learning_haskell1

lhs.hs

module Lib
    ( someFunc
    ) where

someFunc :: IO ()
someFunc = putStrLn "someFunc"

lucky :: (Integral a) => a -> String
lucky 7 = "Lucky NUMBER Se7e"
lucky x = "Sorry, you're out of luck, pal!"

data Expr = Var String
            | Lit Integer
            | Expr :+: Expr
            | Expr :-: Expr
            | Expr :*: Expr deriving (Show, Eq)

factorial :: (Integral a) => a -> a
factorial 0 = 1
factorial n = n * factorial(n - 1)

addVectors :: (Num a) => (a, a) -> (a, a) -> (a, a)
addVectors (x1, y1) (x2, y2) = (x1 + x2, y1 + y2)

first :: (a, b, c) -> a
first (x, _, _) = x

second :: (a, b, c) -> b
second (_, y, _) = y

third :: (a, b, c) -> c
third (_, _, z) = z

head' :: [a] -> a
head' [] = error "Can't call head on an empty list, dummy!"
head' (x:_) = x

firstTwo' :: [a] -> (a, a)
firstTwo' (x:y:_) = (x, y)
firstTwo' [] = error "Can't call firstTwo' on this list, dummy!"

firstThree' :: [a] -> (a, a, a)
firstThree' (x:y:z:_) = (x, y, z)
firstThree' [] = error "Can't call firstThree' on this list, dummy!"

length' :: (Num b) => [a] -> b
length' [] = 0
length' (_:xs) = 1 + length' xs

doBinary :: (Eq a, Ord a) => [a] -> Int
doBinary [] = error "Can't search on an empty list"