is.vector <- function(x, mode="any") .Internal(is.vector(x,mode))
## is.finite <- function(x) !is.na(x)

is.name <- is.symbol # which is Primitive
##Was is.symbol <- function(x) typeof(x)=="symbol"


"is.na<-" <- function(x, value) UseMethod("is.na<-")

"is.na<-.default" <- function(x, value)
{
    x[value] <- NA
    x
}

is.primitive <- function(x)
    switch(typeof(x),
	   "special" = , "builtin" = TRUE,
	   FALSE)