arg | R Documentation |
arg(x)
looks in the calling environment for the binding x
,
taken literally, and returns it as a quotation. arg(x)
is
equivalent to unwrap(quo(x))
.
arg_
evaluates the first element normally;
arg(x, e)
is equivalent to arg_(quote(x), e)
.
arg_list
looks up multiple variables, and returns a dots
object. arg_list(x, y)
is equivalent to unwrap(dots(x=x, y=y))
. If any of the requested variables are not bound, an error
will be raised.
arg_list_
is a normally evaluating version of arg_list
;
arg_list(x, y)
is equivalent to
arg_list_(alist(x, y), environment())
.
set_arg
and set_arg_ create bindings from quotations. They
replace base function delayedAssign.
arg(sym, env = arg_env_(quote(sym), environment()))
arg_(sym, env = arg_env(sym, environment()))
arg_list(...)
arg_list_(syms, envs)
set_arg(dst, src)
set_arg_(dst, src)
sym |
The name to look up. For |
env |
The environment to look in. By default, the environment
from which |
... |
Bare names (not forced). Arguments may be named; these names determine the names on the output list. If arguments are not named, the names given are used. |
syms |
A character vector or list of names. |
envs |
An environment, or a list of environments, to look for the bindings in. |
dst |
A name; for |
src |
A quotation (or something that can be converted to a quotation, like a formula). |
arg
returns a quotation object.
args
returns a dots object.
arg_list
returns a dots object.
If you use a a literal character value, as in arg_("x", environment())
, you MUST also give the environment
parameter. The reason is that R will discard scope information
about code literals in byte-compiled code; so when arg_("x")
is
called in compiled code, the default value for env
will be
found to be emptyenv()
.
Beware of writing arg_list(a, b, ...)
which probably
doesn't do what you want. This is because R unwraps ...
before
invoking arg_list
, so this ends up double-unwrapping ...
. To
capture ...
alongside named arguments you can use the syntax
arg_list(x, y, (...))
(which is equivalent to c(arg_list(x, y), dots(...))
). You can also use get_call()
to extract all
function inputs to an active function.
dots get_dots unwrap
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