[Haskell-cafe] Problem about pattern matching.

[Magicloud Magiclouds]

Hi, I have code as below. How come "case" version works wrong and
gives me "overlap" compiling warning? Thanks.
  if dayOfMonth == firstDayOfMonth
    then v day (x, y)
    else if dayOfMonth == lastDayOfMonth
      then not_ $ v day (x, y)
      else Mider day (x, y)

  case dayOfMonth of
    firstDayOfMonth -> v day (x, y)
    lastDay -> not_ $ v day (x, y)
    _ -> Mider day (x, y)
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