import qualified Filesystem.Path as F
import Filesystem.Path.CurrentOS (toText)
import Data.Either.Combinators (fromRight')
ghci> fromRight' . toText . F.concat . F.splitDirectories $ fromString "/opt/ghc"
"//opt/ghc"
*Main> fromString $ "/opt/ghc" :: FilePath
FilePath "/opt/ghc"
*Main> F.concat . F.splitDirectories . fromString $ "/opt/ghc"
FilePath "//opt/ghc"
(on my linux box)
or more simply: