How to shoot your leg with lazy in Haskell

Haskell

This code compile and works fine:

take' :: Int -> [Int] -> [Int]
take' x [] = []
take' 0 xs = []
take' x (xx:xxs) = xx : take' (x-1) xxs

Until we try to run this code with some not expected x (with minus) it will crash by memory limit, and not immediately. Run this:

> take' (-5) [1 .. ]

And get the infinity list on your screen. However we can obtain this situation by add one guard expression:

take' :: Int -> [Int] -> [Int]
take' x [] = []
take' 0 xs = []
take' x (xx:xxs)
  | x <= 0 = []
  | otherwise = xx : take' (x-1) xxs

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