[plt-scheme] Question about science collection / histogram

Vincent,

I updated the science collection in PLaneT to V2.9 to fix the problem with
histograms.  I will do a more thorough search of the code to see if I have
the same construct elsewhere.  Thanks for finding the problem and I
apologize for the inconvenience.  I've also updated the subversion
repository on Schematics with the changes.

Let me know if you still have a problem.

Doug

On Mon, Jan 28, 2008 at 4:00 PM, Doug Williams <m.douglas.williams at gmail.com>
wrote:

> Actually, it does bring up an interesting question.  My contract for
> histogram-increments says it returns void?.  The above code worked at some
> point in the past.  And, adding (void) as the return value for the outer let
> makes it work again.  I assume that takes the (exit) call that is bombing
> out of the tail position, which was somehow causing the problem. Is that a
> correct guess?
>
> If so, does this mean I can't terminate the loop (returning nothing) with
> a continuation call?
>
> Just trying to understand the actual problem I have.  I will add the
> explicit (void) call to fix it.
>
> Doug
>
>
> On Mon, Jan 28, 2008 at 3:34 PM, Doug Williams <
> m.douglas.williams at gmail.com> wrote:
>
> > It looks like sloppy code on my part.  I assume it worked in some
> > previous version, but I will change the exit call to take an argument.  I
> > assume something downstream wants a value now.  I'll release a new version
> > this evening.
> >
> > Doug
> >
> >
> > On Mon, Jan 28, 2008 at 3:20 PM, Vincent Rayappa <vrayappa at gmail.com>
> > wrote:
> >
> > > I would like to use the histogram module of the science collection to
> > > generate histograms with custom ranges.
> > >
> > > I tried:
> > >
> > > (define h1 (make-histogram 4))
> > > (set-histogram-ranges! h '#(0.0 1.0 2.0 4.0 16.0))
> > >
> > > So far so good, but when I try to add a value like this:
> > >
> > > (histogram-increment! h 5)
> > >
> > > I get this error:
> > >
> > > context expected 1 value, received 0 values
> > > .../histogram.ss:219:10: (call/ec (lambda (exit) (if (< x (....))
> > > (exit)) ((letrec-values ((....)) doloop) 0)))
> > > [unknown source]: (void?31 (val (histogram?29 histogram?27) (real?30
> > > real?28)))
> > >
> > > Any idea what is going on?
> > >
> > > The function is defined like this:
> > >
> > >  ;; Increment the bin corresponding to the x value by one.
> > >
> > >  (define (histogram-increment! h x)
> > >    (let ((n (histogram-n h))
> > >          (ranges (histogram-ranges h))
> > >          (bins (histogram-bins h))
> > >          (uniform-ranges? (histogram-ranges-uniform? h)))
> > >      (if uniform-ranges?
> > >          ;; Compute bin
> > >          (let ((i (inexact->exact
> > >                    (floor (/ (- x (vector-ref ranges 0))
> > >                              (/ (- (vector-ref ranges n)
> > >                                    (vector-ref ranges 0))
> > >                                 n))))))
> > >            (if (<= 0 i (- n 1))
> > >                (vector-set! bins i
> > >                             (+ (vector-ref bins i) 1))))
> > >          ;; Search for bin
> > >          (let/ec exit ;; <---------- line #219
> > >            (if (< x (vector-ref ranges 0))
> > >                (exit))
> > >            (do ((i 0 (+ i 1)))
> > >              ((= i n) (void))
> > >              (if (< x (vector-ref ranges (+ i 1)))
> > >                  (begin
> > >                    (vector-set! bins i
> > >                                 (+ (vector-ref bins i) 1))
> > >                    (exit))))))))
> > >
> > >
> > > Many Thanks,
> > > Vincent.
> > > _________________________________________________
> > >  For list-related administrative tasks:
> > >  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> > >
> >
> >
>
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