repetition0N: Repeats one parser

In qmrparser: Parser Combinator in R

Repeats one parser

Description

Repeats a parser indefinitely, while it succeeds. It will return an empty token if the parser never succeeds,

Number of repetitions may be zero.

Usage

  
  repetition0N(rpa0, 
               action = function(s)            list(type="repetition0N",value=s   ), 
               error  = function(p,h) list(type="repetition0N",pos=p,h=h)) 

Arguments

rpa0	parse to be applied iteratively
action	Function to be executed if recognition succeeds. It takes as input parameters information derived from parsers involved as parameters
error	Function to be executed if recognition does not succeed. I takes two parameters: p with position where parser, streamParser, starts its recognition, obtained with streamParserPosition h with information obtained from parsers involved as parameters, normally related with failure(s) position in component parsers. Its information depends on how parser involved as parameters are combined and on the error definition in these parsers.

Details

In case of at least one success, action gets the node returned by the parser repetition1N after applying the parser to be repeated. Otherwise, it gets the node corresponding to token empty: list(type="empty" ,value="")

Functionerror is never called. It is defined as parameter for the sake of homogeneity with the rest of functions.

Value

Anonymous functions, returning a list.

function(stream) –> list(status,node,stream)

From these input parameters, an anonymous function is constructed. This function admits just one parameter, stream, with streamParser class, and returns a three-field list:

• status

  "ok" or "fail"

• node

  With action or error function output, depending on the case

• stream

  With information about the input, after success or failure in recognition

Examples

# ok
stream  <- streamParserFromString("Hello world")
( repetition0N(symbolic())(stream) )[c("status","node")]


# ok
stream  <- streamParserFromString("123 Hello world")
( repetition0N(symbolic())(stream) )[c("status","node")]

qmrparser documentation built on April 24, 2022, 1:05 a.m.