Is an Object a Language Object? (original) (raw)

Description

is.language returns TRUE if x is a variable [name](../../base/help/name.html), a [call](../../base/help/call.html), or an[expression](../../base/help/expression.html).

Usage

is.language(x)

Arguments

Note

A name is also known as ‘symbol’, from its type ([typeof](../../base/help/typeof.html)), see [is.symbol](../../base/help/is.symbol.html).

If [typeof](../../base/help/typeof.html)(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 4.6.0 Index]