Stop function evaluation using another function in R

Question

I did a test with nested return function in R, but without success. I came from Mathematica, where this code works well. Here is a toy code:

fstop <- function(x){
  if(x>0) return(return("Positive Number"))
}

f <- function(x){
  fstop(x)
  "Negative or Zero Number"
}

If I evaluate f(1), I get:

[1] "Negative or Zero Number"

When I expected just:

[1] "Positive Number"

The question is: there is some non-standard evaluation I can do in fstop, so I can have just fstop result, without change f function?

PS: I know I can put the if direct inside f, but in my real case the structure is not so simple, and this structure would make my code simpler.

Answer 1

Going to stick my neck out and say...

No.

Making a function return not to its caller but to its caller's caller would involve changing its execution context. This is how things like return and other control-flow things are implemented in the source. See:

https://github.com/wch/r-source/blob/trunk/src/main/context.c

Now, I don't think R level code has access to execution contexts like this. Maybe you could write some C level code that could do it, but its not clear. You could always write a do_return_return function in the style of do_return in eval.c and build a custom version of R... Its not worth it.

So the answer is most likely "no".