Is object a node or pairlist?

Description

• is_pairlist() checks that x has type pairlist.

• is_node() checks that x has type pairlist or language. It tests whether x is a node that has a CAR and a CDR, including callable nodes (language objects).

• is_node_list() checks that x has type pairlist or NULL. NULL is the empty node list.

Usage

is_pairlist(x)

is_node(x)

is_node_list(x)

Arguments

Life cycle

These functions are experimental. We are still figuring out a good naming convention to refer to the different lisp-like lists in R.

See Also

is_call() tests for language nodes.