users/aspen/xanthous/src/Xanthous/Util/Optparse.hs


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module Xanthous.Util.Optparse
  ( readWithGuard
  ) where
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import Xanthous.Prelude
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import qualified Options.Applicative as Opt
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readWithGuard
  :: Read b
  => (b -> Bool)
  -> (b -> String)
  -> Opt.ReadM b
readWithGuard predicate errmsg = do
  res <- Opt.auto
  unless (predicate res)
    $ Opt.readerError
    $ errmsg res
  pure res