until -package:numeric-prelude -package:streaming -package:util -package:snap-core -package:selective -package:singletons-base -package:linear-base -package:classy-prelude -package:xmonad-contrib -package:netwire -package:ghc package:dunai
Similar to Yampa's delayed switching. Loses a b in case of an
exception.
Run the first
msf until the second one produces
True
from the output of the first.