until -package:numeric-prelude -package:streaming -package:yesod-paginator -package:Cabal -package:rebase -package:foundation -package:elerea -package:util -package:basic-prelude -package:IfElse 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.