Re: [Haskell-cafe] [ANN] FloatingHex: Hexadecimal floats (quasiquoter and pretty-printer)

Thanks Iavor.. I should've indeed done that, but instead I directly opened a GHC feature request: http://ghc.haskell.org/trac/ghc/ticket/13126. Old habits die hard. I've since turned it into a proper proposal: https://github.com/LeventErkok/ghc-proposals/blob/hexFloats/proposals/0000-h... However, I was *not* able to add the label "Under discussion" as suggested by the instructions in: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposal-submissi... I didn't see a way of doing that in the pull-request. Perhaps a guru can fix that? Thanks, -Levent. On Tue, Jan 17, 2017 at 11:38 AM, Iavor Diatchki wrote:

Nicely done! I agree that this would be much nicer to just implement directly in GHC (and eventually add to the standard). Would you like to write it up as GHC proposal?

Here is info on how to do that: https://github.com/ghc-proposals/ghc-proposals

-Iavor

On Sat, Jan 14, 2017 at 3:06 PM, Levent Erkok wrote:

...

Quick update: version 0.2 of FloatingHex is now on hackage ( http://hackage.haskell.org/package/FloatingHex) which fixes a few glitches and makes the pretty-printer compatible with C's %a modifier. This brings the support on par with that in C/C++. The quasi-quoter is called qf, and the pretty-printer is called showHFloat, following the naming of other float-printers already available.

On Sat, Jan 14, 2017 at 1:10 AM, Levent Erkok wrote:

...

FloatingHex (http://hackage.haskell.org/package/FloatingHex) is a simple package that implement hexadecimal notation for floating point numbers, as described in p57-58 of http://www.open-std.org/jtc 1/sc22/wg14/www/docs/n1256.pdf

The package provides a quasi-quoter for hexadecimal floats: hf, and a pretty-printer for floats to show them in this notation: showFFloat. (Note that the latter is not 100% compatible with C's %a modifier for printf, but it does render a faithful representation of its input.)

Hex-floats are useful as they allow writing floating-point constants without any loss of precision, while remaining human readable. For instance, the float 2 is written as 0x1p1. (With the quasiquoter, the syntax is [hf|0x1p1|].) This representation is to be preferred over decimal rendering where loss of precision can be a problem: Note that not all floating point numbers have a terminating decimal representation as currently required by the Haskell syntax.

It would be nice if Haskell itself allowed for such literals in the language specs itself, following the recent changes to other language standards. (Again, see p57-58 of http://www.open-std.org/jtc 1/sc22/wg14/www/docs/n1256.pdf for the new C standard.) In the mean time, I hope FloatingHex library will provide a workaround for the numerophilias amongst us.

Bug reports and improvements always welcome!

Cheers,

-Levent.

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