parsley
4.4.0-M5
API
Generated with
parsley/parsley/registers/Reg

Reg

parsley.registers$.Reg
See theReg companion object
class Reg[A]

This class is used to index registers within the mutable state.

Attributes

Since

2.2.0

Note

it is undefined behaviour to use a register in multiple different independent parsers. You should be careful to parameterise the registers in shared parsers and allocate fresh ones for each "top-level" parser you will run.

Companion
object
Source
registers.scala
Graph
Supertypes
class Object
trait Matchable
class Any

Members list

Grouped members

Getters

These combinators allow for the retrieval of the stateful value of a register, and injecting it into the parsing context. Does not modify the contents of the register itself.

def get: Parsley[A]

This combinator injects the value stored in this register into a parser.

This combinator injects the value stored in this register into a parser.

Allows for the value stored in this register to be purely injected into the parsing context. No input is consumed in this process, and it cannot fail.

Attributes

Returns

a parser that returns the value stored in this register.

Since

3.2.0

Example

Get-Get Law: 

r.get *> r.get == r.get
r.get <~> r.get == r.get.map(x => (x, x))
Source
registers.scala
def gets[B](f: A => B): Parsley[B]

This combinator injects the value stored in this register into a parser after applying a function to it.

This combinator injects the value stored in this register into a parser after applying a function to it.

Allows for the value stored in this register to be purely injected into the parsing context but the function f is applied first. No input is consumed in this process, and it cannot fail.

Type parameters

B

the desired result type.

Value parameters

f

the function used to transform the value in this register.

Attributes

Returns

the value stored in this register applied to f.

Since

3.2.0

Source
registers.scala
def gets[B](pf: Parsley[A => B]): Parsley[B]

This combinator injects the value stored in this register into a parser after applying a function obtained from a parser to it.

This combinator injects the value stored in this register into a parser after applying a function obtained from a parser to it.

First, pf is parsed, producing the function f on success. Then, the value stored in this register x is applied to the function f. The combinator returns f(x). Only pf is allowed to consume input. If pf fails, the combinator fails, otherwise it will succeed.

Type parameters

B

the desired result type.

Value parameters

pf

the parser that produces the function used to transform the value in this register.

Attributes

Returns

the value stored in this register applied to a function generated from pf.

Since

3.2.0

Source
registers.scala

Setters

These combinators directly update the value contained within a register. This new value can be provided directly or sourced from a parser.

def put(x: A): Parsley[Unit]

This combinator stores a new value into this register.

This combinator stores a new value into this register.

Without any other effect, the value x will be placed into this register.

Value parameters

x

the value to place in the register.

Attributes

Since

3.2.0

Example

Put-Get Law: 

r.put(x) *> r.get == r.put(x).as(x)

Put-Put Law: 

r.put(x) *> r.put(y) == r.put(y)
Source
registers.scala
def put(p: Parsley[A]): Parsley[Unit]

This combinator stores a new value into this register.

This combinator stores a new value into this register.

First, parse p to obtain its result x. Then store x into this register without any further effect. If p fails this combinator fails.

Value parameters

p

the parser that produces the value to store in the register.

Attributes

Since

3.2.0

Example

Get-Put Law: 

r.put(r.get) == unit

Put-Put Law: 

// only when `q` does not inspect the value of `r`!
r.put(p) *> r.put(q) == p *> r.put(q)
Source
registers.scala
def puts[B](p: Parsley[B], f: B => A): Parsley[Unit]

This combinator stores a new value into this register.

This combinator stores a new value into this register.

First, parse p to obtain its result x. Then store f(x) into this register without any further effect. If p fails this combinator fails.

Equivalent to 

this.put(p.map(f))

Value parameters

f

a function which adapts the result of p so that it can fit into this register.

p

the parser that produces the value to store in the register.

Attributes

Since

3.0.0

Source
registers.scala

Modification

These combinators modify the value stored within a register by using a function. The function used can be provided directly or sourced from a parser.

def modify(f: A => A): Parsley[Unit]

This combinator modifies the value stored in this register with a function.

This combinator modifies the value stored in this register with a function.

Without any other effect, get the value stored in this register, x, and put back f(x).

Equivalent to 

this.put(this.gets(f))

Value parameters

f

the function used to modify this register's value.

Attributes

Since

3.2.0

Source
registers.scala
def modify(pf: Parsley[A => A]): Parsley[Unit]

This combinator modifies the value stored in this register with a function.

This combinator modifies the value stored in this register with a function.

First, parse pf to obtain its result f. Then get the value stored in this register, x, and put back f(x). If p fails this combinator fails.

Equivalent to 

this.put(this.gets(pf))

Value parameters

pf

the parser that produces the function used to transform the value in this register.

Attributes

Since

3.2.0

Source
registers.scala

Local Modification

These combinators allow for some form of local stateful modification. This means that any changes to the register may be reverted after the execution of the parser: this may be on the parsers success, but it could also involve the parsers failure.

def local[B](x: A)(p: Parsley[B]): Parsley[B]

This combinator changed the value stored in this register for the duration of a given parser, resetting it afterwards.

This combinator changed the value stored in this register for the duration of a given parser, resetting it afterwards.

First get the current value in this register xold, then place x into this register without any further effect. Then, parse p, producing result y on success. Finally, put xold back into this register and return y. If p fails, the whole combinator fails and the state is not restored.

Value parameters

p

the parser to execute with the adjusted state.

x

the value to place into this register.

Attributes

Returns

the parser that performs p with the modified state x.

Since

3.2.0

Example

Put-Put Law: 

r.put(x) *> r.local(y)(p) == r.put(y) *> p <* r.put(x)
Source
registers.scala
def local[B](p: Parsley[A])(q: => Parsley[B]): Parsley[B]

This combinator changed the value stored in this register for the duration of a given parser, resetting it afterwards.

This combinator changed the value stored in this register for the duration of a given parser, resetting it afterwards.

First get the current value in this register xold, then parse p to get the result x, placing it into this register without any further effect. Then, parse q, producing result y on success. Finally, put xold back into this register and return y. If p or q fail, the whole combinator fails and the state is not restored.

Value parameters

p

the parser whose return value is placed in this register.

q

the parser to execute with the adjusted state.

Attributes

Returns

the parser that performs q with the modified state.

Since

3.2.0

Source
registers.scala
def local[B](f: A => A)(p: Parsley[B]): Parsley[B]

This combinator changed the value stored in this register for the duration of a given parser, resetting it afterwards.

This combinator changed the value stored in this register for the duration of a given parser, resetting it afterwards.

First get the current value in this register xold, then place f(xold) into this register without any further effect. Then, parse p, producing result y on success. Finally, put xold back into this register and return y. If p fails, the whole combinator fails and the state is not restored.

Value parameters

f

the function used to modify the value in this register.

p

the parser to execute with the adjusted state.

Attributes

Returns

the parser that performs p with the modified state.

Since

3.2.0

Example

Put-Put Law and Put-Get Law: 

r.put(x) *> r.local(f)(p) == r.put(f(x)) *> p <* r.put(x)
Source
registers.scala
def rollback[B](p: Parsley[B]): Parsley[B]

This combinator rolls-back any changes to this register made by a given parser if it fails.

This combinator rolls-back any changes to this register made by a given parser if it fails.

First get the current value in this register xold. Then parse p, if it succeeds, producing y, then y is returned and this register retains its value post-p. Otherwise, if p failed without consuming input, xold is placed back into this register and this combinator fails.

This can be used in conjunction with local to make an almost unconditional state restore: 

// `r`'s state is always rolled back after `p` unless it fails having consumed input.
r.rollback(r.local(x)(p))

Value parameters

p

the parser to perform.

Attributes

Returns

the result of the parser p, if any.

Since

3.2.0

Source
registers.scala
Generated with