string: Token string

In qmrparser: Parser Combinator in R

Token string

Description

Any character sequence, by default using simple or double quotation marks.

Usage

string(isQuote= function(c) switch(c,'"'=,"'"=TRUE,FALSE),
       action = function(s) list(type="string",value=s), 
       error  = function(p) list(type="string",pos  =p)) 

Arguments

isQuote	Predicate indicating whether a character begins and ends a string
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 string 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("Hello world")
( string()(stream) )[c("status","node")]

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

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