Re: Rounding of the double
On 31 May 2007 08:56:04 -0700, Alex <alsim123@hotmail.com> wrote:
I'd tried to use already Tom's link, I found it in some previous
posts. It doesn't work.
I'm calling RoundDouble( 0.80000000000000004, 4 )
At the end this function divides 80 by 100 and return of course
0.80000000000000004
So I think the problem is that "double" is also "float" in C++
It may sound stupid, but I'm going to use SQL Server to get the proper
result, it has type "numeric", if in SQL Server I divide numeric =
80.00, by numeric = 100.00 it returns correct result
0.80000000000000000
but if in SQL Server I divide float = 80.00, by float = 100.00 it
returns again result
0.80000000000000004
So SQL Server has numeric type and C++ doesn't. So I'll write some
SQL Server stored procedure, which will be using numeric data types.
It sounds like you're talking about a "decimal" type (e.g. BCD) vs.
(binary) "floating point" (e.g. the float and double types in C++). Be
aware there are an infinite number of reals that cannot be represented by
any finite number format, so the problem may well resurface in another
context no matter which format you choose.
--
Doug Harrison
Visual C++ MVP