rlang (version 0.1)

invoke: Invoke a function with a list of arguments

Description

Normally, you invoke a R function by typing arguments manually. A powerful alternative is to call a function with a list of arguments assembled programmatically. This is the purpose of invoke().

Usage

invoke(.fn, .args = list(), ..., .env = caller_env(), .bury = c(".fn",
  ""))

Arguments

.fn

A function to invoke. Can be a function object or the name of a function in scope of .env.

.args, ...

List of arguments (possibly named) to be passed to .fn.

.env

The environment in which to call .fn.

.bury

A character vector of length 2. The first string specifies which name should the function have in the call recorded in the evaluation stack. The second string specifies a prefix for the argument names. Set .bury to NULL if you prefer to inline the function and its arguments in the call.

Details

Technically, invoke() is basically a version of base::do.call() that creates cleaner call traces because it does not inline the function and the arguments in the call (see examples). To achieve this, invoke() creates a child environment of .env with .fn and all arguments bound to new symbols (see env_bury()). It then uses the same strategy as eval_bare() to evaluate with minimal noise.

Examples

# NOT RUN {
# invoke() has the same purpose as do.call():
invoke(paste, letters)

# But it creates much cleaner calls:
invoke(call_inspect, mtcars)

# and stacktraces:
fn <- function(...) sys.calls()
invoke(fn, list(mtcars))

# Compare to do.call():
do.call(call_inspect, mtcars)
do.call(fn, list(mtcars))


# Specify the function name either by supplying a string
# identifying the function (it should be visible in .env):
invoke("call_inspect", letters)

# Or by changing the .bury argument, with which you can also change
# the argument prefix:
invoke(call_inspect, mtcars, .bury = c("inspect!", "col"))
# }