] AltExpr
data Token
- = Char Char
- | Keyword String
- | EOS
- | Epsilon
- | IntLit (Maybe Int)
- | FloatLit (Maybe Double)
- | BoolLit (Maybe Bool)
- | StringLit (Maybe String)
- | CharLit (Maybe Char)
- | IDLit (Maybe String)
- | AltIDLit (Maybe String)
- | Token String (Maybe String)
class (Ord a, Eq a, Show a) => Parseable a where
- eos :: a
- eps :: a
- matches :: a -> a -> Bool
- unlex :: a -> String
class SubsumesToken a where
- upcast :: Token -> a
- downcast :: a -> Maybe Token
unlexTokens :: [Token] -> String
unlexToken :: Token -> String
grammarOf :: (Show t, Parseable t, IsSymbExpr s) => s t a -> Grammar t
parse :: (Show t, Parseable t, IsSymbExpr s) => s t a -> [t] -> [a]
printParseData :: (Parseable t, IsSymbExpr s, Show a) => s t a -> [t] -> IO ()
evaluatorWithParseData :: (Parseable t, IsSymbExpr s, Show a) => s t a -> [t] -> [a]
parseWithOptions :: (Show t, Parseable t, IsSymbExpr s) => CombinatorOptions -> s t a -> [t] -> [a]
parseWithParseOptions :: (Show t, Parseable t, IsSymbExpr s) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> [a]
printParseDataWithOptions :: (Parseable t, IsSymbExpr s, Show a) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> IO ()
evaluatorWithParseDataAndOptions :: (Parseable t, IsSymbExpr s, Show a) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> [a]
printGrammarData :: (Show t, Parseable t, IsSymbExpr s) => s t a -> IO ()
type CombinatorOptions = [CombinatorOption]
type CombinatorOption = PCOptions -> PCOptions
maximumErrors :: Int -> CombinatorOption
throwErrors :: CombinatorOption
maximumPivot :: CombinatorOption
maximumPivotAtNt :: CombinatorOption
leftBiased :: CombinatorOption
fullSPPF :: ParseOption
allNodes :: ParseOption
packedNodesOnly :: ParseOption
strictBinarisation :: ParseOption
noSelectTest :: ParseOption
parseWithOptionsAndError :: (Show t, Parseable t, IsSymbExpr s) => CombinatorOptions -> s t a -> [t] -> Either String [a]
parseWithParseOptionsAndError :: (Show t, Parseable t, IsSymbExpr s) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> Either String [a]
parseResult :: (Show t, Parseable t, IsSymbExpr s) => s t a -> [t] -> ParseResult t
parseResultWithOptions :: (Show t, Parseable t, IsSymbExpr s) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> ParseResult t
data ParseResult t = ParseResult {
- sppf_result :: SPPF t
- res_success :: Bool
- res_successes :: Int
- nr_descriptors :: Int
- nr_nterm_nodes :: Int
- nr_term_nodes :: Int
- nr_intermediate_nodes :: Int
- nr_packed_nodes :: Int
- nr_packed_node_attempts :: Int
- nr_sppf_edges :: Int
- nr_gss_nodes :: Int
- nr_gss_edges :: Int
- error_message :: String
}
default_lexer :: SubsumesToken t => String -> [t]
lexer :: SubsumesToken t => LexerSettings -> String -> [t]
lexerEither :: SubsumesToken t => LexerSettings -> String -> Either String [t]
data LexerSettings = LexerSettings {
- keychars :: [Char]
- keywords :: [String]
- whitespace :: Char -> Bool
- lineComment :: String
- blockCommentOpen :: String
- blockCommentClose :: String
- identifiers :: RE Char String
- altIdentifiers :: RE Char String
- tokens :: [(String, RE Char String)]
- signed_int_lits :: Bool
}
emptyLanguage :: LexerSettings
mkNt :: (Show t, Ord t, IsSymbExpr s) => s t a -> String -> String
(<$$) :: (Show t, Ord t, IsSymbExpr s) => b -> s t a -> AltExpr t b
(**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t b
(<**) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t a
