Real World Haskell - 第3章 Part7 Reporting errors

Real World Haskell で Haskell を継続的に勉強中。

Defining Types, Streamlining Functions

Chapter 3. Defining Types, Streamlining Functions

Reporting errors

• error :: String -> a
  • error の result type は常に正しい
  • error は abort する

mySecond :: [a] -> a

mySecond xs = if null (tail xs)
              then error "list too short"
              else head (tail xs)

参考