[Haskell-cafe] Correct parsers for bounded integral values

[Stefan Klinger]

Pierre Thierry (2025-Jul-21, excerpt):
> Well, IIUC, it conforms to the Haskell 98 specification.

Hm.  Maybe I keep missing something here.  After all it's beeing
pointed out repeatedly by you guys (and yes, I do listen), but I fail
to verify that claim.

I don't think the Haskell Spec really *requires* the `read` function
for a bounded integral type to wrap around.

Jeff Clites via Haskell-Cafe (2025-Jul-21, excerpt):
> I think you will find, though, that `read @Word8` is intended to
> match the behavior of `(fromInteger @Word8) . (read @Integer)`. At
> least, the `Int` case is specified in the Haskell Report (in the
> Prelude implementation).

Sorry, I cannot find this.  Would you have a URL and a line number for
me?  I'm really sorry my google-foo seems to be insufficient.

I have found in the 98 report [4], similar in 2010 [5]:

    The results of exceptional conditions (such as overflow or
    underflow) on the fixed-precision numeric types are undefined; an
    implementation may choose error (_|_, semantically), a truncated
    value, or a special value such as infinity, indefinite, etc.

So, not violating the report, but the implementation might choose to
do better.

Cheers
Stefan


[1]: https://mail.haskell.org/pipermail/haskell-cafe/2025-July/137156.html
[2]: https://mail.haskell.org/pipermail/haskell-cafe/2025-July/137155.html
[3]: https://mail.haskell.org/pipermail/haskell-cafe/2025-July/137162.html
[4]: https://www.haskell.org/onlinereport/basic.html#sect6.4
[5]: https://www.haskell.org/onlinereport/haskell2010/haskellch6.html#x13-1350006.4


--
Stefan Klinger, Ph.D. -- computer scientist              o/X
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