object infix
This module contains the very useful chaining family of combinators, which are mostly used to parse operators and expressions of varying fixities. It is a more low-level API compared with precedence.
Compared with the combinators in chain, these allow for more freedom in the type of the values and the operators.
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- infix.scala
- Since
4.0.0
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- infix
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- def left[A, B, C >: B](p: Parsley[A], op: => Parsley[(C, A) => B], x: C)(implicit wrap: (A) => C): Parsley[C]
This combinator handles left-associative parsing, and application of, zero or more binary operators between zero or more values.
This combinator handles left-associative parsing, and application of, zero or more binary operators between zero or more values.
First parse
p, then parseopfollowed by aprepeatedly. The results of theps,x1throughxn, are combined with the results of theops,f1throughfn-1, with left-associative application:fn-1(fn-2(..f1(x1, x2).., xn-1), xn). This application is then returned as the result of the combinator. Ifporopfails having consumed input at any point, the whole combinator fails. If nopcould be parsed, this combinator will return a default resultx.Compared with
chain.left, this combinator allows the types of the operators to more accurately encode their associativity in their types. The recursive values of typeCmay only be applied on the left-hand side of the operators.- A
the type of the values.
- B
the type returned by the operator, which must be a subtype of the result type
C.- C
the result type of the chain, which also fits into the recursive application site of the operators.
- p
the value to be parsed.
- op
the operator between each value.
- x
the default value to return if no
ps can be parsed.- wrap
a function that can convert the value type into the result type, this is provided automatically when
A <:< C.- returns
a parser that parses alternating
pandop, ending in apand applies their results left-associatively or returnsxif nopwas parsed.
scala> import parsley.expr.infix scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Expr, y: Num) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = infix.left[Num, Add, Expr](digit.map(d => Num(d.asDigit)), char('+') #> Add, Num(0)) scala> expr.parse("1+2+3+4") val res0 = Success(Add(Add(Add(Num(1), Num(2)), Num(3)), Num(4))) scala> expr.parse("") val res1 = Success(Num(0))
- Since
4.0.0
- See also
chain.leftfor a version where the types must match, allowing for flexibility to change the associativity.
Example: - def left1[A, B, C >: B](p: Parsley[A], op: => Parsley[(C, A) => B])(implicit wrap: (A) => C): Parsley[C]
This combinator handles left-associative parsing, and application of, zero or more binary operators between one or more values.
This combinator handles left-associative parsing, and application of, zero or more binary operators between one or more values.
First parse
p, then parseopfollowed by aprepeatedly. The results of theps,x1throughxn, are combined with the results of theops,f1throughfn-1, with left-associative application:fn-1(fn-2(..f1(x1, x2).., xn-1), xn). This application is then returned as the result of the combinator. Ifporopfails having consumed input at any point, the whole combinator fails.Compared with
chain.left1, this combinator allows the types of the operators to more accurately encode their associativity in their types. The recursive values of typeCmay only be applied on the left-hand side of the operators.- A
the type of the values.
- B
the type returned by the operator, which must be a subtype of the result type
C.- C
the result type of the chain, which also fits into the recursive application site of the operators.
- p
the value to be parsed.
- op
the operator between each value.
- wrap
a function that can convert the value type into the result type, this is provided automatically when
A <:< C.- returns
a parser that parses alternating
pandop, ending in apand applies their results left-associatively.
scala> import parsley.expr.infix scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Expr, y: Num) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = infix.left1[Num, Add, Expr](digit.map(d => Num(d.asDigit)), char('+') #> Add) scala> expr.parse("1+2+3+4") val res0 = Success(Add(Add(Add(Num(1), Num(2)), Num(3)), Num(4))) scala> expr.parse("") val res1 = Failure(..)
- Since
4.0.0
- See also
chain.left1for a version where the types must match, allowing for flexibility to change the associativity.
Example: - final def ne(arg0: AnyRef): Boolean
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- def right[A, B, C >: B](p: Parsley[A], op: => Parsley[(A, C) => B], x: C)(implicit wrap: (A) => C): Parsley[C]
This combinator handles right-associative parsing, and application of, zero or more binary operators between zero or more values.
This combinator handles right-associative parsing, and application of, zero or more binary operators between zero or more values.
First parse
p, then parseopfollowed by aprepeatedly. The results of theps,x1throughxn, are combined with the results of theops,f1throughfn-1, with right-associative application:f1(x1, f2(x2, ..fn-1(xn-1, xn)..)). This application is then returned as the result of the combinator. Ifporopfails having consumed input at any point, the whole combinator fails. If nopcould be parsed, this combinator will return a default resultx.Compared with
chain.right, this combinator allows the types of the operators to more accurately encode their associativity in their types. The recursive values of typeCmay only be applied on the right-hand side of the operators.- A
the type of the values.
