until -package:numeric-prelude -package:util -package:hedgehog -package:yesod-paginator -package:intro -package:extra -package:streaming -package:scalpel-core -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.