Moritz: Looks like you're raising the same concern as in here: https://ghc.haskell.org/trac/ghc/ticket/13124 Long story short: You cannot encode -0.0 directly. You have to represent it as an expression, multiplying `-1` with `fromRational 0`. Similar concerns apply to NaN and Infinity as well, though those cannot be written as literals to start with, so it isn't a big issue there. -Levent. On Sun, Sep 17, 2017 at 7:02 AM, Moritz Angermann < moritz.angermann@gmail.com> wrote:
Hi *,
I just ran into the following case:
fromRat (-0 :: Rational) :: Double 0.0
-0 :: Rational 0 % 1
How do I encode negative zero as a rational? The question come up as `CmmFloat` is defined as `CmmFloat Rational Width` in compiler/cmm/CmmExpr.hs. And my code generator thus turned (Int, Rational) into a floating point expression, and when trying to turn it into a `double` value, I ended up getting bad negative zeros.
This makes me believe I can’t actually encode `-0` as a Rational, and such `CmmFloat` will never contain `-0`?
Cheers, Moritz _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs