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

Concise view

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.

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

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.

Attributes

B: the desired result type.
f: the function used to transform the value in this register.
Returns:: the value stored in this register applied to f.
Since:: 3.2.0
Source:: registers.scala

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.

Attributes

B: the desired result type.
pf: the parser that produces the function used to transform the value in this register.
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.

This combinator stores a new value into this register.

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

Attributes

x

the value to place in the register.

Since:

3.2.0

Example:

Put-Get Law:

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

Put-Put Law:

r.put(x) *> r.put(y) == r.put(y)

Source:

registers.scala

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.

Attributes

p

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

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

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))

Attributes

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.
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.

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))

Attributes

f: the function used to modify this register's value.
Since:: 3.2.0
Source:: registers.scala

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))

Attributes

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

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.

Attributes

p

the parser to execute with the adjusted state.

x

the value to place into this register.

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

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.

Attributes

p: the parser whose return value is placed in this register.
q: the parser to execute with the adjusted state.
Returns:: the parser that performs q with the modified state.
Since:: 3.2.0
Source:: registers.scala

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.

Attributes

f

the function used to modify the value in this register.

p

the parser to execute with the adjusted state.

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

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))

Attributes

p: the parser to perform.
Returns:: the result of the parser p, if any.
Since:: 3.2.0
Source:: registers.scala

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