If the "keep.source"
option is TRUE
, R's parser
will attach detailed information on the object it has parsed. These
functions retrieve that information.
getParseData(x, includeText = NA)
getParseText(parseData, id)
an expression returned from parse
, or a function or other
object with source reference information
logical; whether to include the text of parsed items in the result
a data frame returned from getParseData
a vector of item identifiers whose text is to be retrieved
For getParseData
:
If parse data is not present, NULL
. Otherwise
a data frame is returned, containing the following columns:
integer. The line number where the item starts. This is the
parsed line number called "parse"
in getSrcLocation
,
which ignores #line
directives.
integer. The column number where the item starts. The first character
is column 1. This corresponds to "column"
in getSrcLocation
.
integer. The line number where the item ends.
integer. The column number where the item ends.
integer. An identifier associated with this item.
integer. The id
of the parent of this item.
character string. The type of the token.
logical. Whether the token is “terminal”, i.e. a leaf in the parse tree.
character string. If includeText
is TRUE
, the
text of all tokens; if it is NA
(the default), the text of terminal
tokens. If includeText == FALSE
, this column is not included.
Very long strings (with source of 1000 characters or more) will not be stored;
a message giving their length and delimiter will be included instead.
The rownames of the data frame will be equal to the id values, and the data frame will have a "srcfile" attribute containing the srcfile record which was used. The rows will be ordered by starting position within the source file, with parent items occurring before their children.
For getParseText: A character vector of the same length as id containing the associated text items. If they are not included in parseData, they will be retrieved from the original file.
In version 3.0.0, the R parser was modified to include code written
by Romain Francois in his parser package. This constructs a
detailed table of information about every token and higher level
construct in parsed code. This table is stored in the
srcfile
record associated with source references in the
parsed code, and retrieved by the getParseData
function.
Romain Francois (2012). parser: Detailed R source code parser. R package version 0.0-16. https://github.com/halpo/parser.
fn <- function(x) {
x + 1 # A comment, kept as part of the source
}
d <- getParseData(fn)
if (!is.null(d)) {
plus <- which(d$token == "'+'")
sum <- d$parent[plus]
print(d[as.character(sum),])
print(getParseText(d, sum))
}
Run the code above in your browser using DataLab