commentParser: Comment token.

In qmrparser: Parser Combinator in R

Comment token.

Description

Recognises a comment, a piece of text delimited by two predefined tokens.

Usage

  
  commentParser(beginComment,endComment,
          action = function(s) list(type="commentParser",value=s),
          error  = function(p) list(type="commentParser",pos  =p))

Arguments

beginComment	String indicating comment beginning
endComment	String indicating comment end
action	Function to be executed if recognition succeeds. Character stream making up the token is passed as parameter to this function
error	Function to be executed if recognition does not succeed. Position of streamParser obtained with streamParserPosition is passed as parameter to this function

Details

Characters preceded by \ are not considered as part of beginning of comment end.

Value

Anonymous function, returning a list.

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

From input parameters, an anonymous function is defined. This function admits just one parameter, stream, with type streamParser, 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

# fail
stream  <- streamParserFromString("123")
( commentParser("(*","*)")(stream) )[c("status","node")]

# ok 
stream  <- streamParserFromString("(*123*)")
( commentParser("(*","*)")(stream) )[c("status","node")]

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