# is.recursive

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##### Is an Object Atomic or Recursive?

is.atomic returns TRUE if x is of an atomic type (or NULL) and FALSE otherwise.

is.recursive returns TRUE if x has a recursive (list-like) structure and FALSE otherwise.

Keywords
classes, programming
##### Usage
is.atomic(x)
is.recursive(x)
##### Arguments
x
object to be tested.
##### Details

is.atomic is true for the atomic types ("logical", "integer", "numeric", "complex", "character" and "raw") and NULL.

Most types of objects are regarded as recursive, except for the atomic types, NULL and symbols (as given by as.name). It is common to call the atomic types ‘atomic vectors’, but note that is.vector imposes further restrictions: an object can be atomic but not a vector (in that sense).

These are primitive functions.

##### References

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

is.list, is.language, etc, and the demo("is.things").
library(base) require(stats) is.a.r <- function(x) c(is.atomic(x), is.recursive(x)) is.a.r(c(a = 1, b = 3)) # TRUE FALSE is.a.r(list()) # FALSE TRUE - a list is a list is.a.r(list(2)) # FALSE TRUE is.a.r(lm) # FALSE TRUE is.a.r(y ~ x) # FALSE TRUE is.a.r(expression(x+1)) # FALSE TRUE (nowadays)