如何在R中检查函数是否匿名

Question

I want to write a function that distinguishes if a function is being sourced from a package or set up anonymously in a case where these are the only 2 possibilities (constraints of a one-liner).

If it's the latter - let's call it a variable anonymous.function - I'd want to 'get it out' of the (function(parameters){inner_workings}) closure as function(){} by eval(parse(text = call(anonymous.function()))

• typeof(package::function) returns "closure"
• typeof((function(parameters) {inner_workings})) likewise returns "closure"

Should I distinguish the two by comparing environment , or namespace ?

• environment(package::function) returns <environment: namespace:package>
• environment((function)parameters) {inner_workings})) returns <environment: R_GlobalEnv>

I'm hesitant to say that I'll only assume it's anonymous if environment is GlobalEnv, as the stack could be traversed below Global if I understand correctly in some situations, eg if I'm running this function within a function, so I'd check if environment is a namespace.

Can anyone tell me how I can check for a namespace? I can see it in the reported string as <environment: namespace:...> but can't seem to access that distinction. The only distinction I can see is that a namespace environment isn't hashed - that's only observed upon failing to run env.profile() for an unhashed environment...

Surely there's a simple way to check for anonymous functions without a try/catch statement! :-) Advice would be greatly appreciated, the R documentation seems to run dry at this level.

Edit ideally accessing the data structure, ie without grepl ing a string!

Answer 1

Does packageName work for you? I was unsure about the desired output of a function like f1 <- mean . See below for my version.

is_package_fun <- function(fun) 
  !is.null(packageName(environment(fun)))

# defining functions
f1 <- mean
f2 <- function(x) mean(x)

# checking
is_package_fun(mean)
## [1] TRUE
is_package_fun(f1) # not sure about desired output...
## [1] TRUE
is_package_fun(f2)
## [1] FALSE