is_callable

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Is an object callable?

A callable object is an object that can appear in the function position of a call (as opposed to argument position). This includes symbolic objects that evaluate to a function or literal functions embedded in the call.

Usage
is_callable(x)
Arguments
x

An object to test.

Details

Note that strings may look like callable objects because expressions of the form "list"() are valid R code. However, that's only because the R parser transforms strings to symbols. It is not legal to manually set language heads to strings.

Aliases
  • is_callable
Examples
library(rlang) # NOT RUN { # Symbolic objects and functions are callable: is_callable(quote(foo)) is_callable(base::identity) # node_poke_car() lets you modify calls without any checking: lang <- quote(foo(10)) node_poke_car(lang, get_env()) # Use is_callable() to check an input object is safe to put as CAR: obj <- base::identity if (is_callable(obj)) { lang <- node_poke_car(lang, obj) } else { abort("`obj` must be callable") } eval_bare(lang) # }
Documentation reproduced from package rlang, version 0.2.0, License: GPL-3

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