Numerics question

[kj]

Please disregard my ineptly posed question.

~K

In <i0l9f3$7d3$1 at reader1.panix.com> kj <no.email at please.post> writes:





>I define

>ninv = 1.0/n

>...where n is some integer, and I want to write some function f such
>that f(m * ninv) returns the smallest integer that is >= m * ninv,
>where m is some other integer.  And, in particular, if m is p*n
>for some integer p, then f((p*n) * ninv) should return the integer
>p.

>The first solution that comes to mind is something like

>def f(x):
>    return int(math.ceil(x))

>At first this seems to work:

>>>> f((7*2) * (1.0/2))
>7
>>>> f((7*3) * (1.0/3))
>7

>...but there are values of n for which it fails:

>>>> f((7*75) * (1.0/75))
>8

>The problem here is that, due to numerical error, the expression
>((7*75) * (1.0/75)) evaluates to a number *just* above 7.  The
>surrounding math.ceil then turns this into 8.0, etc.

>Is there a way to define f so that it behaves as expected?

>TIA!

>~K