One more: really advanced type-checking. I've been using Haskell a bunch lately, and I've found that by the time the compiler stops snarling and hissing at me,

One more: really advanced type-checking. I've been using Haskell a bunch lately, and I've found that by the time the compiler stops snarling and hissing at me, most of the stupid little bugs are gone. That's a nice thing sometimes, even if appeasing the type system can be annoying.