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Composition operator

composition operator is “.”
type: (b → c) → (a → b) → a → c
takes two functions as parameter and combines the functions
- first function is applied to the result of the second function

example:

import qualified Data.Char as Ch (ord)
 
main :: IO ()
main = 
    do
        print $ f3 'a'
        print $ f4 'a'
 
f1 :: Char -> Integer
f1 ch = toInteger $ Ch.ord(ch)
 
f2 :: Integer -> (Integer, Double)
f2 n = (n, fromIntegral n :: Double)
 
f3 :: Char -> (Integer, Double)
f3 = f2 . f1
 
f4 :: Char -> (Integer, Double)
f4 ch = f2 (f1 ch)

executes with output:
```
(97,97.0)
(97,97.0)
```

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