charParser: Specific single character token.

In qmrparser: Parser Combinator in R

Specific single character token.

Description

Recognises a specific single character.

Usage

  
  charParser(char,
            action = function(s) list(type="char",value=s), 
            error  = function(p) list(type="char",pos  =p)) 

Arguments

char	character to be recognised
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

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

See Also

keyword

Examples

# fail
stream  <- streamParserFromString("H")
( charParser("a")(stream) )[c("status","node")]

# ok 
stream  <- streamParserFromString("a")
( charParser("a")(stream) )[c("status","node")]

# ok 
( charParser("\U00B6")(streamParserFromString("\U00B6")) )[c("status","node")]

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