For this application I would use names(formals(object)) to extract the
formal arguments.

luke

On Mon, 7 Feb 2011, William Dunlap wrote:

I was looking for all the glm-related 'family' functions
in stats using the following predicate that returns TRUE
for any function whose first argument is called "link".
  is.family <- function(object) is.function(object) &&
           identical(names(as.list(object))[1], "link")

It threw an error when applied to SSfol
  > is.family(SSfol)
  Error in as.vector(x, "list") :
    cannot coerce type 'closure' to vector of type 'list'
but works when I unclass SSfol
  > is.family(unclass(SSfol))
  [1] FALSE

It looks like as.list fails on any function that is assigned
a class:
  > as.list(function(x)x+1)
  $x


  [[2]]
  x + 1

  > as.list(structure(function(x)x+1, class="unrecognized class name"))
  Error in as.vector(x, "list") :
    cannot coerce type 'closure' to vector of type 'list'

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

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--
Luke Tierney
Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
   Actuarial Science
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