[Haskell-cafe] lexicographic order

[Chaddaï Fouché]

2008/3/31, Simeon Mattes <simeon.mattes at gmail.com>:
> why I should take as right
>
> (a,b) <= (a',b') iff (a < a' or (a == a' and b <= b'))
>
> and not
>
> (a,b) <= (a',b') iff (a <= a' or (a == a' and b <= b'))
>
>
> The latter seems more logical, doesn't it?

No, it doesn't, since in the latter (1,2) <= (1,1) because 1 <= 1

> Though I can't understand why both
> (Branch l r) <= (Branch l' r')  =  l < l' || l == l' && r <= r'
> (Branch l r) <= (Branch l' r')  =  l <= l' || l == l' && r <= r'
> give the same results

They don't, the second is a mistake, the first is the right one.

-- 
Jedaï