Find leaves of an Rd object using a predicate — Rdo_locate

Apply a function to the character leaves of an Rd object and return the indices of those for which the result is TRUE.

Usage

Rdo_locate_leaves(object, f = function(x) TRUE)

Arguments

object: the object to be examined, usually a list.
f: a function (predicate) returning TRUE for elements with the desired property.

Details

object can be any list whose elements are character strings or lists. The structure is examined recursively. If object is a character vector, it is enclosed in a list.

This function provides a convenient way to locate leaves of an Rd object with a particular content. The function is not limited to Rd objects but it assumes that the elements of object are either lists or charater vectors and currently does not check if this is the case.

todo: describe the case of list() (Rd_tag'ed.)

Value

a list of the positions of the leaves for which the predicate gives TRUE. Each position is an integer vector suitable for the "[[" operator.

Author

Georgi N. Boshnakov

Examples

dummyfun <- function(x) x

fn <- tempfile("dummyfun", fileext = "Rd")
reprompt(dummyfun, filename = fn)
#> Rd source not supplied, looking for installed documentation.
#> Rd source not supplied and installed documentation not found.
#> Trying a 'prompt' function to generate documentation for the object.
#> Error in reprompt(dummyfun, filename = fn): unsuccessful attempt to create Rd doc. using a 'prompt' function.
rdo <- tools::parse_Rd(fn)
#> Warning: cannot open file '/tmp/RtmpnmJSSB/dummyfun16ad11ac887eRd': No such file or directory
#> Error in file(con, "r"): cannot open the connection

f <-  function(x) Rdo_is_newline(x)

nl <- Rdo_locate_leaves(rdo, f )
#> Error: object 'rdo' not found

length(nl)  # there are quite a few newline leaves!
#> Error: object 'nl' not found

unlink(fn)