until -package:numeric-prelude -package:streaming -package:util -package:snap-core -package:utility-ht -package:llvm-hs-pure -package:extra -package:Cabal-syntax -package:base 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.