break/exit script

Perhaps you just want to stop executing a long script at some point. ie. like you want to hard code an exit() in C or Python.

print("this is the last message")
stop()
print("you should not see this")

Edited. Thanks to @Droplet, who found a way to make this work without the .Internal(): Here is a way to implement an exit() command in R.

exit <- function() { invokeRestart("abort") }    

print("this is the last message")
exit()
print("you should not see this")

Only lightly tested, but when I run this, I see this is the last message and then the script aborts without any error message.

Below is the uglier version from my original answer.

exit <- function() {
  .Internal(.invokeRestart(list(NULL, NULL), NULL))
}

You could use the stopifnot() function if you want the program to produce an error:

foo <- function(x) {
    stopifnot(x > 500)
    # rest of program
}

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