Coroutines rely on "pausable" workalikes for control flow functions
like if, while, and so on. pausables() scans for and returns
a list of all pausable functions visible from the present
environment.
pausables(envir = caller(), packages = NULL)A list of expressions (either names or ::: calls)
The environment to search (defaulting to the calling environment).
By default, will only look for pausable functions
visible from the caller's environment. packages argument
additionally specifies aditional packages to
search. packages=base::.packages() will search all currently
loaded packages. [.packages(all.available=TRUE)] will search
all installped package.
A pausable function is a public function that has a corresponding
private function with a name endng with _cps. Most of these
private functions are defined in async source file cps.r. For
instance, async:::for_cps contains the pausable implementation of
for.