Gibt es in Haskell etwas Ähnliches wie Unterwächter?

Ich schreibe ein Programm zur Klassifizierung musikalischer Intervalle. Die konzeptionelle Struktur ist ziemlich kompliziert und ich würde sie so klar wie möglich darstellen. Die ersten Codezeilen sind ein kleiner Auszug, der ordnungsgemäß funktioniert. Der zweite ist der Pseudocode, der meine Anforderungen an die Prägnanz erfüllen würde.

interval pt1 pt2
  | gd == 0 && sd <  (-2) = ("unison",show (abs sd) ++ "d") 
  | gd == 0 && sd == (-2) = ("unison","dd")
  | gd == 0 && sd == (-1) = ("unison","d")
  | gd == 0 && sd == 0    = ("unison","P")
  | gd == 0 && sd == 1    = ("unison","A")
  | gd == 0 && sd == 2    = ("unison","AA")
  | gd == 0 && sd >  2    = ("unison",show sd ++ "A")

  | gd == 1 && sd <  (-1) = ("second",show (abs sd) ++ "d")
  | gd == 1 && sd == (-1) = ("second","dd")
  | gd == 1 && sd == 0    = ("second","d")
  | gd == 1 && sd == 1    = ("second","m")
  | gd == 1 && sd == 2    = ("second","M")
  | gd == 1 && sd == 3    = ("second","A")
  | gd == 1 && sd == 4    = ("second","AA")
  | gd == 1 && sd >  4    = ("second",show (abs sd) ++ "A")

  where
  (bn1,acc1,oct1) = parsePitch pt1
  (bn2,acc2,oct2) = parsePitch pt2
  direction = signum sd
  sd = displacementInSemitonesOfPitches pt1 pt2
  gd = abs $ displacementBetweenTwoBaseNotes direction bn1 bn2

Gibt es eine Programmierstruktur, die Vereinfache den Code wie der folgende Pseudocode?

interval pt1 pt2 
  | gd == 0  | sd <  (-2) = ("unison",show (abs sd) ++ "d") 
             | sd == (-2) = ("unison","dd")
             | sd == (-1) = ("unison","d")
             | sd == 0    = ("unison","P")
             | sd == 1    = ("unison","A")
             | sd == 2    = ("unison","AA")
             | sd >  2    = ("unison",show sd ++ "A")  
  | gd == 1  | sd <  (-1) = ("second",show (abs sd) ++ "d")
             | sd == (-1) = ("second","dd")
             | sd == 0    = ("second","d")
             | sd == 1    = ("second","m")
             | sd == 2    = ("second","M")
             | sd == 3    = ("second","A")
             | sd == 4    = ("second","AA")
             | sd >  4    = ("second",show (abs sd) ++ "A")
  | gd == 2  | sd ...     = ...
             | sd ...     = ...
  ...
  | mod gd 7 == 1 | mod sd 12 == ...
                  | mod sd 12 == ...
  ...
  | otherwise = ...

  where
  (bn1,acc1,oct1) = parsePitch pt1
  (bn2,acc2,oct2) = parsePitch pt2
  direction = signum sd
  sd = displacementInSemitonesOfPitches pt1 pt2
  gd = abs $ displacementBetweenTwoBaseNotes direction bn1 bn2

ielen Dank im Voraus für Ihre Vorschläg

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