Haskell/Solutions/Variables and functions

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Exercises
Explain how GHCi evaluates quadruple 5. Define a function that subtracts 12 from half its argument.

quadruple x = double (double x)
quadruple 5 = double (double 5)
quadruple 5 = double 10
quadruple 5 = 20

let subtractHalf x = (half x) - 12

Exercises
Write a function to calculate the volume of a box. Approximately how many stones are the famous pyramids at Giza made up of? Use GHCi for your calculations.

let volumeBox w h d = w * h * d

let stones l | l==1 = 1 | otherwise = l*l + stones (l-1)

Exercises
Write a function to calculate the volume of a cylinder.

let volumeCylinder r h = h * area r