sample usage for lazy pattern matching

gistfile1.hs

module Main where

fetch :: [Int] -> Int
fetch args =
  let
    (n : ~(a : ~(b : ~(c : x)))) = args
  in
    if n == 1
      then a
      else if n == 2
      then a + b
      else a + b + c

main = do
  putStrLn $ show (fetch [1, 5])
  putStrLn $ show (fetch [2, 5, 10])
  putStrLn $ show (fetch [3, 5, 10, 15])