27 Mar
2009
27 Mar
'09
5:51 p.m.
2009/03/27 John Lato
From: Jules Bean
wren ng thornton wrote:
The type of head should not be [a] -> a + Error, it should be (a:[a]) -> a. With the latter type the compiler can ensure the precondition will be proved before calling head, thus eliminating erroneous calls.
Yes, but you know and I know that's not haskell.
I'm talking about haskell.
In haskell - a language which does not fully support dependent types - head is both necessary and useful.
I could follow the rest of this, but I don't understand why 'head' is necessary. Couldn't you always replace it with a case statement, with undefined on [] if necessary?
How would that be any different from head? -- Jason Dusek