Re: Help please, strange behavior

From:
"Victor Bazarov" <v.Abazarov@comAcast.net>
Newsgroups:
comp.lang.c++
Date:
Wed, 14 Feb 2007 14:37:01 -0500
Message-ID:
<eqvocu$g1m$1@news.datemas.de>
Simply_Red wrote:

On 14 f?v, 14:29, Rolf Magnus <ramag...@t-online.de> wrote:

Simply_Red wrote:

On 14 f?v, 14:12, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:

Simply_Redwrote:

i'm sorry i posted this in other groupes, and i didn't see it,
and as this group is most actif, i repost it here, and sorry for
mutliposting:

Hi,
i'm using VC6, i have this declaration:

typedef struct tagTLimite {
      double Debut;
      double Fin;
}Limites;

typedef struct TagElemTab {
      double NivY;
      bool Existe;
      std::vector<Limites> PtLimites;
}ElemTabCont;

void myfunc( )
{
.....
ElemTabCont * ContNonOrd;//contour non ordone
long nbNiveau = (yhi-ylo)/stepY +1 ;


What is the type of 'yhi', 'ylo', 'stepY'? What are their values?
What value do you get in 'nbNiveau'? What did you expect


yhi, ylo, stepY are doubles values: 16, 0, 0.1 respectively
I get 160 in nbNiveau, and I need 161.


double isn't precise either. Note that 0.1 in binary is a periodic
number that cannot be represented exactly. So instead of 0.1, you
get the closest representable value. As a result, you might get
something like 160.99999999998, which gets truncated to 160 when
converted to long.


but if 160.999999998 is truncated to 160, 159.99999998 must be
truncated to 159.....


Yes... And?

V
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