[Haskell-beginners] HXT and missing or null values

[Ian Knopke]

I got it. For anyone else running into the problem from my earlier
email, the way to get a null string is as follows:

Replace this line:
second <- text <<< atTag "second" -< x

with this:
second <- ((text `orElse` (constA "")) <<< atTag "second" -< x


Fixed program:

data Thing = Thing {first :: String, second :: String}

getThings = atTag "thing" >>>
  proc x -> do
      first     <- text <<< atTag "first" -< x
      second <- ((text `orElse` (constA "")) <<< atTag "second" -< x

      returnA -< Thing {first = first,second = second}

atTag tag = deep (isElem >>> hasName tag)

text = getChildren >>> getText

parseThings str = runX (readString [withValidate no] str >>> getThings)