qmrparser (version 0.1.5)

empty: Empty token

Description

Recognises a null token. This parser always succeeds.

Usage

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

Arguments

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

Details

action s parameter is always "". Error parameters exists for the sake of homogeneity with the rest of functions. It is not used.

Examples

# NOT RUN {
# ok
stream  <- streamParserFromString("Hello world")
( empty()(stream) )[c("status","node")]

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

# }