optional :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t (Maybe a)
preferably :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t (Maybe a)
reluctantly :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t (Maybe a)
optionalWithDef :: (Show t, Ord t, IsSymbExpr s) => s t a -> a -> SymbExpr t a
multiple :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a]
multiple1 :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a]
multipleSepBy :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a]
multipleSepBy1 :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a]
multipleSepBy2 :: (Show t, Ord t, IsSymbExpr s2, IsSymbExpr s, IsAltExpr s2) => s t a -> s2 t b -> BNF t [a]
within :: (Show t, Ord t, IsSymbExpr s) => BNF t a -> s t b -> BNF t c -> BNF t b
parens :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b
braces :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b
brackets :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b
angles :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b
foldr_multiple :: (IsSymbExpr s, Parseable t) => s t (a -> a) -> a -> BNF t a
foldr_multipleSepBy :: (IsSymbExpr s, Parseable t) => s t (a -> a) -> s t b -> a -> BNF t a
fromOpTable :: (SubsumesToken t, Parseable t, IsSymbExpr s) => String -> OpTable e -> s t e -> BNF t e
opTableFromList :: [(Double, [(String, Fixity e)])] -> OpTable e
type OpTable e = Map Double [(String, Fixity e)]
data Assoc
- = LAssoc
- | RAssoc
- | NA
data Fixity e
- = Prefix (String -> e -> e)
- | Infix (e -> String -> e -> e) Assoc
(<:=) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a
(<::=) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a
(<<<**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t (a -> b) -> s t a -> AltExpr t b
(<**>>>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t (a -> b) -> s t a -> AltExpr t b
(<<**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t b
(<<<**) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t a
(**>>>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t b
(<**>>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t a
longest_match :: (Show t, Ord t, IsAltExpr alt) => alt t a -> AltExpr t a
shortest_match :: (Show t, Ord t, IsAltExpr alt) => alt t a -> AltExpr t a
many :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a]
many1 :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a]
some :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a]
some1 :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a]
manySepBy :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a]
manySepBy1 :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a]
manySepBy2 :: (Show t, Ord t, IsSymbExpr s2, IsSymbExpr s, IsAltExpr s2) => s t a -> s2 t b -> BNF t [a]
someSepBy :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a]
someSepBy1 :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a]
someSepBy2 :: (Show t, Ord t, IsSymbExpr s2, IsSymbExpr s, IsAltExpr s2) => s t a -> s2 t b -> BNF t [a]
class HasAlts a where
- altsOf :: (Show t, Ord t) => a t b -> [AltExpr t b]
class IsSymbExpr a where
- toSymb :: (Show t, Ord t) => a t b -> SymbExpr t b
- mkRule :: (Show t, Ord t) => a t b -> BNF t b
class IsAltExpr a where
- toAlt :: (Show t, Ord t) => a t b -> AltExpr t b
memo :: (Ord t, Show t, IsSymbExpr s) => MemoRef [a] -> s t a -> SymbExpr t a
newMemoTable :: MemoRef a
memClear :: MemoRef a -> IO ()
type MemoTable a = IntMap (IntMap a)
type MemoRef a = IORef (MemoTable a)
useMemoisation :: CombinatorOption

