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Is goto as powerful as comefrom?

I just wondered if the hated goto statement is as powerful as the comefrom statement? In my opinion they are probably equal in their capabilities but I am not entirely sure on that. Is there any formal proof that they are equally powerful (or not equally powerful)?

For any who never heard of it: comefrom is sort of a reversed goto:

    comefrom doom;
    WriteLine("I will never stop executing!");
doom:
Solution

  • comefrom is strictly more powerful than goto.

    Each program with goto can be mechanically transformed into an equivalent comefrom-only program, by, well, replacing each goto with a corresponding comefrom.

    The reverse is not true. This program has no goto-only equivalent:

      doom:

  comefrom doom;
  WriteLine("I will never stop executing!");
  goto doom;

  comefrom doom;
  WriteLine("Guess my time has come!");

    This program print the first phrase an unknown number of times, then the second phrase, and exit. This kind of non-determinism is not achievable with conventional programming languages that lack comefrom.