X-Git-Url: http://gitweb.michael.orlitzky.com/?p=dead%2Fhtsn-import.git;a=blobdiff_plain;f=src%2FMisc.hs;fp=src%2FMisc.hs;h=cb992c78c7ade99443c2076b35d777247414b9a0;hp=0000000000000000000000000000000000000000;hb=fdd85d5ed7944e6a6373c99c2e341f370cd931f8;hpb=073bbfba4165d4c01d29daaa7523c35c6cc7d114

diff --git a/src/Misc.hs b/src/Misc.hs
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+-- | Miscellaneous utility functions
+module Misc (
+  double_just )
+where
+
+-- | If given 'Nothing', return 'Nothing'. Otherwise wrap our argument
+--   in another 'Just'. This is used when handling optional XML
+--   elements that are optionally empty. If the element is missing, we
+--   want 'Nothing'. And if the contents are missing, we want
+--   'Nothing' then too. But if something is present, we need @Just
+--   (Just foo)@ for the types to match up.
+--
+--   ==== __Examples__:
+--
+--   >>> double_just Nothing
+--   Nothing
+--   >>> double_just (Just 2)
+--   Just (Just 2)
+--
+double_just :: (Maybe a) -> Maybe (Maybe a)
+double_just val =
+  case val of
+    Nothing -> Nothing
+    just_something -> Just just_something