Elementary parsers

term_parser :: t -> (t -> a) -> SymbExpr t a Source #

Create a symbol-parse for a terminal given:

The Parseable token represented by the terminal.
A function from that Parseable to a semantic result.

satisfy :: (Show t, Ord t) => a -> AltExpr t a Source #

The empty right-hand side that yields its first argument as a semantic result.

Elementary parsers using the `Token` datatype

keychar :: SubsumesToken t => Char -> SymbExpr t Char Source #

Parse a single character, using a SubsumesToken type.

keyword :: SubsumesToken t => String -> SymbExpr t String Source #

Parse a single character, using a SubsumesToken type.

int_lit :: SubsumesToken t => SymbExpr t Int Source #

Parse a single integer, using a SubsumesToken type. Returns the lexeme interpreted as an Int.

float_lit :: SubsumesToken t => SymbExpr t Double Source #

Parse a single floating point literal, using a SubsumesToken type. Returns the lexeme interpreted as a Double.

bool_lit :: SubsumesToken t => SymbExpr t Bool Source #

Parse a single Boolean, using a SubsumesToken type. Returns the lexeme interpreter as a Boolean.

char_lit :: SubsumesToken t => SymbExpr t Char Source #

Parse a single Character literal, using a SubsumesToken type. Returns the lexeme interpreted as a Character literal.

string_lit :: SubsumesToken t => SymbExpr t String Source #

Parse a single String literal, using a SubsumesToken type. Returns the lexeme interpreted as a String literal.

alt_id_lit :: SubsumesToken t => SymbExpr t String Source #

Parse a single alternative identifier, using a SubsumesToken type. Returns the lexeme as a String.

id_lit :: SubsumesToken t => SymbExpr t String Source #

Parse a single identifier, using a SubsumesToken type. Returns the lexeme as a String.

token :: SubsumesToken t => String -> SymbExpr t String Source #

Parse a single arbitrary token, using a SubsumesToken type. Returns the lexeme.

Elementary character-level parsers

char :: Char -> SymbExpr Char Char Source #

Parse a single character.

char c = term_parser c id

Currently, this is the only character-level combinator exported by this module. Please use token-level combinators for practical parsing. Might change in the future.

Elementary combinators

Sequencing

(<**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t (a -> b) -> s t a -> AltExpr t b infixl 4 Source #

Add a SymbExpr to the right-hand side represented by an AltExpr creating a new AltExpr. The semantic result of the first argument is applied to the second as a cross-product.

Choice

(<||>) :: (Show t, Ord t, IsAltExpr i, HasAlts b) => i t a -> b t a -> AltExprs t a infixr 3 Source #

Add an AltExpr to a list of AltExpr The resuling '[] :. AltExpr' forms the right-hand side of a rule.

Semantic actions

(<$$>) :: (Show t, Ord t, IsSymbExpr s) => (a -> b) -> s t a -> AltExpr t b infixl 4 Source #

Form an AltExpr by mapping some semantic action overy the result of the second argument.

Nonterminal introduction

(<:=>) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a infixl 2 Source #

Form a rule by giving the name of the left-hand side of the new rule. Use this combinator on recursive non-terminals.

(<::=>) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a infixl 2 Source #

Variant of <:=> for recursive non-terminals that have a potentially infinite number of derivations for some input string.

A non-terminal yields infinitely many derivations if and only if it is left-recursive and would be left-recursive if all the right-hand sides of the productions of the grammar are reversed.

chooses :: (Show t, Ord t, IsAltExpr alt) => String -> [alt t a] -> SymbExpr t a Source #

Variant of <::=> that can be supplied with a list of alternates

chooses_prec :: (Show t, Ord t, IsAltExpr alt) => String -> [alt t a] -> SymbExpr t a Source #

Variant of <::= that can be supplied with a list of alternates

Types

Grammar (combinator expression) types

type BNF t a = SymbExpr t a Source #

A combinator expression representing a BNF-grammar. The terminals of the grammar are of type t. When used to parse, the expression yields semantic results of type a.

data SymbExpr t a Source #

A combinator expression representing a symbol. A SymbExpr either represents a terminal or a nonterminal. In the latter case it is constructed with (a variant of) <:=> and adds a rule to the grammar of which the represented symbol is the left-hand side.

Instances

IsAltExpr SymbExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toAlt :: (Show t, Ord t) => SymbExpr t b -> AltExpr t b Source #
HasAlts SymbExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods altsOf :: (Show t, Ord t) => SymbExpr t b -> [AltExpr t b] Source #
IsSymbExpr SymbExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toSymb :: (Show t, Ord t) => SymbExpr t b -> SymbExpr t b Source # mkRule :: (Show t, Ord t) => SymbExpr t b -> BNF t b Source #

data AltExpr t a Source #

A combinator expression representing an alternative: the right-hand side of a production.

Instances

IsAltExpr AltExprs Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toAlt :: (Show t, Ord t) => AltExprs t b -> AltExpr t b Source #
IsAltExpr AltExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toAlt :: (Show t, Ord t) => AltExpr t b -> AltExpr t b Source #
HasAlts AltExprs Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods altsOf :: (Show t, Ord t) => AltExprs t b -> [AltExpr t b] Source #
HasAlts AltExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods altsOf :: (Show t, Ord t) => AltExpr t b -> [AltExpr t b] Source #
IsSymbExpr AltExprs Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toSymb :: (Show t, Ord t) => AltExprs t b -> SymbExpr t b Source # mkRule :: (Show t, Ord t) => AltExprs t b -> BNF t b Source #
IsSymbExpr AltExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toSymb :: (Show t, Ord t) => AltExpr t b -> SymbExpr t b Source # mkRule :: (Show t, Ord t) => AltExpr t b -> BNF t b Source #

type AltExprs = OO [] AltExpr Source #

A list of alternatives represents the right-hand side of a rule.

Parseable token types

data Token Source #

A datatype for representing tokens with some builtins and an aribitrary Token constructor. This datatype stores (optional) lexemes.

Constructors

Char Char
Keyword String
EOS
Epsilon
IntLit (Maybe Int)
FloatLit (Maybe Double)
BoolLit (Maybe Bool)
StringLit (Maybe String)
CharLit (Maybe Char)
IDLit (Maybe String)
AltIDLit (Maybe String)	alternative identifiers, for example functions vs. constructors (as in Haskell).
Token String (Maybe String)

Instances

Eq Token Source #
Instance details Defined in GLL.Types.Grammar Methods (==) :: Token -> Token -> Bool # (/=) :: Token -> Token -> Bool #
Ord Token Source #
Instance details Defined in GLL.Types.Grammar Methods compare :: Token -> Token -> Ordering # (<) :: Token -> Token -> Bool # (<=) :: Token -> Token -> Bool # (>) :: Token -> Token -> Bool # (>=) :: Token -> Token -> Bool # max :: Token -> Token -> Token # min :: Token -> Token -> Token #
Show Token Source #
Instance details Defined in GLL.Types.Grammar Methods showsPrec :: Int -> Token -> ShowS # show :: Token -> String # showList :: [Token] -> ShowS #
SubsumesToken Token Source #
Instance details Defined in GLL.Types.Grammar Methods upcast :: Token -> Token Source # downcast :: Token -> Maybe Token Source #
Parseable Token Source #
Instance details Defined in GLL.Types.Grammar Methods eos :: Token Source # eps :: Token Source # matches :: Token -> Token -> Bool Source # unlex :: Token -> String Source #

class (Ord a, Eq a, Show a) => Parseable a where Source #

Class that captures elements of an input string (tokens).

eos is the end-of-string symbol
eps is the empty-string symbol

Both eos and eps must be distinct from eachother and from all tokens in the input string. The show instance is required to throw error messages.

Minimal complete definition

eos, eps, matches

Methods

eos :: a Source #

eps :: a Source #

matches :: a -> a -> Bool Source #

This function is used for matching grammar tokens and input tokens. Override this method if, for example, your input tokens store lexemes while the grammar tokens do not

unlex :: a -> String Source #

This function pretty-prints the Parseable type by displaying its lexeme. Default implementation is show, which should be replaced for prettier error messages.

Instances

Parseable Char Source #	Assumes `$` and `#` never appear in the input string.
Instance details Defined in GLL.Parseable.Char Methods eos :: Char Source # eps :: Char Source # matches :: Char -> Char -> Bool Source # unlex :: Char -> String Source #
Parseable Token Source #
Instance details Defined in GLL.Types.Grammar Methods eos :: Token Source # eps :: Token Source # matches :: Token -> Token -> Bool Source # unlex :: Token -> String Source #

class SubsumesToken a where Source #

Class whose members are super-types of Token.

Methods

upcast :: Token -> a Source #

downcast :: a -> Maybe Token Source #

Instances

SubsumesToken Token Source #
Instance details Defined in GLL.Types.Grammar Methods upcast :: Token -> Token Source # downcast :: Token -> Maybe Token Source #

unlexTokens :: [Token] -> String Source #

Pretty-prints a list of Tokens as a concatenation of their lexemes.

unlexToken :: Token -> String Source #

Running a parser

grammarOf :: (Show t, Parseable t, IsSymbExpr s) => s t a -> Grammar t Source #

The grammar of a given symbol expression.

parse :: (Show t, Parseable t, IsSymbExpr s) => s t a -> [t] -> [a] Source #

Runs a parser given a string of Parseables and returns a list of semantic results, corresponding to all finitely many derivations.

printParseData :: (Parseable t, IsSymbExpr s, Show a) => s t a -> [t] -> IO () Source #

Print some information about the parse. Helpful for debugging.

evaluatorWithParseData :: (Parseable t, IsSymbExpr s, Show a) => s t a -> [t] -> [a] Source #

Print some information

Running a parser with options

parseWithOptions :: (Show t, Parseable t, IsSymbExpr s) => CombinatorOptions -> s t a -> [t] -> [a] Source #

Run the parser with some CombinatorOptions.

parseWithParseOptions :: (Show t, Parseable t, IsSymbExpr s) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> [a] Source #

Run the parser with some ParseOptions and CombinatorOptions.

printParseDataWithOptions :: (Parseable t, IsSymbExpr s, Show a) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> IO () Source #

Variant of printParseData which can be controlled by ParseOptions

evaluatorWithParseDataAndOptions :: (Parseable t, IsSymbExpr s, Show a) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> [a] Source #

printGrammarData :: (Show t, Parseable t, IsSymbExpr s) => s t a -> IO () Source #

Print some information about the grammar constructed by a IsSymbExpr. useful for debugging purposes

Possible options

type CombinatorOptions = [CombinatorOption] Source #

A list of CombinatorOptions for evaluating combinator expressions.

type CombinatorOption = PCOptions -> PCOptions Source #

A single option.

maximumErrors :: Int -> CombinatorOption Source #

Set the maximum number of errors shown in case of an unsuccessful parse.

throwErrors :: CombinatorOption Source #

If there are no parse results, the default behaviour is to return an empty list. If this option is used, a runtime error will be reported, with debugging information.

maximumPivot :: CombinatorOption Source #

Enables a 'longest-match' at production level.

maximumPivotAtNt :: CombinatorOption Source #

Enables 'longest-match' at non-terminal level.

leftBiased :: CombinatorOption Source #

Turns all occurrences of <||> into a 'left biased' variant: only return results of the second alternate if the first alternate does not have any results.

Parser options

fullSPPF :: ParseOption Source #

Create the SPPF with all nodes and edges, not necessarily strictly binarised.

allNodes :: ParseOption Source #

Create all nodes, but no edges between nodes.

packedNodesOnly :: ParseOption Source #

Create packed-nodes only.

strictBinarisation :: ParseOption Source #

Fully binarise the SPPF, resulting in a larger SPPF and possibly slower runtimes. When this flag is on, packed nodes can only have a single symbol node child or one intermediate node child and one symbol node child. With the flag disabled a packed node can have two symbol node children.

noSelectTest :: ParseOption Source #

Turn of select tests. Disables lookahead.

Running a parser with options and explicit failure

parseWithOptionsAndError :: (Show t, Parseable t, IsSymbExpr s) => CombinatorOptions -> s t a -> [t] -> Either String [a] Source #

Run the parser with some CombinatorOptions and return either an error or the results. Any returned results will be a list of length greater than 0.

parseWithParseOptionsAndError :: (Show t, Parseable t, IsSymbExpr s) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> Either String [a] Source #

Run the parser with some ParseOptions and CombinatorOptions. Returns either an error or the results. Any returned results will be a list of length greater than 0.

Runing a parser to obtain `ParseResult`.

parseResult :: (Show t, Parseable t, IsSymbExpr s) => s t a -> [t] -> ParseResult t Source #

Get the ParseResult, containing an SPPF, produced by parsing the given input with the given parser.

parseResultWithOptions :: (Show t, Parseable t, IsSymbExpr s) => ParseOptions -> CombinatorOptions -> s t a -> [t] -> ParseResult t Source #

Get the ParseResult given some ParseOptions and CombinatorOptions.

data ParseResult t Source #

The ParseResult datatype contains the SPPF and some other information about the parse:

SPPF
Whether the parse was successful
The number of descriptors that have been processed
The number of symbol nodes (nonterminal and terminal)
The number of intermediate noes
The number of packed nodes
The number of GSS nodes
The number of GSS edges

