Hmm, too simple :-P ...Thanks Henning Thielemann wrote:

On Wed, 13 Apr 2005, Bo Herlin wrote:

...

Hi

How come

...

foldr1 min [(maxBound::Int) % 1,1 % 2]

2147483647 % 1

I guess that foldr1 min == minimum

...

but

...

foldr1 min [2147483647 % 1,1 % 2]

1 % 2

Why???

The first one certainly causes an overflow with machine word Ints whereas 2147483647 is an Integer and thus all other numbers are interpreted as Integers.

Yep, got it, Thanks! Cale Gibbard wrote:

Hmm... let a = (maxBound :: Int)%1 in 1 < a && a < 1/2 == True

...

From the Ord instance for Ratio a (x:%y) < (x':%y') = x * y' < x' * y

So the comparison for 1 < a looks like 1 * 1 < (maxBound :: Int) * 1 which is true. And the comparison for a < 1/2 looks like (maxBound :: Int) * 2 < 1 * 1 ==> -2 < 1 which is again true!

If you want well-behaved rationals, I suppose you have to use Ratio Integer.

Hope this helps, - Cale

On 4/13/05, Bo Herlin wrote:

...

Hi

How come

...

foldr1 min [(maxBound::Int) % 1,1 % 2] 2147483647 % 1

but

...

foldr1 min [2147483647 % 1,1 % 2] 1 % 2

Why???

/Bo Herlin _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe