Antoine Latter wrote:

To recover from my overly complex previous post, here is a much simply goto based on existing monad transformers:

...

goto :: Monad m => ContT r m r -> ContT r m a goto (ContT m) = ContT $ \_ -> m return

That is precisely how continuations were discovered (as John Reynolds documents, continuations have been discovered and rediscovered multiple times). The paper Continuations: A Mathematical Semantics for Handling Full Jumps Christopher Strachey and Christopher P. Wadsworth http://www.ling.ohio-state.edu/research/groups/commies/past/autumn2009/strac... first published in 1974 and republished in Higher-Order and Symbolic Computation, 13, 135-152, 2000 starts with the following sentence: The purpose of this paper is to explain a method of giving the mathematical semantics of a programming language which includes a very general form of jump (goto statement). The cited goto expression above appears, in mathematical notation, as the second equation on p. 143 of the paper. Labels are considered next. The paper is still a good read. One can literally implement the language of the paper, by reading domain equations as the implementation of a monad. Incidentally, Note 1 of the paper anticipated delimited continuations.