Constructors

ParseResult
Fields sppf_result :: SPPF t res_success :: Bool res_successes :: Int nr_descriptors :: Int nr_nterm_nodes :: Int nr_term_nodes :: Int nr_intermediate_nodes :: Int nr_packed_nodes :: Int nr_packed_node_attempts :: Int nr_sppf_edges :: Int nr_gss_nodes :: Int nr_gss_edges :: Int error_message :: String

Instances

Show (ParseResult t) Source #
Instance details Defined in GLL.Parser Methods showsPrec :: Int -> ParseResult t -> ShowS # show :: ParseResult t -> String # showList :: [ParseResult t] -> ShowS #

Builtin lexers.

default_lexer :: SubsumesToken t => String -> [t] Source #

A lexer using the default LexerSettings.

Lexer settings

lexer :: SubsumesToken t => LexerSettings -> String -> [t] Source #

Variant of lexerEither that throws an error or returns the result otherwise

lexerEither :: SubsumesToken t => LexerSettings -> String -> Either String [t] Source #

A lexer parameterised by LexerSettings.

data LexerSettings Source #

Settings for changing the behaviour of the builtin lexer lexer. Lexers are built using Text.Regex.Applicative.

Constructors

LexerSettings

Fields

keychars :: [Char]
Which keychars to recognise? Default: none.
keywords :: [String]
Which keywords to recognise? Default: none.
whitespace :: Char -> Bool
What is considered a whitespace character? Default: isSpace.
lineComment :: String
How does a line comment start? Default: '"//"'.
blockCommentOpen :: String
How does a block comment open? Default: '"'{-'"'.
blockCommentClose :: String
How does a block comment close? Default: '"'-}'"'.
identifiers :: RE Char String
How to recognise identifiers? Default alphanumerical with lowercase alpha start.
altIdentifiers :: RE Char String
How to recognise alternative identifiers? Default alphanumerical with uppercase alpha start.
tokens :: [(String, RE Char String)]
Arbitrary tokens (a,b). a is the token name, b is a regular expression.
signed_int_lits :: Bool
Whether integer literals may be signed positive or negative. Default: False

emptyLanguage :: LexerSettings Source #

The default LexerSettings.

Derived combinators

mkNt :: (Show t, Ord t, IsSymbExpr s) => s t a -> String -> String Source #

Helper function for defining new combinators. Use mkNt to form a new unique non-terminal name based on the symbol of a given SymbExpr and a String that is unique to the newly defined combinator.

Ignoring semantic results

(<$$) :: (Show t, Ord t, IsSymbExpr s) => b -> s t a -> AltExpr t b infixl 4 Source #

Variant of <$$> that ignores the semantic result of its second argument.

(**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t b infixl 4 Source #

Variant of <**> that ignores the semantic result of the first argument.

(<**) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t a infixl 4 Source #

Variant of <**> that ignores the semantic result of the second argument.

EBNF patterns

optional :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t (Maybe a) Source #

Derive either from the given symbol or the empty string.

preferably :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t (Maybe a) Source #

Version of optional that prefers to derive from the given symbol, affects only nullable nonterminal symbols

reluctantly :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t (Maybe a) Source #

Version of optional that prefers to derive the empty string from the given symbol, affects only nullable nonterminal symbols

optionalWithDef :: (Show t, Ord t, IsSymbExpr s) => s t a -> a -> SymbExpr t a Source #

multiple :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a] Source #

Try to apply a parser multiple times (0 or more). The results are returned in a list. In the case of ambiguity the largest list is returned.

multiple1 :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a] Source #

Try to apply a parser multiple times (1 or more). The results are returned in a list. In the case of ambiguity the largest list is returned.

multipleSepBy :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a] Source #

Same as multiple but with an additional separator.

multipleSepBy1 :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a] Source #

Same as multiple1 but with an additional separator.

multipleSepBy2 :: (Show t, Ord t, IsSymbExpr s2, IsSymbExpr s, IsAltExpr s2) => s t a -> s2 t b -> BNF t [a] Source #

Like multipleSepBy1 but matching at least two occurrences of the first argument. The returned list is therefore always of at least length 2. At least one separator will be consumed.

within :: (Show t, Ord t, IsSymbExpr s) => BNF t a -> s t b -> BNF t c -> BNF t b Source #

