call_name: Extract function name or namespace of a call

In rlang: Functions for Base Types and Core R and 'Tidyverse' Features

Extract function name or namespace of a call

Description

call_name() and call_ns() extract the function name or namespace of simple calls as a string. They return NULL for complex calls.

• Simple calls: foo(), bar::foo().

• Complex calls: foo()(), bar::foo, foo$bar(), (function() NULL)().

The is_call_simple() predicate helps you determine whether a call is simple. There are two invariants you can count on:

1. If is_call_simple(x) returns TRUE, call_name(x) returns a string. Otherwise it returns NULL.

2. If is_call_simple(x, ns = TRUE) returns TRUE, call_ns() returns a string. Otherwise it returns NULL.

Usage

call_name(call)

call_ns(call)

is_call_simple(x, ns = NULL)

Arguments

call	A defused call.
x	An object to test.
ns	Whether call is namespaced. If NULL, is_call_simple() is insensitive to namespaces. If TRUE, is_call_simple() detects namespaced calls. If FALSE, it detects unnamespaced calls.

Value

The function name or namespace as a string, or NULL if the call is not named or namespaced.

Examples

# Is the function named?
is_call_simple(quote(foo()))
is_call_simple(quote(foo[[1]]()))

# Is the function namespaced?
is_call_simple(quote(list()), ns = TRUE)
is_call_simple(quote(base::list()), ns = TRUE)

# Extract the function name from quoted calls:
call_name(quote(foo(bar)))
call_name(quo(foo(bar)))

# Namespaced calls are correctly handled:
call_name(quote(base::matrix(baz)))

# Anonymous and subsetted functions return NULL:
call_name(quote(foo$bar()))
call_name(quote(foo[[bar]]()))
call_name(quote(foo()()))

# Extract namespace of a call with call_ns():
call_ns(quote(base::bar()))

# If not namespaced, call_ns() returns NULL:
call_ns(quote(bar()))

rlang documentation built on Nov. 4, 2023, 9:06 a.m.