Laws for Show and Read?

Carter Schonwald carter.schonwald at
Fri Jun 7 03:51:48 UTC 2019

@Sven Panne <svenpanne at> you are correct, and its definitely true
1) we dont have informative literals for +/- infity OR the bits in the nan.
and those are truely informative in debugging, as IEEE float and show/read

so i support and would like to improve that state of affairs myself! (eg my
slow motion ghc float ieee improvement stuff, most recently removing x87
support to make rounding deterministic for a change on x86 32 platform!)

On Wed, Jun 5, 2019 at 5:15 PM Sven Panne <svenpanne at> wrote:

> Am Mi., 5. Juni 2019 um 22:57 Uhr schrieb Bertram Felgenhauer via
> Libraries <libraries at>:
>> [...] It's true that extra information in NaNs is lost, but they all
>> behave
>> the same anyway...
> That's true for normal arithmetic with them, but wrong if you use e.g. an
> external library which encodes things into the sign bit/paylod of NaNs (see
> e.g. NaN tagging). In the latter case, "read . show" actively destroys
> necessary information.
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> Libraries at
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