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Extract function name or namespace of a call

Source: R/call.R
call_name.Rd

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()))
#> [1] TRUE
is_call_simple(quote(foo[[1]]()))
#> [1] FALSE

# Is the function namespaced?
is_call_simple(quote(list()), ns = TRUE)
#> [1] FALSE
is_call_simple(quote(base::list()), ns = TRUE)
#> [1] TRUE

# Extract the function name from quoted calls:
call_name(quote(foo(bar)))
#> [1] "foo"
call_name(quo(foo(bar)))
#> [1] "foo"

# Namespaced calls are correctly handled:
call_name(quote(base::matrix(baz)))
#> [1] "matrix"

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

# Extract namespace of a call with call_ns():
call_ns(quote(base::bar()))
#> [1] "base"

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