I think this is a mistake, yes. They should not raise such exceptions, but rather just wrap around—minBound `quot` (-1) should be -minBound=minBound. That would justify the behavior of rem and mod, and makes much more sense than the current behavior for Int as a ring. On Jun 1, 2015 12:41 PM, "Nikita Karetnikov" <nik...@karetnikov.org> wrote:
> According to the documentation, rem and mod must satisfy the following > laws: > > -- > (x `quot` y)*y + (x `rem` y) == x > rem > > -- > (x `div` y)*y + (x `mod` y) == x > mod > > https://hackage.haskell.org/package/base-4.8.0.0/docs/src/GHC-Real.html > > Note, however, that there is a case when quot and div result in an > arithmetic overflow: > > Prelude> (minBound :: Int) `quot` (-1) > *** Exception: arithmetic overflow > Prelude> (minBound :: Int) `div` (-1) > *** Exception: arithmetic overflow > > while rem and mod don't: > > Prelude> (minBound :: Int) `rem` (-1) > 0 > Prelude> (minBound :: Int) `mod` (-1) > 0 > > Is this a mistake? > > For the record, I'm aware of the safeint package, which raises the error > for rem and mod, and this ticket: > > https://ghc.haskell.org/trac/ghc/ticket/8695 > _______________________________________________ > Glasgow-haskell-users mailing list > Glasgow-haskell-users@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users >
_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users