-- capitilization of the needles. The caller should be certain that if IgnoreCase
-- is passed, the needles are already lower case.
setSearcherCaseSensitivity :: CaseSensitivity -> Searcher v -> Searcher v
setSearcherCaseSensitivity case_ searcher = searcher{
    searcherCaseSensitive = case_
  }


-- | Return whether the haystack contains any of the needles.
-- Case sensitivity depends on the properties of the searcher