Which are you comparing to? They are quite specialised, and are probably expensive as far as control operators go, but delimited continuations beat undelimited

Which are you comparing to? They are quite specialised, and are probably expensive as far as control operators go, but delimited continuations beat undelimited continuations every day of the week. I remember benchmarking the coroutine generator from srfi-125 (??), and already for the simplest case the delimited continuations in guile (compared to the undelimited ones in the reference implementation) were about 3x faster.