On Wed, Aug 27, 2008 at 3:19 AM, Henning Thielemann
On Tue, 26 Aug 2008, John Meacham wrote:
But is also makes the functions less useful and another source of non-completeness. I certainly always considered accepting negative numbers a feature of those functions and not an infelicity. Sometimes you want 'drop 1 xs' and other times you want 'tail xs' (or equivalent).
It's very confusing for readers of your programs, if you use 'drop 1' instead of 'tail'. The names 'drop' and 'tail' don't give the reader a hint, that 'drop' works for empty lists and 'tail' doesn't. 'drop 1' and 'tail' should behave identically for empty lists and a function with different behaviour should have a different name.
Personally, I'd prefer to see tail dropped from the Prelude (not any time soon, of course). The fewer incomplete functions are in the Prelude, the better, and drop has very nice and easy-to-understand behavior. Folks who want to crash on empty lists should write their own or use pattern matching. David