The nice thing about infinite loops, `undefined` and `error "foo"` is that nothing can use their result (i.e. nothing happens "after", although that's a tricky

The nice thing about infinite loops, `undefined` and `error "foo"` is that nothing can use their result (i.e. nothing happens "after", although that's a tricky concept with lazy evaluation!) In other words, Haskell doesn't have try/catch for things like `undefined`, so we do have to worry about them occuring, but we don't have to worry about them causing the code to misbehave; it'll either behave or it will stop progressing (either halting or looping infinitely). On the other hand, the "IO" DSL built in to Haskell can do try/catch; but once you're in IO, all bets are off.