Is object a call?
This function tests if x
is a call. This is a
pattern-matching predicate that returns FALSE
if name
and n
are supplied and the call does not match these properties.
is_call(x, name = NULL, n = NULL, ns = NULL)
x |
An object to test. If a formula, the right-hand side is extracted. |
name |
An optional name that the call should match. It is
passed to |
n |
An optional number of arguments that the call should match. |
ns |
The namespace of the call. If Can be a character vector of namespaces, in which case the call
has to match at least one of them, otherwise |
is_lang()
has been soft-deprecated and renamed to is_call()
in
rlang 0.2.0 and similarly for is_unary_lang()
and
is_binary_lang()
. This renaming follows the general switch from
"language" to "call" in the rlang type nomenclature. See lifecycle
section in call2()
.
is_call(quote(foo(bar))) # You can pattern-match the call with additional arguments: is_call(quote(foo(bar)), "foo") is_call(quote(foo(bar)), "bar") is_call(quote(foo(bar)), quote(foo)) # Match the number of arguments with is_call(): is_call(quote(foo(bar)), "foo", 1) is_call(quote(foo(bar)), "foo", 2) # By default, namespaced calls are tested unqualified: ns_expr <- quote(base::list()) is_call(ns_expr, "list") # You can also specify whether the call shouldn't be namespaced by # supplying an empty string: is_call(ns_expr, "list", ns = "") # Or if it should have a namespace: is_call(ns_expr, "list", ns = "utils") is_call(ns_expr, "list", ns = "base") # You can supply multiple namespaces: is_call(ns_expr, "list", ns = c("utils", "base")) is_call(ns_expr, "list", ns = c("utils", "stats")) # If one of them is "", unnamespaced calls will match as well: is_call(quote(list()), "list", ns = "base") is_call(quote(list()), "list", ns = c("base", "")) is_call(quote(base::list()), "list", ns = c("base", "")) # The name argument is vectorised so you can supply a list of names # to match with: is_call(quote(foo(bar)), c("bar", "baz")) is_call(quote(foo(bar)), c("bar", "foo")) is_call(quote(base::list), c("::", ":::", "$", "@"))
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