until -package:numeric-prelude -package:streaming -package:yesod-paginator -package:numhask -package:ghc-lib-parser -package:hledger-web -is:exact -package:Cabal -package:prelude-compat -package:free 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.