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40-blitz-einfhrung-in-die-funktionale-programmierung.hs

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+module Intro where
+
+
+-- Ein Haustier ist eins der folgenden:
+-- - Hund -ODER-
+-- - Katze -ODER-
+-- - Schlange
+-- Fallunterscheidung
+data Pet -- neuer Datentyp
+    = Dog -- Fall
+    | Cat
+    | Snake
+    deriving Show
+
+-- Ist ein Haustier niedlich?
+isCute :: Pet -> Bool
+isCute Dog = True
+isCute Cat = True
+isCute Snake = False
+
+-- Tier (auf dem texanischen Highway) ist eins der folgenden:
+-- - Gürteltier -ODER-
+-- - Papagei
+
+-- Ein Gürteltier hat folgende Eigenschaften:
+-- - (tot -ODER- lebendig) -UND-
+-- - Gewicht
+-- zusammengesetzte Daten
+
+-- Papagei hat folgende Eigenschafen:
+-- - Satz -UND-
+-- - Gewicht
+
+data Liveness
+    = Dead 
+    | Alive
+    deriving Show
+
+type Weight = Double
+
+data Animal
+    = Dillo { dilloLiveness :: Liveness, dilloWeight :: Weight  } -- "Record"
+    | Parrot { parrotSentence :: String, parrotWeight :: Weight }
+    deriving Show
+
+dillo1 = Dillo { dilloLiveness = Alive, dilloWeight = 10 }
+dillo2 = Dillo { dilloLiveness = Dead, dilloWeight = 8}
+parrot1 = Parrot { parrotSentence = "Hallo Tuebix", parrotWeight = 1 }
+
+runOver :: Animal -> Animal
+runOver (Dillo { dilloWeight = w }) =
+    Dillo { dilloLiveness = Dead, dilloWeight = w }
+runOver (Parrot { parrotSentence = s, parrotWeight = w }) =
+    Parrot { parrotSentence = "", parrotWeight = w }
+
+
+{-
+interface Animal {
+    void runOver()
+}
+class Dillo implements Animal {
+  Liveness liveness;
+  Weight weight;
+
+   void runOver() { 
+    self.liveness = Dead;
+  }
+}
+
+class Parrot implements Animal {
+
+} 
+-}
+
+-- Effekte
+-- - I/O
+-- - Zustand
+-- - Exceptions
+
+-- I/O-behafteter Ablauf mit Ergebnis a: IO a
+-- main :: IO ()
+
+-- Kombinatormodelle
+
+
+-- Seife
+-- Shampoo
+-- Duschgel, bestehend aus Seife und Shampoo
+
+data Hairtype = Normal | Oily | Dandruff
+  deriving (Show)
+
+data ShowerProduct =
+    Soap { soapPh :: Double }
+  | Shampoo { shampooHairtype :: Hairtype }
+  | ShowerGel ShowerProduct ShowerProduct -- Kombinator
+--            ^^^^^^^^^^^^^ Selbstreferenz
+  deriving Show
+
+soap1 = Soap { soapPh = 7 }
+shampoo1 = Shampoo { shampooHairtype = Oily }
+showergel1 = ShowerGel soap1 shampoo1
+showergel2 = ShowerGel showergel1 soap1
+
+soapProportion :: ShowerProduct -> Double -- zwischen 0 und 1
+soapProportion (Soap {}) = 1
+soapProportion (Shampoo {}) = 0 
+soapProportion (ShowerGel product1 product2) =
+    (soapProportion product1 + soapProportion product2) / 2
+
+{-
+- einfaches Beispiel
+Zero-Coupon Bond
+"Ich bekomme 24.12. 100€."
+
+- "atomare Bestandteile / Ideen" zerlegen
+  - Währung
+  - Betrag
+  - Datum / später
+
+- Wiederholen
+
+FX Swap:
+- Weihnachten bekomme ich 100€ und zahle $100.
+-}
+
+data Date = Date String
+  deriving Show
+type Amount = Double
+data Currency = EUR | GBP | USD
+  deriving Show
+{-
+data Contract =
+    ZeroCouponBond Date Amount Currency
+    deriving Show
+
+zcb1 = ZeroCouponBond (Date "2023-12-24") 100 EUR
+-}
+
+data Contract =
+    -- "1€ jetzt"
+    One Currency
+    -- "100€ jetzt"
+  | Multiple Amount Contract
+  | Delay Date Contract
+  | Invert Contract
+  | And Contract Contract
+  | Zero
+  deriving Show
+
+c1 = One EUR
+-- 100€ jetzt
+c2 = Multiple 100 (One EUR)
+
+zcb1 = Delay (Date "2023-12-14") (Multiple 100 (One EUR))
+
+zeroCouponBond date amount currency =
+    Delay date (Multiple amount (One currency))
+
+zcb1' = zeroCouponBond (Date "2023-12-24") 100 EUR