- B
the type returned by the operator, which must be a subtype of the result type
C.- C
the result type of the chain, which also fits into the recursive application site of the operators.
- p
the value to be parsed.
- op
the operator between each value.
- x
the default value to return if no
ps can be parsed.- wrap
a function that can convert the value type into the result type, this is provided automatically when
A <:< C.- returns
a parser that parses alternating
pandop, ending in apand applies their results right-associatively or returnsxif nopwas parsed.
scala> import parsley.expr.infix scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Num, y: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = infix.right[Num, Add, Expr](digit.map(d => Num(d.asDigit)), char('+') #> Add, Num(0)) scala> expr.parse("1+2+3+4") val res0 = Success(Add(Num(1), Add(Num(2), Add(Num(3), Num(4))))) scala> expr.parse("") val res1 = Success(Num(0))
- Since
4.0.0
- See also
chain.rightfor a version where the types must match, allowing for flexibility to change the associativity.
Example: - def right1[A, B, C >: B](p: Parsley[A], op: => Parsley[(A, C) => B])(implicit wrap: (A) => C): Parsley[C]
This combinator handles right-associative parsing, and application of, zero or more binary operators between one or more values.
This combinator handles right-associative parsing, and application of, zero or more binary operators between one or more values.
First parse
p, then parseopfollowed by aprepeatedly. The results of theps,x1throughxn, are combined with the results of theops,f1throughfn-1, with right-associative application:f1(x1, f2(x2, ..fn-1(xn-1, xn)..)). This application is then returned as the result of the combinator. Ifporopfails having consumed input at any point, the whole combinator fails.Compared with
chain.right1, this combinator allows the types of the operators to more accurately encode their associativity in their types. The recursive values of typeCmay only be applied on the right-hand side of the operators.- A
the type of the values.
- B
the type returned by the operator, which must be a subtype of the result type
C.- C
the result type of the chain, which also fits into the recursive application site of the operators.
- p
the value to be parsed.
- op
the operator between each value.
- wrap
a function that can convert the value type into the result type, this is provided automatically when
A <:< C.- returns
a parser that parses alternating
pandop, ending in apand applies their results right-associatively.
scala> import parsley.expr.infix scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Num, y: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = infix.right1[Num, Add, Expr](digit.map(d => Num(d.asDigit)), char('+') #> Add)) scala> expr.parse("1+2+3+4") val res0 = Success(Add(Num(1), Add(Num(2), Add(Num(3), Num(4))))) scala> expr.parse("") val res1 = Failure(..)
- Since
4.0.0
- See also
chain.right1for a version where the types must match, allowing for flexibility to change the associativity.
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This is the documentation for Parsley.
Package structure
The parsley package contains the
Parsleyclass, as well as theResult,Success, andFailuretypes. 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.Parsleycontains the bulk of the core "function-style" combinators.parsley.combinatorcontains many helpful combinators that simplify some common parser patterns.parsley.charactercontains the combinators needed to read characters and strings, as well as combinators to match specific sub-sets of characters.parsley.debugcontains debugging combinators, helpful for identifying faults in parsers.parsley.extensioncontains syntactic sugar combinators exposed as implicit classes.parsley.iocontains extension methods to run parsers with input sourced from IO sources.parsley.exprcontains the following sub modules:parsley.expr.chaincontains combinators used in expression parsingparsley.expr.precedenceis a builder for expression parsers built on a precedence table.parsley.expr.infixcontains combinators used in expression parsing, but with more permissive types than their equivalents inchain.parsley.expr.mixedcontains 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.implicitscontains several implicits to add syntactic sugar to the combinators. These are sub-categorised into the following sub modules:parsley.implicits.charactercontains implicits to allow you to use character and string literals as parsers.parsley.implicits.combinatorcontains implicits related to combinators, such as the ability to make any parser into aParsley[Unit]automatically.parsley.implicits.liftenables postfix application of the lift combinator onto a function (or value).parsley.implicits.zippedenables 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.zippedmethod for building tuples out of several combinators.parsley.errorscontains modules to deal with error messages, their refinement and generation.parsley.errors.combinatorprovides combinators that can be used to either produce more detailed errors as well as refine existing errors.parsley.errors.tokenextractorsprovides mixins for common token extraction strategies during error message generation: these can be used to avoid implementingunexpectedTokenin theErrorBuilder.parsley.liftcontains 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.apcontains functions which allow for the application of a parser returning a function to several parsers returning each of the argument types.parsley.registerscontains combinators that interact with the context-sensitive functionality in the form of registers.parsley.tokencontains theLexerclass that provides a host of helpful lexing combinators when provided with the description of a language.parsley.positioncontains parsers for extracting position information.parsley.genericbridgescontains 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.