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)

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)
sapply(ll, is.language)# all TRUE