Re: Implementing rounding rule in plpgsql - Mailing list pgsql-general

From Michael Fuhr
Subject Re: Implementing rounding rule in plpgsql
Date
Msg-id 20051120154051.GA38669@winnie.fuhr.org
Whole thread Raw
In response to Re: Implementing rounding rule in plpgsql  (Michael Fuhr <mike@fuhr.org>)
List pgsql-general
On Sun, Nov 20, 2005 at 02:24:20AM -0700, Michael Fuhr wrote:
> On Sun, Nov 20, 2005 at 02:01:02AM -0500, jeff sacksteder wrote:
> > Due to application requirements, I need to implement a rounding function
> > that is independant of the baked-in rounding functionality. I'd prefer to do
> > it in plpgsql for maximum portability.
> > To do this, I'll need to sequentially walk through the digits of an
> > arbritarily long floating-point number. I can't think of a good way to do
> > this.
>
> This wouldn't be a homework assignment, would it?  Anyway, maybe
> this will give you some ideas:

It occurred to me after I posted this that there might be a numerical
method for walking through the digits.  Successive multiplication by
10 has problems due to the inaccuracies of floating-point arithmetic,
although using a numeric type instead of double precision might solve
that problem.  Maybe somebody more familiar with numerical methods
than I will suggest something.

--
Michael Fuhr

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