24 Oct
2001
24 Oct
'01
3:07 p.m.
On Wed, Oct 24, 2001 at 07:51:12AM -0700, Simon Peyton-Jones wrote:
The Report is (regrettably) silent about what the Integer instances for succ and pred should be, but they should definitely simply add 1 (resp subtract 1). They should emphatically not use the default methods. I will add something to that effect in 6.3.4. ... 3. Specify that succ and pred on numeric types just add/subtract 1 (subject to (2) above).
Can you write some code people can cut&paste for instance of Enum on ordered numeric types, just so this is crystal clear? You might even put in some bounds checking: succ x = let y = x+1 in if y > x then y else error "succ overflowed" --Dylan