Haskell Report (again)

[Simon Peyton-Jones]

Dale is absolutely right!  How has this entirely bogus code survived so
long?

Here is an (alleged) fix, which works in the tests I've tried.  If
anyone
else can spare a moment to check my code I'd be very grateful.

This is definitely going in the Revised H98 report!

Thanks Dale.

Simon

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Library Report, Numeric library, Section 4.1, page 13.
  In the definition of formatRealFloat,=20
  in the definition of doFmt,
  in the FFFixed branch of "case fmt of ...",
  in the Nothing branch of "case  decs of ..."
  replace the entire branch "Nothing -> ..." with

       Nothing | e >=3D 0    -> take e (ds ++ repeat '0') ++ "." ++ mk0
(drop e ds)
	         | otherwise -> "0." ++ replicate (-e) '0' ++ ds

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D


| -----Original Message-----
| From: Dylan Thurston [mailto:dpt@math.harvard.edu]=20
| Sent: 17 July 2001 07:33
| To: Simon Peyton-Jones
| Cc: haskell@haskell.org
| Subject: Re: Haskell Report (again)
|=20
|=20
| On Tue, Jul 10, 2001 at 05:50:08AM -0700, Simon Peyton-Jones wrote:
| > As ever, the draft is at
| >=20
| > 	http://research.microsoft.com/~simonpj/haskell98-revised
| >=20
| > I'm really hoping this is the final version, but experience=20
| suggests=20
| > that whenever I say that someone discovers an entirely new=20
| question!=20
| > So I'm putting it out again for you to pick over.
|=20
| I'm astonished no one has noticed this before, but in the=20
| library report for the Numeric library, the definition of=20
| showFFloat is buggy:
|=20
| showFFloat Nothing 0.02 ""
|=20
| goes into an infinite loop.  (There is an auxiliary function
| 'f n s ds' which does not consider the case n < 0).
|=20
| This suggests that there needs to be a code review of=20
| formatRealFloat, which I have not yet done.
|=20
| --Dylan Thurston
|=20