if you want to keep objetcts of class call:
i <- function(...)
{
l <- match.call()
l <- as.list(l)
l <- l[-1]
l
}
i <- function(...)
{
l <- match.call()
l[[1]] <- as.name("expression")
l
}
i(sin(pi), cos(pi/2))
Or maybe you just need the match.call depending what you want to do after. hth