R: Is an Object a Language Object?

is.language {base} | R Documentation

## Is an Object a Language Object?

### Description

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

### Usage

    is.language(x)

### Arguments

`x` | object to be tested.

### Note

A `name` is also known as ‘symbol’, from its type (`typeof`), see `is.symbol`.

If `typeof(x) == "language"`, then `is.language(x)` is always true, but the reverse does not hold as expressions or names `y` also fulfill `is.language(y)`, see the examples.

This is a primitive function.

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

### 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))

[Package base version 4.0.5 Index]