Bangs are well written and idiomatic Haskell code. Haskell is a default-lazy language. Good code uses lazy algorithms (to avoid wasted work) and strict data st

Bangs are well written and idiomatic Haskell code. Haskell is a default-lazy language. Good code uses lazy algorithms (to avoid wasted work) and strict data structures (to avoid space leaks), so efficient data structures need the bangs.