>>247
Haskellはそう言うのパターンマッチがあるんで楽。

main = mapM_ f [1..4]

f 1 = putStrLn "x = 1"
f 2 = putStrLn "x = 2"
f 3 = putStrLn "x = 3"
f x = putStrLn "x = others number"

output:

x = 1
x = 2
x = 3
x = others number