Re: Non-strictly Weak Sorting using STL?
On 9 Jan., 23:49, Andy Champ <no....@nospam.com> wrote:
peter koch wrote:
On 9 Jan., 21:22, Andy Champ <no....@nospam.com> wrote:
Donovan Parks wrote:
Hello,
I am interesting in performing a non-strictly weak sorting of a vecto=
r
of objects. Specifically, I wish to sort these objects by a double
field unless they are equal in which case I wish to sort them based o=
n
another field. As such, the ordering may no be strictly weak. Is it
possible to do this using STL?
I am using Visual C++ Express 2008 and it complains of a non-strictly
weak ordering when I run my program in debug mode. However, it will
let me do as I please in release mode. As an alternative, is there a
way to inform my compiler that I am OK with a non-strictly weak
ordering?
Thanks.
You want to define what you mean by "equal" in a double. A double i=
s a
(very close) approximation to a number; it's possible for 1+1 to no=
t be
exactly 2, but instead be 1.9999999999999999 or 2.00000000000000000001
(with a few more digits - usually)
Sorry, but that is just nonsense - and unrelated to the original post.
Actually, I do have a relevant point.
No.
He said "Specifically, I wish to
sort these objects by a double field unless they are equal". I wish to
point out that "equal" is not a reliable measure for floating point
numbers.
That is wrong.
Only when he has answered that is it worth considering
strictly weak ordering and the secondary key.
And this is also wrong.
/Peter