Place a piece of BNF within two other BNF fragments, ignoring their semantics.

parens :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b Source #

Place a piece of BNF between the characters '(' and ')'.

braces :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b Source #

Place a piece of BNF between the characters '{' and '}'.

brackets :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b Source #

Place a piece of BNF between the characters '[' and ']'.

angles :: (Show t, Ord t, IsSymbExpr s, SubsumesToken t) => s t b -> BNF t b Source #

Place a piece of BNF between the characters < and >.

foldr_multiple :: (IsSymbExpr s, Parseable t) => s t (a -> a) -> a -> BNF t a Source #

foldr_multipleSepBy :: (IsSymbExpr s, Parseable t) => s t (a -> a) -> s t b -> a -> BNF t a Source #

Operator expressions

fromOpTable :: (SubsumesToken t, Parseable t, IsSymbExpr s) => String -> OpTable e -> s t e -> BNF t e Source #

opTableFromList :: [(Double, [(String, Fixity e)])] -> OpTable e Source #

type OpTable e = Map Double [(String, Fixity e)] Source #

A table mapping operator keywords to a Fixity and Assoc It provides a convenient way to build an expression grammar (see fromOpTable).

data Assoc Source #

Constructors

LAssoc
RAssoc
NA

data Fixity e Source #

Constructors

Prefix (String -> e -> e)
Infix (e -> String -> e -> e) Assoc

Disambiguation

(<:=) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a infixl 2 Source #

Variant of <:=> that prioritises productions from left-to-right (or top-to-bottom).

(<::=) :: (Show t, Ord t, HasAlts b) => String -> b t a -> SymbExpr t a infixl 2 Source #

Variant of <::=> that prioritises productions from left-to-right (or top-to-bottom).

(<<<**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t (a -> b) -> s t a -> AltExpr t b infixl 4 Source #

Variant of <**> that applies shortest match on the left operand.

(<**>>>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t (a -> b) -> s t a -> AltExpr t b infixl 4 Source #

Variant of <**> that applies longest match on the left operand.

(<<**>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t b infixl 4 Source #

(<<<**) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t a infixl 4 Source #

Variant <** that applies shortest match on its left operand

(**>>>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t b infixl 4 Source #

(<**>>) :: (Show t, Ord t, IsAltExpr i, IsSymbExpr s) => i t a -> s t b -> AltExpr t a infixl 4 Source #

Variant of <** that applies longest match on its left operand.

longest_match :: (Show t, Ord t, IsAltExpr alt) => alt t a -> AltExpr t a Source #

Apply this combinator to an alternative to turn all underlying occurrences of <**> (or variants) apply 'longest match'.

shortest_match :: (Show t, Ord t, IsAltExpr alt) => alt t a -> AltExpr t a Source #

many :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a] Source #

Try to apply a parser multiple times (0 or more) with shortest match applied to each occurrence of the parser.

many1 :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a] Source #

Try to apply a parser multiple times (1 or more) with shortest match applied to each occurrence of the parser.

some :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a] Source #

Try to apply a parser multiple times (0 or more) with longest match applied to each occurrence of the parser.

some1 :: (Show t, Ord t, IsSymbExpr s) => s t a -> SymbExpr t [a] Source #

Try to apply a parser multiple times (1 or more) with longest match applied to each occurrence of the parser.

manySepBy :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a] Source #

Same as many but with an additional separator.

manySepBy1 :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a] Source #

Same as many1 but with an additional separator.

manySepBy2 :: (Show t, Ord t, IsSymbExpr s2, IsSymbExpr s, IsAltExpr s2) => s t a -> s2 t b -> BNF t [a] Source #

Like multipleSepBy2 but matching the maximum number of occurrences of the first argument as possible (at least 2).

someSepBy :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a] Source #

Same as some1 but with an additional separator.

someSepBy1 :: (Show t, Ord t, IsSymbExpr s, IsSymbExpr s2, IsAltExpr s2) => s t a -> s2 t b -> SymbExpr t [a] Source #

Same as some1 but with an additional separator.

someSepBy2 :: (Show t, Ord t, IsSymbExpr s2, IsSymbExpr s, IsAltExpr s2) => s t a -> s2 t b -> BNF t [a] Source #

Like multipleSepBy2 but matching the minimum number of occurrences of the first argument as possible (at least 2).

