[racket-dev] [racket] Question about round

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Fri Sep 30 14:01:30 EDT 2011

Vincent's proposal seemed to me to be just a renaming the current
functions. Is there an intended change to the numeric tower that I'm
missing?

At Fri, 30 Sep 2011 13:28:12 -0400, Matthias Felleisen wrote:
> 
> I sent this to Matthew privately but I think we need to be
> much more careful with 'interesting'. While you are right 
> about the 'wired into our code' part, I think the two of 
> you are wrong about the 'interesting' part. 
> 
> From a type perspective, the numeric tower comes with major
> flaws and it would be wonderful if a language that divorces
> itself from the old flawed Scheme world could make a clean
> cut and do better. 
> 
> But I am also the person who preaches 'the path from here to
> there' and agree that the 'wired' argument for the existing
> code base and outside consumers tells us that Racket isn't 
> the language that can fix these mistakes. 
> 
> 
> 
> 
> On Sep 30, 2011, at 12:32 PM, Robby Findler wrote:
> 
> > This is my opinion, too.
> > 
> > Robby
> > 
> > On Fri, Sep 30, 2011 at 11:20 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> >> I think this is a good change for the next language, but not for `#lang
> >> racket'.
> >> 
> >> As confusing as the current `integer?' may be, I think its definition
> >> is deeply wired into our code, tests, and documentation. I may guess
> >> wrong, but my best estimate of the hassle for this change is that it's
> >> too much trouble for too little payoff, and we could spend our energy
> >> on more interesting things.
> >> 
> >> At Fri, 30 Sep 2011 11:59:25 -0400, Vincent St-Amour wrote:
> >>> On a more general note, do we really need inexact integers?
> >>> 
> >>> The behavior of `integer?' is confusing, and I don't see especially
> >>> compelling reasons to keep it this way. The subject comes up every
> >>> couple of months on the mailing list, so we should do something about it.
> >>> 
> >>> Here's a proposal:
> >>> `integer?' becomes the same as `exact-integer?' (which is kept for
> >>> backwards compatibility).
> >>> `positive-integer?' and `nonnegative-integer?' are added as
> >>> equivalents to their `exact' counterparts.
> >>> `inexact-integer?' is added, to cover for the use case of checking is
> >>> an inexact number has been rounded.
> >>> 
> >>> I volunteer to implement this if we agree that this is the right
> >>> thing.
> >>> 
> >>> Vincent
> >>> 
> >>> 
> >>> 
> >>> At Fri, 30 Sep 2011 07:16:22 -0600,
> >>> Doug Williams wrote:
> >>>> 
> >>>> Another such annoyance is than (min 1 +inf.0) => 1.0 - because if any
> >>>> argument is inexact, the result is inexact. I don't think this makes sense
> >>>> in the case of infinities. Infinities are very useful as initial values 
> for
> >>>> things that are being minimized or maximized, but there is always the need
> >>>> for inexact->exact to protect against the (unexpected) coercion.
> >>>> 
> >>>> This is all from the original R5RS and continued in R6RS - but, we aren't
> >>>> that language.
> >>>> 
> >>>> Could we get an exception to the coercions in the case of +/-inf.0? Or an
> >>>> alternative min/max that don't do it?
> >>>> 
> >>>> On Fri, Sep 30, 2011 at 6:53 AM, Matthias Felleisen
> >>> <matthias at ccs.neu.edu>wrote:
> >>>> 
> >>>>> 
> >>>>> exact-round is preferred.
> >>>>> 
> >>>>> 
> >>>>> 
> >>>>> On Sep 30, 2011, at 8:51 AM, Eli Barzilay wrote:
> >>>>> 
> >>>>>> Yesterday, Ryan Culpepper wrote:
> >>>>>>> The pragmatic answer is you generally have to write
> >>>>>>> 
> >>>>>>>   (inexact->exact (round x))
> >>>>>>> 
> >>>>>>> which is annoying, but no one has yet bothered to add a standard
> >>>>>>> library function for this, as far as I know.
> >>>>>> 
> >>>>>> [From the annoyed side, especially since that thing tends to come in
> >>>>>> bunches which can make some quick code look much heavier than it is:]
> >>>>>> 
> >>>>>> Maybe it's time to add something for that?  `eround'?  (But even
> >>>>>> `exact-round' would be better than the above.)
> >>>>>> 
> >>>>>> --
> >>>>>>          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
> >>>>>>                    http://barzilay.org/                   Maze is Life!
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