package tokenextractors
This package contains implementations of token extractors that can be mixed into ErrorBuilder
to decide how to extract unexpected tokens from the residual input left over from a parse error.
These are common strategies, and something here is likely to be what is needed. They are all careful to handle unprintable characters and whitespace in a sensible way, and account for unicode codepoints that are wider than a single 16-bit character.
- Source
- package.scala
- Since
4.0.0
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Type Members
- trait LexToken extends AnyRef
This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will try and parse the residual input to identify a valid lexical token to report.This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will try and parse the residual input to identify a valid lexical token to report.When parsing a grammar that as a dedicated lexical distinction, it is nice to be able to report problematic tokens relevant to that grammar as opposed to generic input lifted straight from the input stream. The easiest way of doing this would be having a pre-lexing pass and parsing based on tokens, but this is deliberately not how Parsley is designed. Instead, this extractor can try and parse the remaining input to try and identify a token on demand.
If the
lexicalError
flag of theunexpectedToken
method is not set, which would indicate a problem within a token reported by a classical lexer and not the parser, the extractor will try to parse each of the providedtokens
in turn: whichever is the longest matched of these tokens will be reported as the problematic one (this can be changed by overridingselectToken
). For best effect, these tokens should not consume whitespace (which would otherwise be included at the end of the token!): this means that, if using theLexer
class, the functionality innonlexeme
should be used. If one of the givens tokens cannot be parsed, the input until the next valid parsable token (or end of input) is returned as aToken.Raw
.Currently, if
lexicalError
is true, this extractor will just return the next character as the problematic item (this may be changed by overriding theextractItem
method).- Since
4.0.0
- trait MatchParserDemand extends AnyRef
This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will make a token as wide as the amount of input the parser tried to consume when it failed.This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will make a token as wide as the amount of input the parser tried to consume when it failed.- Since
4.0.0
- Note
In the case of unprintable characters or whitespace, this extractor will favour reporting a more meaningful name.
- trait SingleChar extends AnyRef
This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will unconditionally report the first character in the remaining input as the problematic token.This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will unconditionally report the first character in the remaining input as the problematic token.- Since
4.0.0
- Note
In the case of unprintable characters or whitespace, this extractor will favour reporting a more meaningful name.
- trait TillNextWhitespace extends AnyRef
This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will construct a token that extends to the next available whitespace in the remaining input.This extractor mixin provides an implementation for
ErrorBuilder.unexpectedToken
when mixed into an error builder: it will construct a token that extends to the next available whitespace in the remaining input. It can be configured to constrict this token to the minimum of the next whitespace or whatever the parser demanded (seeMatchParserDemand
).- Since
4.0.0
- Note
In the case of unprintable characters or whitespace, this extractor will favour reporting a more meaningful name.
Value Members
- object LexToken
This object contains helper functions useful for interacting with
LexToken
.This object contains helper functions useful for interacting with
LexToken
.- Since
4.0.0
- object MatchParserDemand
Contains the functionality of
MatchParserDemand
as a function.Contains the functionality of
MatchParserDemand
as a function.- Since
4.0.0
- object SingleChar
Contains the functionality of
SingleChar
as a function.Contains the functionality of
SingleChar
as a function.- Since
4.0.0
- object TillNextWhitespace
Contains the functionality of
TillNextWhitespace
as a function.Contains the functionality of
TillNextWhitespace
as a function.- Since
4.0.0
This is the documentation for Parsley.
Package structure
The parsley package contains the
Parsley
class, as well as theResult
,Success
, andFailure
types. In addition to these, it also contains the following packages and "modules" (a module is defined as being an object which mocks a package):parsley.Parsley
contains the bulk of the core "function-style" combinators.parsley.combinator
contains many helpful combinators that simplify some common parser patterns.parsley.character
contains the combinators needed to read characters and strings, as well as combinators to match specific sub-sets of characters.parsley.debug
contains debugging combinators, helpful for identifying faults in parsers.parsley.extension
contains syntactic sugar combinators exposed as implicit classes.parsley.io
contains extension methods to run parsers with input sourced from IO sources.parsley.expr
contains the following sub modules:parsley.expr.chain
contains combinators used in expression parsingparsley.expr.precedence
is a builder for expression parsers built on a precedence table.parsley.expr.infix
contains combinators used in expression parsing, but with more permissive types than their equivalents inchain
.parsley.expr.mixed
contains combinators that can be used for expression parsing, but where different fixities may be mixed on the same level: this is rare in practice.parsley.implicits
contains several implicits to add syntactic sugar to the combinators. These are sub-categorised into the following sub modules:parsley.implicits.character
contains implicits to allow you to use character and string literals as parsers.parsley.implicits.combinator
contains implicits related to combinators, such as the ability to make any parser into aParsley[Unit]
automatically.parsley.implicits.lift
enables postfix application of the lift combinator onto a function (or value).parsley.implicits.zipped
enables boths a reversed form of lift where the function appears on the right and is applied on a tuple (useful when type inference has failed) as well as a.zipped
method for building tuples out of several combinators.parsley.errors
contains modules to deal with error messages, their refinement and generation.parsley.errors.combinator
provides combinators that can be used to either produce more detailed errors as well as refine existing errors.parsley.errors.tokenextractors
provides mixins for common token extraction strategies during error message generation: these can be used to avoid implementingunexpectedToken
in theErrorBuilder
.parsley.lift
contains functions which lift functions that work on regular types to those which now combine the results of parsers returning those same types. these are ubiquitous.parsley.ap
contains functions which allow for the application of a parser returning a function to several parsers returning each of the argument types.parsley.registers
contains combinators that interact with the context-sensitive functionality in the form of registers.parsley.token
contains theLexer
class that provides a host of helpful lexing combinators when provided with the description of a language.parsley.position
contains parsers for extracting position information.parsley.genericbridges
contains some basic implementations of the Parser Bridge pattern (see Design Patterns for Parser Combinators in Scala, or the parsley wiki): these can be used before more specialised generic bridge traits can be constructed.