[Roxygen-devel] parameters with default NULL value

[Felix Andrews]

Hi all,

I was just looking at this thread from a couple of weeks ago:
http://lists.r-forge.r-project.org/pipermail/roxygen-devel/2010-January/000115.html
proposing a change to the function parse.formals in parse.R.

However a more complete change is required to fix not just the "NULL"
bug but also the problem with long default arguments.

Rather than

  if (is.null(formals)) formals
  else list(formals=Map(function(formal)
              if (is.null(formal)) ''
              else if (is.call(formal)) capture.output(formal)
              else as.character(maybe.quote(formal)), formals))

I propose

  if (is.null(formals)) formals
  else list(formals = lapply(formals, function(formal)
      paste(deparse(formal, width=500, control=c()), collapse = "")
    )


Example:

foo <- function(x, d = NULL, a = "hi", asdasd = list(asd = list(x = 1)))
    { x }

lapply(formals(foo), function(formal)
      paste(deparse(formal, width=500, control=c()), collapse = "")
    )
$x
[1] ""

$d
[1] "NULL"

$a
[1] "\"hi\""

$asdasd
[1] "list(asd = list(x = 1))"




-- 
Felix Andrews / 安福立
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The Australian National University
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