object chain
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.
- Source
- chain.scala
- Since
2.2.0
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- chain
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def
left[A](p: Parsley[A], op: ⇒ Parsley[(A, A) ⇒ A], x: A): Parsley[A]
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 parseop
followed by ap
repeatedly. The results of thep
s,x1
throughxn
, are combined with the results of theop
s,f1
throughfn-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. Ifp
orop
fails having consumed input at any point, the whole combinator fails. If nop
could be parsed, this combinator will return a default resultx
.- p
the value to be parsed.
- op
the operator between each value.
- x
the default value to return if no
p
s can be parsed.- returns
a parser that parses alternating
p
andop
, ending in ap
and applies their results left-associatively or returnsx
if nop
was parsed.
scala> import parsley.expr.chain scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Expr, y: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.left(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
infix.left
for a version where the types can vary, ensuring that the associativity is enforced in a type-safe way.
Example: -
def
left1[A](p: Parsley[A], op: ⇒ Parsley[(A, A) ⇒ A]): Parsley[A]
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 parseop
followed by ap
repeatedly. The results of thep
s,x1
throughxn
, are combined with the results of theop
s,f1
throughfn-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. Ifp
orop
fails having consumed input at any point, the whole combinator fails.- p
the value to be parsed.
- op
the operator between each value.
- returns
a parser that parses alternating
p
andop
, ending in ap
and applies their results left-associatively.
scala> import parsley.expr.chain scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Expr, y: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.left1(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
infix.left1
for a version where the types can vary, ensuring that the associativity is enforced in a type-safe way.
Example: -
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def
postfix[A](p: Parsley[A], op: ⇒ Parsley[(A) ⇒ A]): Parsley[A]
This combinator handles left-assocative parsing, and application of, zero or more postfix unary operators to a single value.
This combinator handles left-assocative parsing, and application of, zero or more postfix unary operators to a single value.
First parse a single
p
. Then, parse many repeatedop
s. The result ofp
,x
, is applied to each of the results of theop
s,f1
throughfn
, such thatf1
is applied first andfn
last:fn(fn-1(..f1(x)..))
. This application is then returned as the result of the combinator. Ifp
orop
fails having consumed input at any point, the whole combinator fails.- p
the single value to be parsed.
- op
the postfix operator to repeatedly parser after
p
.- returns
a parser that an initial
p
, then manyop
s, and applies all of the results left-associatively.
scala> import parsley.expr.chain scala> import parsley.character.{digit, string} scala> sealed trait Expr scala> case class Inc(x: Expr) extends Expr scala> case class Dec(x: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.postfix(digit.map(d => Num(d.asDigit)), string("++") #> Inc <|> string("--") #> Dec) scala> expr.parse("1++----") val res0 = Success(Dec(Dec(Inc(Num(1))))) scala> expr.parse("1") val res1 = Success(Num(1)) scala> expr.parse("") val res2 = Failure(..)
- Since
2.2.0
Example: -
def
postfix1[A, B <: A](p: Parsley[A], op: ⇒ Parsley[(A) ⇒ B]): Parsley[B]
This combinator handles left-assocative parsing, and application of, one or more postfix unary operators to a single value.
This combinator handles left-assocative parsing, and application of, one or more postfix unary operators to a single value.
First parse a single
p
. Then, parse at least one repeatedop
s. The result ofp
,x
, is applied to each of the results of theop
s,f1
throughfn
, such thatf1
is applied first andfn
last:fn(fn-1(..f1(x)..))
. This application is then returned as the result of the combinator. Ifp
orop
fails having consumed input at any point, the whole combinator fails.- p
the single value to be parsed.
- op
the postfix operator to repeatedly parser after
p
.- returns
a parser that an initial
p
, then someop
s, and applies all of the results left-associatively.
scala> import parsley.expr.chain scala> import parsley.character.{digit, string} scala> sealed trait Expr scala> case class Inc(x: Expr) extends Expr scala> case class Dec(x: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.postfix1(digit.map(d => Num(d.asDigit)), string("++") #> Inc <|> string("--") #> Dec) scala> expr.parse("1++----") val res0 = Success(Dec(Dec(Inc(Num(1))))) scala> expr.parse("1") val res1 = Failure(..) scala> expr.parse("") val res2 = Failure(..)
- Since
3.0.0
Example: -
def
prefix[A](op: Parsley[(A) ⇒ A], p: Parsley[A]): Parsley[A]
This combinator handles right-assocative parsing, and application of, zero or more prefix unary operators to a single value.
