is.language               package:base               R Documentation

Is an Object a Language Object?

Description:

     `is.language' returns `TRUE' if `x' is either a variable `name', a
     `call', or an `expression'.

Usage:

     is.language(x)

Arguments:

       x: object to be tested.

Examples:

     ll <- list(a = expression(x^2 - 2*x + 1), b = as.name("Jim"),
                c = as.expression(exp(1)), d = call("sin", pi))
     sapply(ll, typeof)
     sapply(ll, mode)
     stopifnot(sapply(ll, is.language))

