I would like to have the option of specifying very precisely (exactly, if possible) the behavior of functions. For example,
foo <- function() {}
Env <- new.env(parent=emptyenv())
environment(foo) <- Env
foo()
# Error in { : could not find function "{"
Env$`{` <- base::`{`
environment(foo) <- Env
foo()
# NULL
I know I need to set the environment of foo, and that whatever foo depends upon is defined in that environment (or that environment's parent, or the parent's parent, etc.). But
- what all must be specified, and
- what can't be specified (i.e., in what cases am I stuck with default behavior)?
For example, in the following, why is there no error when the call to bar is attempted, when I leave " undefined (what kind of a thing is ", anyway? Or is it ""?).
bar <- function() {""}
Env <- new.env(parent=emptyenv())
Env$`{` <- base::`{`
environment(bar) <- Env
bar()
# [1] ""
My larger exercise is exploring ways to build very large systems with lots of dependencies, but no circular dependencies. I think I will need precise control over function environments in order to guarantee that there are no cycles. I am aiming for a ball of mud of sorts, where I can, given certain discipline, put all the R code I ever write into a single structure (which might not all be in memory, or even on local storage)—and, whenever I write new code, have the option of depending on some code I wrote in the past, provided that I have access to that ealier code.
Related posts include: [distinct], [specify], and [environments-enclosures-frames].