This combinator handles right-assocative parsing, and application of, zero or more prefix unary operators to a single value.
First parse many repeated
op
s. When there are no moreop
s left to parse, parse a singlep
. The result ofp
,x
, is applied to each of the results of theop
s,f1
throughfn
, such thatfn
is applied first andf1
last:f1(f2(..fn(x)..))
. This application is then returned as the result of the combinator. Ifp
orop
fails having consumed input at any point, the whole combinator fails.- op
the prefix operator to repeatedly parse before
p
.- p
the single value to be parsed.
- returns
a parser that parses many
op
s, and a finalp
, and applies all of the results right-associatively.
scala> import parsley.expr.chain scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Negate(x: Expr) extends Expr scala> case class Id(x: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.prefix(char('-') #> Negate <|> char('+') #> Id, digit.map(d => Num(d.asDigit))) scala> expr.parse("--+1") val res0 = Success(Negate(Negate(Id(Num(1))))) scala> expr.parse("1") val res1 = Success(Num(1)) scala> expr.parse("") val res2 = Failure(..)
- Since
2.2.0
Example: -
def
prefix1[A, B <: A](op: Parsley[(A) ⇒ B], p: ⇒ Parsley[A]): Parsley[B]
This combinator handles right-assocative parsing, and application of, one or more prefix unary operators to a single value.
This combinator handles right-assocative parsing, and application of, one or more prefix unary operators to a single value.
First parse at least one repeated
op
s. When there are no moreop
s left to parse, parse a singlep
. The result ofp
,x
, is applied to each of the results of theop
s,f1
throughfn
, such thatfn
is applied first andf1
last:f1(f2(..fn(x)..))
. This application is then returned as the result of the combinator. Ifp
orop
fails having consumed input at any point, the whole combinator fails.- op
the prefix operator to repeatedly parse before
p
.- p
the single value to be parsed.
- returns
a parser that parses some
op
s, and a finalp
, and applies all of the results right-associatively.
scala> import parsley.expr.chain scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Negate(x: Expr) extends Expr scala> case class Id(x: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.prefix1(char('-') #> Negate <|> char('+') #> Id, digit.map(d => Num(d.asDigit))) scala> expr.parse("--+1") val res0 = Success(Negate(Negate(Id(Num(1))))) scala> expr.parse("1") val res1 = Failure(..) scala> expr.parse("") val res2 = Failure(..)
- Since
3.0.0
Example: -
def
right[A](p: Parsley[A], op: ⇒ Parsley[(A, A) ⇒ A], x: A): Parsley[A]
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 parseop
followed by ap
repeatedly. The results of thep
s,x1
throughxn
, are combined with the results of theop
s,f1
throughfn-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. Ifp
orop
fails having consumed input at any point, the whole combinator fails. If nop
could be parsed, this combinator will return a default resultx
.- p
the value to be parsed.
- op
the operator between each value.
- x
the default value to return if no
p
s can be parsed.- returns
a parser that parses alternating
p
andop
, ending in ap
and applies their results right-associatively or returnsx
if nop
was parsed.
scala> import parsley.expr.chain scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Expr, y: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.right(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
infix.right
for a version where the types can vary, ensuring that the associativity is enforced in a type-safe way.
Example: -
def
right1[A](p: Parsley[A], op: ⇒ Parsley[(A, A) ⇒ A]): Parsley[A]
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 parseop
followed by ap
repeatedly. The results of thep
s,x1
throughxn
, are combined with the results of theop
s,f1
throughfn-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. Ifp
orop
fails having consumed input at any point, the whole combinator fails.- p
the value to be parsed.
- op
the operator between each value.
- returns
a parser that parses alternating
p
andop
, ending in ap
and applies their results right-associatively.
scala> import parsley.expr.chain scala> import parsley.character.{digit, char} scala> sealed trait Expr scala> case class Add(x: Expr, y: Expr) extends Expr scala> case class Num(x: Int) extends Expr scala> val expr = chain.right1(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
infix.right1
for a version where the types can vary, ensuring that the associativity is enforced in a type-safe way.
Example: -
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synchronized[T0](arg0: ⇒ T0): T0
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Binary Operator Chains
These chains allow for the chaining together of values and binary operators in either left- or right-associative application.
Unary Operator Chains
These chains allow for the chaining together and application of multiple prefix or postfix unary operators to a single value.
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.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.