Lifting

class HasAlts a where Source #

Class for lifting to AltExprs.

Methods

altsOf :: (Show t, Ord t) => a t b -> [AltExpr t b] Source #

Instances

HasAlts AltExprs Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods altsOf :: (Show t, Ord t) => AltExprs t b -> [AltExpr t b] Source #
HasAlts AltExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods altsOf :: (Show t, Ord t) => AltExpr t b -> [AltExpr t b] Source #
HasAlts SymbExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods altsOf :: (Show t, Ord t) => SymbExpr t b -> [AltExpr t b] Source #

class IsSymbExpr a where Source #

Class for lifting to SymbExpr.

Minimal complete definition

toSymb

Methods

toSymb :: (Show t, Ord t) => a t b -> SymbExpr t b Source #

mkRule :: (Show t, Ord t) => a t b -> BNF t b Source #

Synonym of toSymb for creating derived combinators.

Instances

IsSymbExpr AltExprs Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toSymb :: (Show t, Ord t) => AltExprs t b -> SymbExpr t b Source # mkRule :: (Show t, Ord t) => AltExprs t b -> BNF t b Source #
IsSymbExpr AltExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toSymb :: (Show t, Ord t) => AltExpr t b -> SymbExpr t b Source # mkRule :: (Show t, Ord t) => AltExpr t b -> BNF t b Source #
IsSymbExpr SymbExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toSymb :: (Show t, Ord t) => SymbExpr t b -> SymbExpr t b Source # mkRule :: (Show t, Ord t) => SymbExpr t b -> BNF t b Source #

class IsAltExpr a where Source #

Class for lifting to AltExpr.

Methods

toAlt :: (Show t, Ord t) => a t b -> AltExpr t b Source #

Instances

IsAltExpr AltExprs Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toAlt :: (Show t, Ord t) => AltExprs t b -> AltExpr t b Source #
IsAltExpr AltExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toAlt :: (Show t, Ord t) => AltExpr t b -> AltExpr t b Source #
IsAltExpr SymbExpr Source #
Instance details Defined in GLL.Combinators.Visit.Join Methods toAlt :: (Show t, Ord t) => SymbExpr t b -> AltExpr t b Source #

Memoisation

memo :: (Ord t, Show t, IsSymbExpr s) => MemoRef [a] -> s t a -> SymbExpr t a Source #

This function memoises a parser, given:

A MemoRef pointing to a fresh MemoTable, created using newMemoTable.
The SymbExpr to memoise.

Use memo on those parsers that are expected to derive the same substring multiple times. If the same combinator expression is used to parse multiple times the MemoRef needs to be cleared using memClear.

memo relies on unsafePerformIO and is therefore potentially unsafe. The option useMemoisation enables memoisation. It is off by default, even if memo is used in a combinator expression.

newMemoTable :: MemoRef a Source #

Create a reference to a fresh MemoTable.

memClear :: MemoRef a -> IO () Source #

Clears the MemoTable to which the given reference refers.

type MemoTable a = IntMap (IntMap a) Source #

A MemoTable maps left-extent l to right-extent r to some results a indicating the the substring ranging from l to r is derived with parse result a.

type MemoRef a = IORef (MemoTable a) Source #

An impure reference to a MemoTable.

useMemoisation :: CombinatorOption Source #

Whether to use unsafe memoisation to speed up the enumeration of parse results.

Example usage

Example

Simple disambiguation

Grammar rewrites

Elementary parsers

Elementary parsers using the Token datatype

Elementary character-level parsers

Elementary combinators

Sequencing

Choice

Semantic actions

Nonterminal introduction

Types

Grammar (combinator expression) types

Parseable token types

Running a parser

Running a parser with options

Possible options

Parser options

Running a parser with options and explicit failure

Runing a parser to obtain ParseResult.

Builtin lexers.

Lexer settings

Derived combinators

Ignoring semantic results

EBNF patterns

Operator expressions

Disambiguation

Lifting

Memoisation

Elementary parsers using the `Token` datatype

Runing a parser to obtain `ParseResult`.