until -package:numeric-prelude -package:base-prelude -package:hosc -package:numhask -package:extra -package:prelude-compat -package:yesod-paginator -package:elerea -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.