The functions do and do_ construct and invoke a function call.
In combination with dots and quotation objects they allow you
to control the scope of the function call and each of its arguments
independently.
do(...)do_(...)
The return value of the call.
A function to call and list(s) of arguments to pass. All
should be quotation or dots objects, except the first
argument for do which is quoted literally.
For do_ all arguments should be quotation or dots objects, or
convertible to such using as.quo(). They will be concatenated
together by c.dots to form the call list (a dots object).
For do the first argument is quoted literally, but the
rest of the arguments are evaluated the same way as do_.
The head, or first element of the call list, represents the function, and it should evaluate to a function object. The rest of the call list is used as that function's arguments.
When a quotation is used as the first element, the call is evaluated
from the environment given in that quotation. This means that calls
to caller() (or parent.frame()) from within that function
should return that environment.
do is intended to be a replacement for base function do.call.
For instance these two lines are similar in effect:
do.call("complex", list(imaginary = 1:3))
do(complex, dots(imaginary = 1:3))
As are all these:
do.call("f", list(as.name("A")), envir = env)
do_(quo(f, env), quo(A, env)):
do_(dots_(list(as.name("f"), as.name("A")), env))
do_(dots_(alist(f, A), env))
get_call do.call match.call set_