function.
as.function(x) is.function(x)
as.function merely changes the mode of
x to
"function".
is.function tests whether
x is a function.
Both of these functions are generic; currently there are no methods written for either of them.
polynom <- function(x)
{
x^2 + 3 * x - 6
}
is.function(polynom) # returns TRUE