Hi Clark,

ghci is defaulting to Integer
modexp2 forces Int
Int overflows with 3^40

On 31/05/12 17:35, Clark Gaebel wrote:

*X>  3^40 `mod` 3 == modexp2 3 40 3
False

*X> fromInteger (3^40 `mod` 3) == modexp2 3 40 3
True

*X>  modexp2 3 40 3
0
*X>  3^40 `mod` 3
0

*X> 3^40 `mod` 3 ::Int

2

I'm confused. Last I checked, 0 == 0.

Int overflow is ugly!

*X> 3^40
12157665459056928801
*X> maxBound :: Int
9223372036854775807


Claude

Using GHC 7.4.1, and the file x.hs (which has been loaded in ghci) can be
found here: http://hpaste.org/69342

I noticed this after prop_sanemodexp was failing.

Any help would be appreciated,
  - Clark

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