until -package:numeric-prelude -package:base-prelude -package:distribution-opensuse -package:utility-ht -package:base-compat -package:yesod-paginator -package:monad-loops -package:ghc-lib-parser -package:termonad -package:LambdaHack -package:faktory 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.