| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
Text.Parsec.PrattParser
Description
Implements a Pratt ("top down operator precendence") Parser as a layer on top of Parsec. See http://javascript.crockford.com/tdop/tdop.html and http://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-expression-parsing-made-easy/ for descriptions of the algorithm.
A note on type usage
In all of the types used in this module, the type parameters are named as follows:
s=> the stream type which will be parsed (typically String)u=> the user state type for the parser (e.g. '()')m=> the monad underlying the parser (e.g.Identity)e=> the type of the expression returned by the parsero=> the type of operators (typically String).t=> the type of tokens produced from the stream (not actually referenced here, but required to exist by Parsec)
The following instances are required to exist:
- Stream s m t
- Show t
- Monad m
- Ord o
- Show o
- data OperatorPrecedence
- data OperatorInfo s u m e o = OperatorInfo o OperatorPrecedence (LeftDenotation s u m e o)
- data PrefixOperatorInfo s u m e o
- = SimplePrefixOperator o (PrefixBinder s u m e o)
- | PrefixParserOperator o (NullDenotation s u m e)
- type PrecedenceParser s u m e = OperatorPrecedence -> ParsecT s u m e
- type NullDenotation s u m e = PrecedenceParser s u m e -> ParsecT s u m e
- type PrefixBinder s u m e o = PrefixOperatorInfo s u m e o -> e -> e
- type LeftDenotation s u m e o = OperatorInfo s u m e o -> e -> PrecedenceParser s u m e -> ParsecT s u m e
- type ContentStripper s u m a = ParsecT s u m a
- type OperatorParser s u m o = ParsecT s u m o
- operatorInfoPrecedence :: OperatorInfo s u m e o -> OperatorPrecedence
- operatorInfoName :: OperatorInfo s u m e o -> o
- prefixOperatorInfoName :: PrefixOperatorInfo s u m e o -> o
- buildPrattParser :: forall s u m e o t a. Stream s m t => Show t => Monad m => Ord o => Show o => [OperatorInfo s u m e o] -> [PrefixOperatorInfo s u m e o] -> ContentStripper s u m a -> OperatorParser s u m o -> NullDenotation s u m e -> ParsecT s u m e
Documentation
data OperatorPrecedence Source #
Identifies the precedence and associativity of an operator. Higher numbers bind more strongly to the adjacent terms.
Instances
data OperatorInfo s u m e o Source #
Provides all the information needed to handle an infix operator, i.e.
the operator's symbol (type "o", typically a string), precedence,
and its LeftDenotation.
Constructors
| OperatorInfo o OperatorPrecedence (LeftDenotation s u m e o) |
data PrefixOperatorInfo s u m e o Source #
Provides all the information needed to handle a prefix operator, i.e.
the operator's symbol (type "o", typicall a string), and either a
PrefixBinder (for simple operators) or a NullDenotation (for operators
that need to perform additional parsing).
Constructors
| SimplePrefixOperator o (PrefixBinder s u m e o) | |
| PrefixParserOperator o (NullDenotation s u m e) |
type PrecedenceParser s u m e = OperatorPrecedence -> ParsecT s u m e Source #
A PrecedenceParser is a function that, given a precedence, parses expressions which contain operators whose precedence is greater than or equal to the specified precedence.
type NullDenotation s u m e = PrecedenceParser s u m e -> ParsecT s u m e Source #
A NullDenotation is a function that generates a parser for terms that do not have a left hand
term to bind to. It receives a PrecedenceParser as an argument that can be
used to recursively parse an expression.
type PrefixBinder s u m e o = PrefixOperatorInfo s u m e o -> e -> e Source #
a PrefixBinder binds a prefix operator with the expression to its right
type LeftDenotation s u m e o = OperatorInfo s u m e o -> e -> PrecedenceParser s u m e -> ParsecT s u m e Source #
a LeftDenotation is a function for producing a parser that binds to a left hand term. Its arguments are:
- The
OperatorInfoof the operator being parsed - The expression for the term on the left
- A function that can be used to parse additional terms up to a given precedence (which should usually be the precedence of the operator itself).
type ContentStripper s u m a = ParsecT s u m a Source #
type of parser transformers that can be used to remove extraneous text (eg removing whitespace and/or comments) before a useful token occurs
type OperatorParser s u m o = ParsecT s u m o Source #
Type for defining a parser that returns operator symbols.
operatorInfoPrecedence :: OperatorInfo s u m e o -> OperatorPrecedence Source #
Return the precedence of an infix operator
operatorInfoName :: OperatorInfo s u m e o -> o Source #
Return the symbol of an infix operator
prefixOperatorInfoName :: PrefixOperatorInfo s u m e o -> o Source #
Return the symbol of a prefix operator
buildPrattParser :: forall s u m e o t a. Stream s m t => Show t => Monad m => Ord o => Show o => [OperatorInfo s u m e o] -> [PrefixOperatorInfo s u m e o] -> ContentStripper s u m a -> OperatorParser s u m o -> NullDenotation s u m e -> ParsecT s u m e Source #
Builds a Pratt parser for expressions with a given set of operators and parsers for individual components. The arguments are:
- A list of infix operator descriptions
- A list of prefix operator descriptions
- A content stripper (a parser whose return value is ignored, which strips whitespacecommentsanything else that isn't part of the expression
- An operator parser, which returns symbols as used in the operator descriptions
- A
NullDenotationthat parses individual terms and recursively calls back into the parser to bind expressions to them.